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dana1981

Dana Nuccitelli is an environmental scientist at a private environmental consulting firm in the Sacramento, California area. He has a Bachelor's Degree in astrophysics from the University of California at Berkeley, and a Master's Degree in physics from the University of California at Davis. He has been researching climate science, economics, and solutions as a hobby since 2006, and has contributed to Skeptical Science since September, 2010.  He also blogs at The GuardianFollow him on Twitter.

Publications

Nuccitelli, D., Way, R., Painting, R., Church, J., & Cook, J. (2012). Comment on ocean heat content and Earth's radiation imbalance. II. Relation to climate shifts. Physics Letters A.

Cook, J., Nuccitelli, D., Green, S.A., Richardson, M., Winkler, B., Painting, R., Way, R., Jacobs, P., & Skuce, A. (2013). Quantifying the consensus on anthropogenic global warming in the scientific literature. Environmental Research Letters, 8(2), 024024+.

Benestad, R. E., Hygen, H. O., Dorland, R. V., Cook, J., & Nuccitelli, D. (2013). Agnotology: learning from mistakes. Earth System Dynamics Discussions, 4(1), 451-505.

Nuccitelli, D., Richter, M. J., & McCall, B. J. (2005). A search for interstellar carbon-60. In IAU Symposium (Vol. 235, p. 236P).

Encrenaz, T., Bézard, B., Greathouse, T., Holmes, S., Richter, M., Nuccitelli, D., & Forget, F. et al. (2006, February). Ground-based high-resolution IR spectroscopy of Mars: H2O and H2O2 mapping, search for CH4, and determination of CO2 isotopic ratios. In Second Workshop on Mars Atmosphere Modelling and Observations, held February.

 

Blog posts by dana1981


Climate contrarian backlash - a difficult lesson for scientific journals to learn

Posted on 14 April 2014 by dana1981 &

Scientific journals have had a bumpy road trying to learn how to deal with climate contrarians. Poor decisions by journal staff in dealing with contrarians have often led to editors resigning and a damaged reputation in the academic community.

The latest such example is the journal Frontiers and its response to bullying by contrarians over a paper by Stephan Lewandowsky and colleagues. The paper analyzed the conspiratorial psychology of contrarian comments made on public blogs. As I previously documented, Frontiers received a number of complaints from contrarians that this analysis of their public comments was libelous or defamatory, and the journal ultimately caved and decided to retract the paper.

In its investigation, Frontiers had found no academic or ethical problems with the paper, but was concerned about legal liabilities. The journal and paper authors contractually agreed to a retraction statement saying as much. However, perhaps in the face of criticism from the academic community for failing to support academically and ethically sound research, Frontiers later revised its statement to depart from the contractually agreed statement and shift all the blame to the authors, contradicting the contractually agreed upon statement.

This final move backfired and led to the resignation of three of the journal's editors, Ugo Bardi, Björn Brembs, and Colin Davis. Brembs' comments were particularly scathing,

"It is quite clear, why the content of the paper may feel painful to those cited in it, but as long as "conspiracist ideation" is not an official mental disorder, I cannot see any defamation. If you don't want to be labeled a conspiracy theorist, don't behave like one publicly on the internet. Therefore, after reading the paper, in my opinion, Frontiers ought to have supported their authors just as their home institution (UWA) is supporting them as their employees."

Robert Brulle, Professor of Sociology and Environmental Science at Drexel University has also informed me that as a result of the Recursive Fury incident, he has declined to write an article that Frontiers requested, and will no longer write or review for any Frontiers publications. The journal's reputation has undoubtedly taken a serious hit in the academic community for failing to stand behind sound research, and then trying to shift the blame to the authors of that research.

The Frontiers debacle is just the latest in a long history of interactions between contrarians and scientific journals that have not ended well for the latter. Unlike the Lewandowsky case, the previous examples involve the publication of contrarian research that's generally fundamentally flawed in peer-reviewed scientific journals, through one of the four approaches illustrated in the graphic below.

Ways contrarians get papers published in peer-reviewed journals Four ways in which flawed research gets published.

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14 comments


Climate imbalance – disparity in the quality of research by contrarian and mainstream climate scientists

Posted on 11 April 2014 by dana1981 &

A new paper has been published in the journal Cosmopolis entitled Review of the consensus and asymmetric quality of research on human-induced climate change. The paper was authored by John Abraham, myself, John Cook, John Fasullo, Peter Jacobs, and Scott Mandia. Each of the authors has experience in publishing peer-reviewed responses to flawed contrarian papers.

Despite the 97% expert consensus on human-caused global warming supported by peer-reviewed research, expert opinion, the IPCC reports, and National Academies of Science and other scientific organizations from around the world, a large segment of the population remains unconvinced on the issue. A new commentary by Edward Maibach, Teresa Myers and Anthony Leiserowitz in Earth's Future notes that most people don't know there is a scientific consensus about human-caused climate change, which undermines public engagement on the subject.

This 'consensus gap' is in large part due the media giving disproportionate coverage to climate contrarians. In our paper, we sought to evaluate whether that disproportionate media coverage was justified by examining how well contrarian hypotheses have withstood scientific scrutiny and the test of time. The short answer is, not well.

Low climate sensitivity papers by Lindzen and Spencer (open circles) and peer-reviewed rebuttals (closed circles).  Created by John Garrett of Wildomar, CA. Low climate sensitivity papers by Lindzen and Spencer (open circles) and peer-reviewed rebuttals (closed circles). Created by John Garrett of Wildomar, CA.

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7 comments


Fox News climate change coverage is now 28% accurate, up from 7%

Posted on 8 April 2014 by dana1981 &

The Union of Concerned Scientists (UCS) has just published an analysis of 2013 climate coverage by the three major American cable news networks. The report and data are available online, and the results are summarized in the figure below.

Cable news climate coverage accuracy

UCS reviewed nearly 600 segments mentioning "global warming" or "climate change" across the networks' most prominent evening and weekend programs during the 2013 calendar year. Segments that contained any inaccurate or misleading representations of climate science were categorized as misleading; otherwise they were characterized as being accurate.

UCS also put the misleading statements in sub-categories that reveal the problematic tendencies of each network's climate coverage. Aaron Huertas, a science communications officer at UCS who led the analysis said of the difference between network climate coverage,

"Sometimes, it's like the networks are covering different planets. Unfortunately, too many politicians, interest groups, and pundits continue to dispute established climate science and cable shows sometimes give them a platform to do so."

The UCS analysis found that Fox News Channel hosts and guests were the most likely to accuse scientists of manipulating or hiding climate data. Fox hosts and guests often conveyed misinformation about scientific findings, including many false claims that global warming is not occurring.

Types of misleading climate coverage on Fox News

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1 comments


The climate change uncertainty monster – more uncertainty means more urgency to tackle global warming

Posted on 5 April 2014 by dana1981 &

A new two-part study published in Climatic Change by a team of scientists led by Stephan Lewandowsky examines mathematically what happens to the risks posed by climate change when the scientific uncertainty increases. Part 1 of the study explores two important points.

First, the probable range of climate sensitivity to the increased greenhouse effect isn't symmetrical. Instead, based on the available evidence and research, it's more likely that we'll see a large amount of global warming than a small amount in response to rising carbon emissions. By itself, this means that more climate uncertainty translates into an even bigger risk of painful consequences than relatively benign consequences. More uncertainty means a slightly better chance of the low warming outcomes, but it also means an even bigger chance of the high warming outcomes, because the scientific data have a harder time ruling those out.

The second critical point is that economic models agree that once we reach a certain tipping point, the costs of climate damage increase at an accelerating rate. The models don't agree on exactly where that tipping point lies, but they do agree on the shape of the curve and the acceleration of the climate damage costs once we pass that tipping point (even the 'skeptics' agree on this).

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12 comments


Video: Climate science crash course by Dana Nuccitelli with Citizens Climate Lobby

Posted on 4 April 2014 by dana1981 &

On March 8th, 2014, I participated in a Faith and Climate Forum near Sacramento, California.  The event was co-sponsored by the Sacramento chapter of Citizens Climate Lobby (CCL), of which I'm a member.  CCL is a non-partisan grassroots organization whose goal is to build the political will to maintain a liveable climate, specifically through a revenue-neutral carbon tax. 

Another Sacramento CCL chapter member, Christine Bailey organized this event, bringing together local faith leaders and CCL members to speak about the importance of addressing climate change.  The event began with local leaders of various religions including Presbyterian, Buddhist, Islamic, and Jewish faiths speaking about the importance of preserving a liveable climate for each of their religions.  I was asked to follow these speakers to talk about the science, and I gave what I called 'a climate science crash course'.  Videographer Brian McKinsey recorded the event, and the whole thing can be viewed on his YouTube page.  My talk can be viewed below, and the Powerpoint slides can be downloaded here (8.5 MB, without Andy Lee Robinson's Arctic sea ice cubes video) and here (16.5 MB with the video).

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1 comments


IPCC report warns of future climate change risks, but is spun by contrarians

Posted on 31 March 2014 by dana1981 &

The Intergovernmental Panel on Climate Change has just published its latest Working Group II report detailing impacts, adaptation, and vulnerability associated with climate change. The picture it paints with respect to the consequences of continued climate change is rather bleak.

For example, the report discusses the risk associated with food insecurity due to more intense droughts, floods, and heat waves in a warmer world, especially for poorer countries. This contradicts the claims of climate contrarians like Matt Ridley, who have tried to claim that rising carbon dioxide levels are good for crops.

While rising carbon dioxide levels have led to 'global greening' in past decades and improved agricultural technology has increased crop yields, research has indicated that both of these trends are already beginning to reverse. While plants like carbon dioxide, they don't like heat waves, droughts, and floods. Likewise, economist Richard Tol has argued that farmers can adapt to climate change, but adaptation has its costs and its limits. In fact, the IPCC summary report notes that most studies project a decline in crop yields starting in 2030, even as global food demand continues to rise.

SPM.7

Summary of projected changes in crop yields, due to climate change over the 21st century. Yellow indicates studies that project crop yield decreases, blue indicates studies projecting increases. From IPCC AR5 WGII SPM.

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Cherry picked and misrepresented climate science undermines FiveThirtyEight brand

Posted on 25 March 2014 by dana1981 & Albatross

Nate Silver has launched a new FiveThirtyEight blog with the intent of applying his data-driven approach to a wide variety of subjects.  The problem is that Nate Silver is himself only one man, so FiveThirtyEight has hired a variety of contributors to write about the subjects that are outside his expertise and comfort zone.  For the topic of climate change, Silver decided to hire the renowned obfuscator Roger Pielke, Jr.

This was immediately disappointing for those familiar with Pielke's work, because FiveThirtyEight is a statistics site, and frankly Pielke is not good at statistics.  Instead, Pielke is known for taking a selective view of the peer-reviewed scientific literature in order to downplay the connection between human-caused global warming and extreme weather.  Predictably, Pielke's first two posts at FiveThirtyEight did exactly that, and included a litany of errors:

  • The headline and main point of his post are wrong.
  • He misrepresents his own research.
  • The references he provides don't say what he claims and don't support his argument.
  • Research he neglects contradicts his conclusions.
  • He doesn't include all available data.
  • He incorrectly claims that weather-related disasters aren't becoming more frequent.
  • He fails to account for the costs of improved technology and the damages they prevent.
  • He considers only land-falling hurricanes whose damages are highly variable.
  • His conclusions are contradicted by the increased intensity of North Atlantic hurricanes, and global warming's contribution to their storm surges and flooding.

Pielke vs. Munich Re

Pielke's first FiveThirtyEight post begins by plotting global disaster economic losses, from data provided by reinsurance company Munich Re.  Except for some reason Pielke only plots the data from 1990 to 2013, when Munich Re provides data beginning in 1980.

Munich Re disaster losses

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19 comments


Lessons from Past Climate Predictions: J.S. Sawyer in 1972

Posted on 19 March 2014 by dana1981 &

In the Lessons from Past Predictions series, we've examined some impressively accurate global warming projections made over 30 years ago, for example by James Hansen in 1981 and Wallace Broecker in 1975.  We recently learned of an even earlier successful prediction, made by John Stanley (J.S.) Sawyer in a paper published in Nature in 1972.

J.S. Sawyer was a British meteorologist born in 1916.  He was elected a Fellow of the Royal Society in 1962, and was also a Fellow of the Meteorological Society and the organization's president from 1963 to 1965.

His 1972 paper reveals how much we knew about the fundamental workings of the global climate over 40 years ago.  For example, Sawyer addressed the myth and misunderstanding that as a trace gas in the atmosphere, it may seem natural to assume that rising levels of carbon dioxide don't have much impact on the climate.  Sawyer wrote,

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13 comments


30 US Senators Speak Up4Climate Science

Posted on 14 March 2014 by dana1981 & Sarah

On the night of March 10th to the morning of March 11th, 30 US Senators stayed up all night speaking about climate change for 15 hours.  The event was the first hosted by the Senate Climate Action Task Force.  A video of the full session can be viewed courtesy of C-SPAN2, and is also searchable by speaker and keyword.

The event was encouraging not just because 30 percent of the members of the US Senate were willing to devote their personal time to discuss this critical subject, but also because they displayed a strong understanding of climate change and its impacts.  Senator Bernie Sanders (I-VT) invoked the 97 percent expert consensus on human caused global warming from Cook et al. (2013).

Senator Jeff Merkeley (D-OR) spoke about pine beetle population explosions decimating Oregon forests.  This is a result of warmer winters and thus fewer extreme cold events that normally act to limit pine beetle populations.

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4 comments


GWPF optimism on climate sensitivity is ill-founded

Posted on 10 March 2014 by dana1981 &

The UK anti-climate policy advocacy group Global Warming Policy Foundation (GWPF) has published a report written by Nic Lewis and Marcel Crok claiming “the IPCC hid the good news” regarding climate sensitivity.  Lewis is an amateur researcher and retired financier who has published a few papers estimating climate sensitivity, and Crok is a freelance science writer.

GWPF asked climate scientist Judith Curry to write the Foreword to the report, presumably to lend it more credibility.  However, Curry has no publications or expertise in this area, and once said that the global equilibrium climate sensitivity could fall anywhere between 0 and 10°C for doubled CO2.  This comment is totally incompatible with the body of climate sensitivity research, and also with the GWPF report.

The report itself is essentially a commentary and includes no new information.  It boils down to Lewis and Crok trying to make the case that climate sensitivity is on the lower end of the IPCC estimated range.  In the report, they find reasons to dismiss the many studies and varying approaches that arrive at higher climate sensitivity estimates, and fail to discuss the shortcomings of the lower sensitivity studies that they prefer.  In short, it’s a very selective and biased review of the scientific literature on the subject.  Recent papers by Gavin Schmidt and Drew Shindell at NASA GISS, not considered in the GWPF report, entirely contradict its conclusions, for example.

There are a few main methods to estimate the global climate sensitivity; Lewis and Crok focus on three of these and present their case for why each should be considered valid (when yielding low sensitivity results) or disregarded (when yieliding moderate or high sensitivity results).  Here we’ll look at each, including evidence the GWPF report failed to consider, and show that their conclusions are not supported when the full body of research is considered.  As climate scientist Steven Sherwood described it,

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46 comments


Cartoon: the climate contrarian guide to managing risk

Posted on 4 March 2014 by dana1981 & John Cook

Climate change is fundamentally a risk management problem.  Whether or not you agree with the 97 percent expert consensus on human-caused global warming, there is an undeniable risk that the consensus is correct and that we're causing dangerously rapid climate change.

Frequently, climate contrarians argue against taking action to mitigate that risk by claiming the uncertainties are too large.  One of the most visible figures to make this argument is climate scientist Judith Curry, who said in 2013,

"I can't say myself that [doing nothing] isn't the best solution."

This argument represents a failure to grasp the principles of basic risk management, as illustrated in the following cartoon.

When it comes to managing risk, uncertainty is not our friend.  Uncertainty means it's possible the outcome will be better than we expect, but it's also possible it will be much worse than we expect.  In fact, continuing with business-as-usual would only be a reasonable option in the absolute best case scenario. 

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77 comments


The epidemic of climate science false balance in the media

Posted on 27 February 2014 by dana1981 &

False balance in media reporting on climate change is a big problem for one overarching reason: there is a huge gap between the 97 percent expert consensus on human-caused global warming, and the public perception that scientists are evenly divided on the subject.

 The consensus gap

This can undoubtedly be traced in large part to the media giving disproportionate coverage to the opposing fringe climate contrarian views. Research has shown that people who are unaware of the expert consensus are less likely to accept the science and less likely to support taking action to address the problem, so media false balance can be linked directly to our inability to solve the climate problem.

The BBC is one such culprit, having repeatedly given climate contrarians disproportionate air time on its programs. Frequent recent BBC guests include blogger Andrew Montford and politician and founder of the anti-climate policy think tank Global Warming Policy Foundation, Nigel Lawson. The former was recently interviewed on BBC Radio 5 Live's Stephen Nolan show, together with climate scientist Paul Williams from the University of Reading. The latter was invited onto the BBC Radio 4 Today program alongside climate scientist Brian Hoskins from the Imperial College London and Royal Society.

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Nazis, shoddy science, and the climate contrarian credibility gap

Posted on 22 February 2014 by dana1981 &

Because the pool of climate experts who dispute that humans are the primary cause of global warming is so small, representing just 2 to 4 percent of climate scientists, climate contrarians often reference the same few contrarian scientists. Two such examples are Roy Spencer and John Christy of the University of Alabama at Huntsville (UAH), both of whom have testified before US Congress several times, and are often interviewed and quoted in the conservative media.

And because that pool of contrarian climate experts is so small, their credibility often seems indestructible. For example, Richard Lindzen has been wrong on essentially every position he's taken on major climate science issues over the past quarter century, and yet the conservative media continue to treat him as a foremost climate expert. Therefore, it's important to remind ourselves what these few climate scientist contrarians really believe, and whether their arguments have any scientific validity.

Yesterday, Roy Spencer took to his blog, writing a post entitled "Time to push back against the global warming Nazis". The ensuing Godwinian rant was apparently triggered by somebody calling contrarians like Spencer "deniers." Personally I tend to avoid use of the term, simply because it inevitably causes the ensuing discussion to degenerate into an argument about whether "denier" refers to Holocaust denial. Obviously that misinterpretation of the term is exactly what "pushed [Spencer's] button," as he put it.

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Vision Prize: scientists are worried the IPCC is underestimating sea level rise

Posted on 18 February 2014 by dana1981 &

The Vision Prize is an online survey of scientists about climate risk. It's an impartial and independent research platform for incentivized polling of experts on important scientific issues that are relevant to policymakers. Some of their previous survey results have found that about 90 percent of participating scientists believe that humans are the primary cause of global warming over the past 250 years.

In its latest survey, the Vision Prize asked participants questions about technologies to limit climate change, and about the latest IPCC report. Two of these questions asked about the likelihood that global average sea level will rise less than the IPCC lowest estimate (0.25 meters, or 10 inches), or more than the IPCC highest estimate (0.91 meters, or 3 feet) by 2100. These estimates are about 60 percent higher than in the 2007 IPCC report, which intentionally left out dynamic processes that cause effects like the calving of ice shelves into the ocean, because at the time they were not well understood. As expected, research has shown that the previous IPCC report underestimated the rate of sea level rise.

The Vision Prize results revealed that despite the much higher sea level rise estimates this time around, the survey participants are worried that the IPCC is still underestimating future sea level rise. 41 percent responded that it's likely or very likely that sea level rise will exceed the IPCC highest estimate, and 71 percent answering that it's at least as likely as not. Conversely, only 5 percent responded that it's likely sea level rise will be less than the IPCC lowest estimate, and 83 percent called this scenario unlikely.

Vision Prize sea level question answers

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MP Graham Stringer and CNN Crossfire are wrong about the 97% consensus on human-caused global warming

Posted on 14 February 2014 by dana1981 &

In May 2013, several Skeptical Science contributors published a paper showing that of peer-reviewed climate publications over the past 20 years that take a position on the cause of global warming, 97 percent agree that humans are responsible.  Since that paper was published, it's been met with extensive denialism

The reaction of denial is not surprising, because an expert consensus is a powerful thing.  People can't be expert in every subject, so we defer to the consensus of experts on many subjects.  For this reason, climate scientists are the most trusted sources of climate science information.  As we documented in our paper, research has also shown that when people are aware of the expert consensus on human-caused global warming, they're more likely to accept the science and support climate policy to address the problem. 

Hence, those who support the status quo and oppose efforts to reduce greenhouse gas emissions have long engaged in a disinformation campaign to misinform the public about the expert consensus.  Their efforts have been successful, as evidenced by the 'consensus gap' whereby the public believe scientists are split on the cause of global warming; a stark contrast to the reality of the 97 percent consensus.

consensus gap

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Unprecedented trade wind strength is shifting global warming to the oceans, but for how much longer?

Posted on 10 February 2014 by dana1981 &

Research looking at the effects of Pacific Ocean cycles has been gradually piecing together the puzzle explaining why the rise of global surface temperatures has slowed over the past 10 to 15 years.  A new study just published in Nature Climate Change, led by Matthew England at the University of New South Wales, adds yet another piece to the puzzle by examining the influence of Pacific trade winds.

While the rate of surface temperature warming has slowed in recent years, several studies have shown that the warming of the planet as a whole has not.  This suggests that the slowed surface warming is not due as much to external factors like decreased solar activity or more pollutants in the atmosphere blocking sunlight, but more due to internal factors shifting the heat into the oceans.  In particular, the rate at which the deep oceans have warmed over the past 10 to 15 years is unprecedented in the past half century.

Research led by Masahiro Watanabe of the Japanese Atmosphere and Ocean Research Institute suggests this is mainly due to more efficient transfer of heat to the deep oceans. Consistent with model simulations led by Gerald Meehl, Watanabe finds that we sometimes expect "hiatus decades" to occur, when surface air temperatures don't warm because more heat is transferred to the deep ocean layers.  A paper published last year by Yu Kosaka and Shang-Ping Xie from the Scripps Institution of Oceanography found that accounting for the changes in Pacific Ocean surface temperatures allowed their model to reproduce the slowed global surface warming over the past 10 to 15 years.  However, the mechanism causing these Pacific Ocean changes has remained elusive.

The new study published by Matthew England's team helps explain how and why more heat is being funneled into the deeper ocean layers.  The study indicates that a dramatic acceleration in equatorial trade winds, associated with a negative phase of a cycle called the Interdecadal Pacific Oscillation (IPO) has invigorated the circulation of the Pacific Ocean.  This has caused more heat from the surface to be mixed down into deeper ocean layers, while bringing cooler waters to the surface. The combination of these two processes cools global surface temperatures.  Like the rate at which heat is accumulating in the deep oceans, the recent strengthening of the trade winds is unprecedented, as the bottom frame in the figure below shows.

England 2014 figure 1

Top frame: Global surface temperature anomalies.  Bottom frame: Pacific wind stress anomalies.  From England et al. (2014).

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100 comments


2013 was the second-hottest year on record without an El Niño

Posted on 6 February 2014 by dana1981 &

According to the global surface temperate data set compiled by Kevin Cowtan & Robert Way, which achieves the best coverage of the rapidly-warming Arctic by filling in data gaps between temperature stations using a statistical method called kriging, 2013 was the 5th-hottest year on record (since 1850).  The top three hottest years (2010, 2005, and 2007) were influenced by El Niño events, which cause short-term warming of the Earth's atmosphere.

Over the past decade, we've seen less warming at the surface and more warming in the oceans.  This has been in large part due to a change in Pacific Ocean cycles.  We're currently in a cycle that tends to produce more La Niña than El Niño events, which has resulted in the oceans accumulating more heat, leaving less energy than normal to warm the atmosphere.  This in turn has led to the widespread myth that the slowed rate of increase of global surface temperatures means we no longer have to worry about global warming, or that its consequences won't be as bad as expected.

The fundamental flaw in this argument is that it neglects a key fact: cycles are cyclical.  In the '80s and '90s when the Pacific Ocean was in the previous phase of this cycle, we saw more El Niño events and more warming of global surface temperatures than the average of climate models projected.  However, we can separate out the short-term El Niño and La Niña influences from the human-caused global warming component in the simple manner first suggested by  Texas state climatologist John Nielsen-Gammon, shown in this animated graphic:

ENSO temp influence

Global surface temperature data from Cowtan & Way, separated into El Niño (red), La Niña (blue), and Neutral (black) years for 1966–2013, with linear trends plotted for each category.

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70 comments


Google Earth: how much has global warming raised temperatures near you?

Posted on 4 February 2014 by dana1981 &

Google Earth temp grid
The University of East Anglia has teamed up with Google to make surface temperature data easily accessible.

If you've ever wondered how much global warming has raised local temperatures in your area or elsewhere on the globe, the University of East Anglia Climatic Research Unit (UEA CRU) has just released a new interactive Google Earth layer that will let you answer this question with ease. UEA CRU is one of the scientific organizations that compile temperature data from around the world. Their temperature dataset over land is called CRUTEM4, and is one of the most widely used records of the climate system.

The new Google Earth format allows users to scroll around the world, zoom in on 6,000 weather stations, and view monthly, seasonal and annual temperature data more easily than ever before. Users can drill down to see some 20,000 graphs – some of which show temperature records dating back to 1850.

The move is part of an ongoing effort to make data about past climate and climate change as accessible and transparent as possible. Dr. Tim Osborn from UEA CRU said,

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Corrections to Curry's Erroneous Comments on Ocean Heating

Posted on 30 January 2014 by dana1981 & Rob Painting

Committed to the Cause Pause

Recently, Georgia Tech climate scientist Judith Curry, along with Texas A&M climate scientist Andrew Dessler, testified before a US Senate committee on the subject of climate change.  While Dessler's testimony was excellent and well-supported by the body of scientific evidence, Curry's contained a number of errors (i.e. see the Guardian on global warming attribution, Eli Rabett on Antarctic sea ice, and Tamino on Arctic warming and sea level rise, for starters).

Curry's main and most flawed argument was that information in the latest IPCC report should decrease our confidence in human-caused global warming; an argument she based in large part on the supposed global warming 'pause', which is itself a fictional creation.  While the warming of average global surface temperatures has slowed (though not nearly as much as previously believed), the overall amount of heat accumulated by the global climate has not, with over 90 percent being absorbed by the oceans.

A few days after her Senate testimony, Curry took to her blog to dispute these data, essentially arguing that the amount of heat absorbed by the oceans has also 'paused', which would then support her arguments.  However, in evaluating the ocean heat content data and scientific literature, Curry made a number of mistakes.  This gives us an excellent opportunity to properly evaluate the science on rising ocean heat content and see what it tells us.  The key points are:

  • The deep oceans are warming rapidly in every data set that measures them (including those referenced by Curry).
  • Sea levels are rising consistent with rapid ocean warming.
  • The rate of ocean warming is consistent with the global energy imbalance.
  • The geographic distribution of ocean warming is consistent with natural variability superimposed on a warming background state forced by the increased greenhouse effect.
  • The global warming 'pause' is a fictional product of wishful thinking.

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Warming oceans consistent with rising sea level & global energy imbalance

Posted on 29 January 2014 by dana1981 & Rob Painting

Key Points:
  • The ocean is quickly accumulating heat and is doing so at an increased rate at depth during the so-called “hiatus” – a period over the last 16 years during which average global surface temperatures have risen at a slower rate than previous years.
  • This continued accumulation of heat is apparent in ocean temperature observations, as well as reanalysis and modeling experiments, and is now supported by up-to-date assessments of Earth's energy imbalance. 
  • Another key piece of evidence is rising global sea level. The expansion of the oceans (as they warm) has contributed to 35–40% of sea level rise over the last two decades - providing independent corroboration of the increase in ocean temperatures.

The Deep Ocean Layers are Quickly Accumulating Heat

Recently there have been some widespread misconceptions about heat accumulation in the oceans, particularly in the deeper layers below 700 meters.  Balmaseda et al. (2013) was a key study on this subject, using ocean heat content data from the European Centre for Medium-Range Weather Forecasts' Ocean Reanalysis System 4 (ORAS4).  A reanalysis is a climate or weather model simulation of the past that incorporates data from historical observations.  In the case of ORAS4, this includes ocean temperature measurements from bathythermographs and the Argo buoys, and other types of data like sea surface height and surface temperatures.  Their study concluded that heat has increased in the deep oceans at an unprecedented rate in recent years, with approximately 30 percent being sequestered below 700 meters since the year 2000.

OHC

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71 comments


More global warming will be worse for the economy, says Copenhagen Consensus Center

Posted on 24 January 2014 by dana1981 &

The Copenhagen Consensus Center (oddly, located in Massachusetts) is a think tank headed by Bjorn Lomborg that advocates for what they consider "the best ways for governments and philanthropists to spend aid and development money." The group recently released a report that attempts to quantify the economic damage caused by various global problems, including climate change. Regarding climate change and its costs, the group states,

"Climate change is real and man-made ... After year 2070, global warming will become a net cost to the world, justifying cost-effective climate action."

The climate change section was written by Richard Tol, who is one among several economists who have developed what are known as "integrated assessment models," which combine climate and economic modeling to estimate the costs of climate change. The Copenhagen Consensus Center climate costs report focuses on the impacts to global gross domestic product (GDP), and the results from Tol's FUND model are illustrated in the figure below (averages are the black curves).

climate GDP costs

The global average, minimum and maximum total annual economic impact of climate change in the 20th and 21st century.  From the Copenhagen Consensus Center report.

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Climate scientist Dessler to US Senate: 'Climate change is a clear and present danger'

Posted on 20 January 2014 by dana1981 &

Last Thursday, the US Senate committee on environment & public works held a four-hour hearing to review President Obama's Climate Action Plan. The hearing began with statements from the committee members, and then proceeded with two expert panels. The first was comprised of administrators of government agencies that are key to implementing President Obama's Climate Action Plan, like EPA administrator Gina McCarthy. The second panel was comprised of climate science and policy experts.

Andrew Dessler, a climate scientist from Texas A&M University, was one of the expert climate science witnesses invited to testify. In his testimony, Dessler simply and clearly articulated what we know about climate change, and why he personally views it as "a clear and present danger." Dessler's main points were:

1. The climate is warming - not just the atmosphere, but also the oceans, which are rising as a result, and ice is melting.

2. Most of the recent warming is extremely likely due to emissions of carbon dioxide and other greenhouse gases by human activities. This is supported by overwhelming evidence and hence was a conclusion of the 2014 IPCC report.

3. Future warming could be large. Over the 21st century, if we continue with business-as-usual, the IPCC projects 2.6–4.8°C average global surface warming.

4. The impacts of this are profound. The virtually certain impacts include increasing temperatures, more frequent extreme heat events, changes in
the distribution of rainfall, rising seas, and the oceans becoming more acidic. There are numerous additional possible impacts as well.

Strangely, in her testimony, Georgia Tech climate scientist Judith Curry directly contradicted Dessler's second point, arguing that the 2014 IPCC report actually weakens scientists' confidence in human-caused global warming. Curry's evidence to support that assertion boiled down to arguing of a supposed 'lack of warming since 1998', discrepancies between models and observations during that time, a lower climate sensitivity range in the 2014 than the 2007 IPCC report, and the fact that Antarctic sea ice extent has increased.

However, Dessler was correct that the IPCC increased its confidence in human-caused global warming between 2007 and 2014. It did so because the scientific evidence that humans are the dominant cause of global warming over the past century grew significantly stronger in recent years.

human vs. natural

Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WS12, dark green), and Jones et al. 2013 (J13, pink).

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Global warming is being caused by humans, not the sun, and is highly sensitive to CO2, new research shows

Posted on 9 January 2014 by dana1981 &

Over the past few weeks, several important new papers related to human vs. natural climate change have been published.  These papers add clarity to the causes of climate change, and how much global warming we can expect in the future.

First, a paper published in the Journal of Climate by Jara Imbers, Ana Lopez, Chris Huntingford, and Myles Allen examines the recent IPCC statement that expressed with 95 percent confidence that humans are the main cause of the current global warming.  One of the main challenges in attributing the causes of global warming lies in the representation of the natural internal variability of the Earth's climate.  The study used two very different representations of natural variability.  The first model assumed that there is short persistence in the internal variability, therefore the  present climate is mostly determined by the recent past and there is a finite time scale beyond which the memory of the system is lost. The second model assumed that the climate's internal variability has long persistence and the  present climate is influenced by all the previous years with no finite time scale beyond which the memory of the system is lost.

The authors then combined each of these representations of natural variability with a statistical multiple regression approach to estimate the individual contributions of the various forcings (e.g. solar, volcanic, greenhouse gases) to the increase in average global surface temperature.  In each case, the study found that the greenhouse gas-global warming signal was statistically significant, supporting the robustness of the IPCC statement on human-caused global warming.  As lead author Jara Imbers told me,

"...we investigate two extreme cases of the plausible temporal structures of the internal variability, and we find that the anthropogenic signal is robust and significant."

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The Weekly Standard's Lindzen puff piece exemplifies the conservative media's climate failures

Posted on 6 January 2014 by dana1981 &

The conservative media may currently be the single biggest roadblock to addressing the threat posed by human-caused climate change. There is virtually no support for any sort of climate policy among Republicans in US Congress, because even acknowledging the reality of global warming guarantees a wave of attacks by the extreme right-wing of the Republican Party and a probable primary election challenge. This politicization of science has been caused in large part by the conservative media like Fox News, who treat climate change like a punch line.

Another conservative media outlet, The Weekly Standard has occasionally run articles encouraging the Republican Party to stop denying science and start engaging in constructive debate about the best climate solutions. Unfortunately, those types of constructive articles are the exception rather than the norm. Last week, The Weekly Standard instead ran a puff piece about contrarian climate scientist Richard Lindzen that embodied the fundamental problems in most conservative media coverage of climate change.

Richard Lindzen is one of the approximately 3 percent of climate scientists who believe the human influence on global warming is relatively small (though Lindzen is now retired, no longer doing scientific research). More importantly, he's been wrong about nearly every major climate argument he's made over the past two decades. Lindzen is arguably the climate scientist who's been the wrongest, longest.

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Hockey sticks to huge methane burps: Five papers that shaped climate science in 2013

Posted on 3 January 2014 by dana1981 &

This is a re-post from The Carbon Brief by Roz Pidcock

There's no doubt, 2013 was a busy year in climate science. As well as a bumper new climate report from the UN's official climate assessment body - the Intergovernmental Panel on Climate Change (IPCC) - a few bits of research caused quite a stir on their own.

We've cast our collective Carbon Brief mind back over the year to find the five science papers that had everybody talking.

1. What hockey stick graphs tell us about recent climate change

Using fossils, corals, ice cores and tree rings, a study in the journal Science in March became the first to take a 11,300-year peek back into earth's temperature history.

Shaun Marcott and colleagues showed global temperature rose faster in the past century than it has since the end of the last ice age, more than 11,000 years ago.

The story piqued the interest of The Times, The Independent, The Daily Mail and The Evening Standard. And as an extension of Michael Mann's iconic "hockey stick" graph, the paper attracted a good deal of attention from climate skeptic corners too.

Marcott Et Al ., (2013)_2

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2013 in Review: a Productive Year for Skeptical Science

Posted on 31 December 2013 by dana1981 &

2013 is coming to a close, and so we take a look back at some of the important climate-related events of our year.

Skeptical Science Makes Significant Scholarly Contributions

The Skeptical Science team published several high-impact papers this year, starting with the Cook et al. (2013) consensus paper, co-authored by nine Skeptical Science volunteers.  The paper showed that there is a 97% consensus in the peer-reviewed climate science literature that humans are causing global warming.  The paper has already been cited in a broad range of scholarly journals and made a big splash in the media, even being the subject of two presidential Tweets.  It was also the 11th-most talked about academic paper in 2013.

Kevin Cowtan and Robert Way later published an important paper showing that much of the slowed global surface warming was an artifact of poor global temperature station coverage, mainly in the Arctic.  Cowtan & Way (2013) has received extensive praise among scientists with relevant expertise due to the quality and importance of the paper.  Most recently, Richard Alley discussed their results in testimony to the Pennsylvania House of Representatives.

Nuccitelli et al. (2013) also debunked a paper by Akasofu that tried to blame global warming on a magical 'natural recovery' from the Little Ice Age.  As Nuccitelli et al. showed, climate changes must be caused by physical mechanisms, and Akasofu's argument lacked any physical basis.

Richardson (2013) demonstrated that the modern increase in atmospheric CO2 is entirely human-caused, debunking a paper by Humlum, Stordahl and Solheim that wrongly claimed otherwise.

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More misleading Congressional climate testimony

Posted on 26 December 2013 by dana1981 &

On December 11th, the US Congress Committee on Science, Space, and Technology (labeled by many the House Anti-Science Committee for the unscientific views of many of its Republican members) held a hearing on the link between climate change and extreme weather events. Unfortunately, like many such hearings, the purpose of the event appeared to be more about reinforcing preconceived notions than educating committee members. This was made clear by a simple examination of the invited witnesses.

The Republicans on the committee invited two witnesses, John Christy and Roger Pielke Jr. House Republicans regularly invite Christy to testify on climate issues, because he's one of the less than 3 percent of climate experts whose research indicates that the human contribution to global warming is relatively small. Christy also reliably provides factually inaccurate testimony at these hearings, and this time around was no exception. In fact, Christy led off his written testimony with the following myth:

"As the global temperature failed to warm over the past 15 years..."

John Christy and Roy Spencer compile satellite measurements of the temperature of the Earth's atmosphere at the University of Alabama at Huntsville (UAH). Their data set estimates the warming of the lowest layer of the Earth's atmosphere at 0.21°C over the past 15 years, so Christy's opening statement is in direct contradiction with his own data. New estimates of average global surface temperatures also put the value at about 0.21°C global surface warming over the past 15 years.

Additionally, the warming of the atmosphere only accounts for about 2 percent of the warming of the global climate, which as a whole has accumulated heat at a rate equivalent to 4 Hiroshima atomic bomb detonations per second over the past 15 years. Perhaps the House Republicans keep inviting Christy to testify because he tells them what they want to hear regardless of its factual accuracy.

Global heat accumulation from Nuccitelli et al. (2012)

Global heat accumulation from Nuccitelli et al. (2012)

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Merry Christmas and Happy Holidays from Skeptical Science

Posted on 25 December 2013 by dana1981 & John Cook

And from Santa Claus too.

Santa Coal

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Gavin Schmidt … Speaking up and Speaking Out

Posted on 20 December 2013 by dana1981 &

This is a re-post from Bruce Lieberman at Yale Forum on Climate Change & the Media

Climate researcher and blogger Gavin Schmidt offers scientists an alternative to ‘saying nothing, doing nothing, being nothing’. What are the ‘rules’ of engagement and why?


SAN FRANCISCO, CA., DEC. 12, 2013 — Gavin Schmidt, the NASA scientist and climate science blogger at the website RealClimate, had the late Stephen Schneider behind his left shoulder for much of his talk at the AGU meeting today.

They were video clips from Schneider’s lectures over decades. The Stanford University climate scientist was a passionate advocate for sober and reasoned discourse on the globe’s changing climate, and he often spoke out against dishonesty in the public sphere — whether by opinion-makers, politicians, fossil fuel interests, or news personalities.

“I realized that everything I wanted to say was said 20, 25 years ago by Steve,” said Schmidt, a researcher at NASA Goddard Institute for Space Studies in New York.

During his talk, “What should a climate scientist advocate for?” Schmidt offered fellow scientists a framework for how to think about being more public — or public at all — as an advocate for science and, most of all, integrity.

He began with the story of Schneider taking a stand against a column by Eugene Guccione in 1971 that misrepresented climate science. In a letter to the Times, Schneider fact-checked the column and then ended with a personal argument that more research was needed in climate science. “That’s advocacy!” Schmidt said.

Schmidt went on to show a list of activities and asked audience members to raise their hands if they considered a given activity advocacy to avoid. Among them:

“Scientists should communicate more about what they do and find.”

“Funding for scientific research should be a higher priority.”

“People should understand the basics of the greenhouse effect.”

“Global warming should be in the high school science curriculum.”

“Geoengineering should be seriously considered.”

As fewer hands went up, Schmidt declared, “All of these statements are normative.” In other words, they are expressions of advocacy.

Whether or not scientists should speak out on policy matters related to their fields continues to be controversial. Just this year, UK climate scientist Tamsin Edwards wrote in the Guardian that climate scientists should not advocate at all, Schmidt said.

Why is that?

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In pictures: cutting edge climate science, communication, and kittens from the 2013 AGU conference

Posted on 17 December 2013 by dana1981 &

The 46th annual American Geophysical Union (AGU) fall meeting was held last week in San Francisco. Over 22,000 Earth and space scientists converged on the Moscone Center to discuss the latest cutting edge science, much of it related to climate change. The only downside to the conference was the sheer volume of interesting talks, forcing attendees to choose the most relevant to their fields of research. However, many of last week's talks are available for online viewing, currently free using the promo code AGU13.

Climate Literacy and Communications

My colleague John Cook (@skepticscience) of the University of Queensland Global Change Institute gave three talks related to climate literacy and communications. In the first he discussed the success of our approach in combining traditional science communications channels (peer-reviewed journals and press releases) with modern channels like social media to communicate our result finding a 97 percent expert consensus on human-caused global warming in the peer-reviewed literature, with great success.

Similarly, I (@dana1981) presented a poster (which can be viewed in the ePosters) outlining effective methods to communicate science via social media, based on our consensus paper communications success. Cook also discussed communicating the rapid continuation of global warming in terms people can visualize, like 4 Hiroshima atomic bomb detonations per second. For those who prefer a cuddlier comparison, Cook converted this to units of kitten sneezes – 7.4 quadrillion per second.

When accounting for all heat accumulating in the climate system, global warming is proceeding at 7.4 quadrillion kitten sneezes per second.  Image created by John Cook at Skeptical Science. 

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Why is Antarctic sea ice growing?

Posted on 12 December 2013 by dana1981 &

This is a re-post of an article at The Conversation by Guy Williams from the University of Tasmania

Recently NASA reported that this year’s maximum wintertime extent of Antarctic sea ice was the largest on record, even greater than the previous year’s record.

This is understandably at odds with the public’s perception of how polar ice should respond to a warming climate, given the dramatic headlines of severe decline in Arctic summertime extent. But the “paradox of Antarctic sea ice” has been on climate scientists' minds for some time.

Continental v. sea ice

First off, sea ice is different to the “continental ice” associated with polar ice caps, glaciers, ice shelves and icebergs. Continental ice is formed by the gradual deposition, build up and compaction of snow, resulting in ice that is hundreds to thousands of metres thick, storing and releasing freshwater that influences global sea-level over thousands of years.

Sea ice, though equally important to the climate system, is completely different. It is the thin layer (typically 1-2m) of ice that forms on the surface of the ocean when the latter is sufficiently cooled enough by the atmosphere.

From there sea ice can move with the winds and currents, continuing to grow both by freezing and through collisions (between the floes that make up the ice cover). When the atmosphere, and/or ocean is suitably warm again, such as in spring or if the sea ice has moved sufficiently towards the equator, then the sea ice melts again.

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Global warming is unpaused and stuck on fast forward, new research shows

Posted on 10 December 2013 by dana1981 &

New research by Kevin Trenberth and John Fasullo of the National Center for Atmospheric Research investigates how the warming of the Earth's climate has behaved over the past 15 years compared with the previous few decades. They conclude that while the rate of increase of average global surface temperatures has slowed since 1998, melting of Arctic ice, rising sea levels, and warming oceans have continued apace.

The widespread mainstream media focus on the slowed global surface warming has led some climate scientists like Trenberth and Fasullo to investigate its causes and how much various factors have contributed to the so-called 'pause' or 'hiatus.' However, the authors note that while the increase in global temperatures has slowed, the oceans have taken up heat at a faster rate since the turn of the century. Over 90 percent of the overall extra heat goes into the oceans, with only about 2 percent heating the Earth's atmosphere. The myth of the 'pause' is based on ignoring 98 percent of global warming and focusing exclusively on the one bit that's slowed.

Focusing only on surface temperatures

Nevertheless, the causes of the slowed global surface temperature increase present an interesting scientific question. In examining changes in the activity of the sun and volcanoes, Trenberth and Fasullo estimated that they can account for no more than a 20 percent reduction in the Earth's energy imbalance, which is what causes global warming. Thus the cause of the slowed surface warming must primarily lie elsewhere, and ocean cycles are the most likely culprit.

Trenberth and Fasullo found that after the massive El Niño event in 1998, the Pacific Ocean appears to have shifted into a new mode of operation. Since that time, Trenberth's research has shown that the deep oceans have absorbed more heat than at any other time in the past 50 years.

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How do meteorologists fit into the 97% global warming consensus?

Posted on 2 December 2013 by dana1981 &

Several surveys have found relatively low acceptance of human-caused global warming amongst meteorologists. For example, a 2009 survey found that among Earth scientists, only economic geologists (47 percent) had lower acceptance of human-caused global warming than meteorologists (64 percent). A new paper by social scientists from George Mason University, the American Meteorological Society (AMS), and Yale University reports results from a survey of members of the AMS to determine the factors associated with their views on climate change.

Climate Scientists and Meteorologists, Apples and Oranges

Predictably, many climate contrarians have already misrepresented this paper. In fact, the Heartland Institute (of Unabomber billboard infamy) misrepresented the study so badly (and arguably impersonated the AMS in a mass emailing), the AMS executive director (who is a co-author of the paper) took the unusual step of issuing a public reprimand against their behavior.

The misrepresentations of the study have claimed that it contradicts the 97 percent expert consensus on human-caused global warming. The prior studies that have found this high level of consensus were based specifically on climate experts – namely asking what those who do climate science research think, or what their peer-reviewed papers say about the causes of global warming.

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Will extreme weather like super typhoon Haiyan become the new norm?

Posted on 20 November 2013 by dana1981 &

Typhoon Haiyan may have been the strongest storm ever recorded; a fact that has triggered an array of stories discussing its possible links to climate change.

Global Warming Fuels Hurricanes

Climate scientists are confident in three ways that climate change will make the impacts of hurricanes worse. First, global warming causes sea level rise, which amplifies storm surges and flooding associated with hurricanes. As a paper published in the Proceedings of the National Academy of Sciences by Aslak Grinsted and colleagues concluded,

"we have probably crossed the threshold where Katrina magnitude hurricane surges are more likely caused by global warming than not."

Second, as climate scientist Kevin Trenberth has noted, global warming has also increased the amount of moisture in the air, causing more rainfall and amplifying flooding during hurricanes.

Third, warmer oceans are fuel for hurricanes. Research has shown that the strongest hurricanes have grown stronger in most ocean basins around the world over the past several decades, and climate models consistently project that this trend will continue. Chris Mooney recently documented the past decade's worth of monster hurricanes around the world, and Jeff Masters estimates that 6 of the 13 strongest tropical cyclones on record at landfall have happened since 1998.

strongest cyclones at landfall

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Super Typhoon Haiyan: Realities of a Warmed World and Need for Immediate Climate Action

Posted on 16 November 2013 by dana1981 &

This is a re-post of an Eco Watch article by Michael Mann

It is with a heavy heart and a respectful hand that I write this. Super Typhoon Haiyan has only just passed, and the devastation cannot yet even be fully understood. With that in mind, please consider a donation to the Philippine Red Cross.

But that will only aid those impacted by this storm. Not the next. Or the one after that.

haiyan

Damage from Haiyan, Photo credit: Creative Commons, EU ECHO via Arlynn Aquino, 2013

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Global warming since 1997 more than twice as fast as previously estimated, new study shows

Posted on 13 November 2013 by dana1981 & Kevin C

A new paper published in The Quarterly Journal of the Royal Meteorological Society fills in the gaps in the UK Met Office HadCRUT4 surface temperature data set, and finds that the global surface warming since 1997 has happened more than twice as fast as the HadCRUT4 estimate. This short video abstract summarizes the study's approach and results.

The study, authored by Kevin Cowtan from the University of York and Robert Way from the University of Ottawa (who both also contribute to Skeptical Science), notes that the Met Office data set only covers about 84 percent of the Earth's surface. There are large gaps in its coverage, mainly in the Arctic, Antarctica, and Africa, where temperature monitoring stations are relatively scarce. These are shown in white in the Met Office figure below. Note the rapid warming trend (red) in the Arctic in the Cowtan & Way version, missing from the Met Office data set.

Met Office vs. Cowtan & Way (2013) surface temperature coverage and trends 
Met Office vs. Cowtan & Way (2013) surface temperature coverage and trends

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Cosmic rays fall cosmically behind humans in explaining global warming

Posted on 12 November 2013 by dana1981 &

For climate skeptics trying to find an alternative explanation for the global warming that's occurred over the past century, the sun and galactic cosmic rays have become a popular hypothesis. However, several recent scientific papers have effectively put the final nail in the cosmic rays-global warming coffin.

Galactic cosmic rays
are high energy particles originating from outside our solar system. Henrik Svensmark of the Danish National Space Institute is the main proponent of the hypothesis linking them to global climate change. The hypothesis goes like this:

1) Cosmic rays may be able to seed cloud formation.
2) If so, fewer cosmic rays reaching Earth means less cloud formation.
3) Fewer clouds reflecting sunlight means more solar radiation reaching the Earth's surface, and thus warming.

The sun's magnetic field deflects galactic cosmic rays, so if the sun is in a phase of high activity with a strong magnetic field, fewer cosmic rays will reach Earth. Hence if this hypothesis is correct, galactic cosmic rays will act to amplify the solar influence on the global climate, whether it be a cooling effect from low solar activity or warming from high solar activity.

This is a relatively new and interesting hypothesis, so it's become popular amongst climate contrarians as an alternative explanation to human-caused global warming. However, it's also been the subject of extensive scientific research over the past few years, and the hypothesis simply has not held up to scrutiny.

First, there's the obvious fact that cosmic rays cannot explain the recent global warming because solar activity and the amount of cosmic rays reaching the Earth's surface have remained flat on average over the past 60 years. The sun and cosmic rays could only be causing global warming if there were a long-term upward trend in solar activity and downward trend in cosmic rays reaching Earth. In fact, the number of cosmic rays reaching Earth has increased since 1990, and reached record levels in 2009 (one of the hottest years on record).

temp vs. cosmic rays

Annual average GCR counts per minute (blue - note that numbers decrease going up the left vertical axis, because lower GCRs should mean higher temperatures) from the Neutron Monitor Database vs. annual average global surface temperature (red, right vertical axis) from NOAA NCDC, both with second order polynomial fits.

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Fox News defends global warming false balance by denying the 97% consensus

Posted on 23 October 2013 by dana1981 &

A study published earlier this year in the journal Public Understanding of Science found that consumption of politically conservative media outlets like Fox News decreases viewer trust in scientists, which in turn decreases belief that global warming is happening. This is in large part a result of disproportionate representation of the less than 3 percent of climate scientists who are 'skeptical' of human-caused global warming, as well as interviewing climate contrarian non-experts, for example from conservative fossil fuel-funded think tanks.

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Why trust climate models? It’s a matter of simple science

Posted on 22 October 2013 by dana1981 &

This is a re-post of an Ars Technica article by Scott K Johnson.

Model simulation showing average ocean current velocities and sea surface temperatures near Japan.  Source: IPCC

Talk to someone who rejects the conclusions of climate science and you’ll likely hear some variation of the following: “That’s all based on models, and you can make a model say anything you want.” Often, they'll suggest the models don't even have a solid foundation of data to work with—garbage in, garbage out, as the old programming adage goes. But how many of us (anywhere on the opinion spectrum) really know enough about what goes into a climate model to judge what comes out?

Climate models are used to generate projections showing the consequences of various courses of action, so they are relevant to discussions about public policy. Of course, being relevant to public policy also makes a thing vulnerable to the indiscriminate cannons on the foul battlefield of politics.

Skepticism is certainly not an unreasonable response when first exposed to the concept of a climate model. But skepticism means examining the evidence before making up one’s mind. If anyone has scrutinized the workings of climate models, it’s climate scientists—and they are confident that, just as in other fields, their models are useful scientific tools.

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Does the global warming 'pause' mean what you think it means?

Posted on 18 October 2013 by dana1981 &

In their study of media coverage of the 2013 Intergovernmental Panel on Climate Change (IPCC) report, Media Matters for America found that nearly half of print media stories discussed that the warming of global surface temperatures has slowed over the past 15 years. While this factoid is true, the question is, what does it mean?

Many popular climate myths share the trait of vagueness. For example, consider the argument that climate has changed naturally in the past. Well of course it has, but what does that tell us? It's akin to telling a fire investigator that fires have always happened naturally in the past. That would doubtless earn you a puzzled look from the investigator. Is the implication that because they have occurred naturally in the past, humans can't cause fires or climate change?

The same problem applies to the 'pause' (or 'hiatus' or better yet, 'speed bump') assertion. It's true that the warming of average global surface temperatures has slowed over the past 15 years, but what does that mean? One key piece of information that's usually omitted when discussing this subject is that the overall warming of the entire climate system has continued rapidly over the past 15 years, even faster than the 15 years before that.

Energy accumulation in within distinct components of Earth’s climate system from 1971–2010.  From the 2013 IPCC report.

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Two degrees: how we imagine climate change

Posted on 14 October 2013 by dana1981 &

This is a re-post of a The Conversation article by David Holmes.

Two degrees – the temperature rise we need to stay under to avoid catastrophic effects of climate change – is now the catch cry for global warming. Governments and numerous NGOs have eagerly adopted the limit; whether we can meet the target is another matter. But 2C isn’t an easy concept to grasp. So, how can we imagine what 2C means for the world?

First, why is 2C so significant? At any time of the year, for most latitudes at which people live, the difference between overnight lows and daytime high temperatures can be as much as 15C. In summer it is even greater. When the day to day temperatures of weather vary so much, 2C seems insignificant.

What we’re talking about here, though, is the global average temperature, not daily variations – and we’re fast approaching 2C warmer than before the industrial revolution and emissions from fossil fuels intensified. With feedbacks, such as increased water vapour (which is a powerful greenhouse gas), loss of reflective ice surface, and potential methane pulses (a greenhouse gas 20-times more powerful than CO2), 2C could be reached before 2060.

But it’s very difficult for people to imagine what a change in average temperature of 2C means for the planet as a whole, because of that daily variation.

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Why Curry, McIntyre, and Co. are Still Wrong about IPCC Climate Model Accuracy

Posted on 4 October 2013 by dana1981 &

Earlier this week, I explained why IPCC model global warming projections have done much better than you think.  Given the popularity of the Models are unreliable myth (coming in at #6 on the list of most used climate myths), it's not surprising that the post met with substantial resistance from climate contrarians, particularly in the comments on its Guardian cross-post.  Many of the commenters referenced a blog post published on the same day by blogger Steve McIntyre

McIntyre is puzzled as to why the depiction of the climate model projections and observational data shifted between the draft and draft final versions (the AR5 report won't be final until approximately January 2014) of Figure 1.4 in the IPCC AR5 report.  The draft and draft final versions are illustrated side-by-side below.

I explained the reason behind the change in my post.  It's due to the fact that, as statistician and blogger Tamino noted 10 months ago when the draft was "leaked," the draft figure was improperly baselined.  

draft vs draft final IPCC AR5 Fig 1.4

IPCC AR5 Figure 1.4 draft (left) and draft final (right) versions. In the draft final version, solid lines and squares represent measured average global surface temperature changes by NASA (blue), NOAA (yellow), and the UK Hadley Centre (green). The colored shading shows the projected range of surface warming in the IPCC First Assessment Report (FAR; yellow), Second (SAR; green), Third (TAR; blue), and Fourth (AR4; red).

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IPCC model global warming projections have done much better than you think

Posted on 1 October 2013 by dana1981 &

The figure below from the 2013 Intergovernmental Panel on Climate Change (IPCC) report compares the global surface warming projections made in the 1990, 1995, 2001, and 2007 IPCC reports to the temperature measurements.

IPCC AR5 Figure 1.4.  Solid lines and squares represent measured average global surface temperature changes by NASA (blue), NOAA (yellow), and the  UK Hadley Centre (green).  The colored shading shows the projected range of surface warming in the IPCC First Assessment Report (FAR; yellow), Second (SAR; green), Third (TAR; blue), and Fourth (AR4; red). 
IPCC AR5 Figure 1.4. Solid lines and squares represent measured average global surface temperature changes by NASA (blue), NOAA (yellow), and the UK Hadley Centre (green). The colored shading shows the projected range of surface warming in the IPCC First Assessment Report (FAR; yellow), Second (SAR; green), Third (TAR; blue), and Fourth (AR4; red).

Since 1990, global surface temperatures have warmed at a rate of about 0.15°C per decade, within the range of model projections of about 0.10 to 0.35°C per decade. As the IPCC notes,

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Why is the IPCC AR5 so much more confident in human-caused global warming?

Posted on 27 September 2013 by dana1981 &

Skeptical Science has launched a new feature, a collection of debunkings of the most popular myths about the IPCC. This post has been adapted into a rebuttal of the myth "IPCC human-caused global warming attribution confidence is unfounded". The short URL for this new resource is http://sks.to/ipcc

The fifth Intergovernmental Panel on Climate Change (IPCC) report states with 95 percent confidence that humans are the main cause of the current global warming. Many media outlets have reported that this is an increase from the 90 percent certainty in the fourth IPCC report, but actually the change is much more significant than that. In fact, if you look closely, the IPCC says that humans have most likely caused all of the global warming over the past 60 years.

Spot the Differences

Here is the relevant statement from the fourth IPCC report in 2007:

"Most of the observed increase in global average temperatures since the mid-20th century is very likely [90 percent confidence] due to the observed increase in anthropogenic greenhouse gas concentrations

Now here is the statement from the fifth IPCC report:

"It is extremely likely [95 percent confidence] more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together."

Did you spot the differences? The 2007 IPCC statement focused on human greenhouse gas emissions, while the 2013 statement pertains to all human influences on the climate. This includes the cooling effect from human aerosol emissions (pollutants that scatter sunlight).

Cooling from human aerosol emissions offsets about one-third of the warming from human greenhouse gas emissions. The new IPCC statement says that even taking that aerosol cooling effect into account, humans are still the main cause of the global warming over the past 60 years.

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Nuccitelli et al. (2013) Debunks Akasofu’s Magical Thinking

Posted on 23 September 2013 by dana1981 & John Abraham

One of the most important concepts to understand when trying to grasp how the Earth’s climate works, is that every climate change must have a physical cause.  This principle was the basis of our new paper, Nuccitelli et al. (2013).

For example, we know the increased greenhouse effect is creating a global energy imbalance that will cause the Earth's surface temperature to rise.  Any alternative explanation has to identify why the increased greenhouse effect isn't causing the warming we expect based on fundamental physics, and why the climate change 'fingerprints' are consistent with the increased greenhouse effect.

fingerprints

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Arctic sea ice "recovers" to its 6th-lowest extent in millennia

Posted on 19 September 2013 by dana1981 &

As Suzanne Goldenberg reported in The Guardian yesterday, Arctic sea ice appears to have reached its annual minimum extent, at approximately 5.1 million square kilometers. This is the 6th-lowest extent since the satellite record began in 1979.

But in fact, scientists have also reconstructed Arctic sea ice extent data much further into the past. For example, Walsh & Chapman from the University of Illinois have estimated sea ice extent as far back as the year 1870 using a vast array of data (for example, records kept by the Danish Meteorological Institute and Norwegian Polar Institute, and reports made from ocean vessels). While climate contrarians will sometimes try to argue that Arctic sea ice extent may have reached similar lows to today's in the 1920s or 1930s–1940s, the data compiled by Walsh & Chapman tell a very different story.

Average July through September Arctic sea ice extent 1870–2008 from the University of Illinois (Walsh & Chapman 2001 updated to 2008) and observational data from NSIDC for 2009–2013.  

Average July through September Arctic sea ice extent 1870–2008 from the University of Illinois (Walsh & Chapman 2001 updated to 2008) and observational data from NSIDC for 2009–2013.

Going back even further in time, a study published in the journal Nature in 2011 used a combination of Arctic ice core, tree ring, and lake sediment data to reconstruct Arctic conditions going back 1,450 years. The result is shown below.

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Latest myth from the Mail on Sunday on Arctic ice

Posted on 18 September 2013 by dana1981 &

This is Peter Hadfield's latest video, debunking David Rose's delusional Arctic sea ice article.

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The 5 stages of climate denial are on display ahead of the IPCC report

Posted on 16 September 2013 by dana1981 &

The fifth Intergovernmental Panel on Climate Change (IPCC) report is due out on September 27th, and is expected to reaffirm with growing confidence that humans are driving global warming and climate change. In anticipation of the widespread news coverage of this auspicious report, climate contrarians appear to be in damage control mode, trying to build up skeptical spin in media climate stories. Just in the past week we've seen:

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Arctic sea ice delusions strike the Mail on Sunday and Telegraph

Posted on 13 September 2013 by dana1981 &

When it comes to climate science reporting, the Mail on Sunday and Telegraph are only reliable in the sense that you can rely on them to usually get the science wrong. This weekend's Arctic sea ice articles from David Rose of the Mail and Hayley Dixon at the Telegraph unfortunately fit that pattern.

Both articles claimed that Arctic sea ice extent grew 60 percent in August 2013 as compared to August 2012. While this factoid may be technically true (though the 60 percent figure appears to be an exaggeration), it's also largely irrelevant. For one thing, the annual Arctic sea ice minimum occurs in September – we're not there yet. And while this year's minimum extent will certainly be higher than last year's, that's not the least bit surprising. As University of Reading climate scientist Ed Hawkins noted last year,

"Around 80% of the ~100 scientists at the Bjerknes [Arctic climate science] conference thought that there would be MORE Arctic sea-ice in 2013, compared to 2012."

Regression toward the Mean

The reason so many climate scientists predicted more ice this year than last is quite simple. There's a principle in statistics known as "regression toward the mean," which is the phenomenon that if an extreme value of a variable is observed, the next measurement will generally be less extreme. In other words, we should not often expect to observe records in consecutive years. 2012 shattered the previous record low sea ice extent; hence 'regression towards the mean' told us that 2013 would likely have a higher minimum extent.

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Debunking 97% Climate Consensus Denial

Posted on 9 September 2013 by dana1981 &

Communicating the expert consensus is very important in terms of increasing public awareness of human-caused climate change and support for climate solutions.  Thus it's perhaps not surprising that Cook et al. (2013) and its 97% consensus result have been the subject of extensive denial among the usual climate contrarian suspects.  After all, the fossil fuel industry, right-wing think tanks, and climate contrarians have been engaged in a disinformation campaign regarding the expert climate consensus for over two decades.  For example, Western Fuels Association conducted a half-million dollar campaign in 1991 designed to ‘reposition global warming as theory (not fact).’

The 97% Consensus is a Robust Result

Nevertheless, the existence of the expert consensus on human-caused global warming is a reality, as is clear from an examination of the full body of evidence.  For example, Naomi Oreskes found no rejections of the consensus in a survey of 928 abstracts performed in 2004Doran & Zimmerman (2009) found a 97% consensus among scientists actively publishing climate research.  Anderegg et al. (2010) reviewed publicly signed declarations supporting or rejecting human-caused global warming, and again found over 97% consensus among climate experts.  Cook et al. (2013) found the same 97% result through a survey of over 12,000 climate abstracts from peer-reviewed journals, as well as from over 2,000 scientist author self-ratings, among abstracts and papers taking a position on the causes of global warming.

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The Pacific Ocean fills in another piece of the global warming puzzle, and puzzles Curry

Posted on 3 September 2013 by dana1981 &

A new study published in the journal Nature incorporates temperature changes in the tropical Pacific Ocean into an advanced climate model, and finds that the model can reproduce observed global surface temperature changes remarkably well.

This graph shows the good match between model temperatures in the last few decades (in red) and measured temperatures (in black). Just accounting for radiative changes doesn't reproduce the recent surface warming slowdown (in purple). 

This graph shows the good match between temperatures in the Nature paper model (in red) and measured temperatures (in black). Just accounting for human and solar climate influences doesn't reproduce the recent surface warming slowdown (in purple).

Importantly, as authors Yu Kosaka and Shang-Ping Xie from the Scripps Institution of Oceanography explain, accounting for the changes in the Pacific Ocean allows the model to reproduce the slowed global surface warming over the past 15 years. It also accurately reproduces the regional and seasonal changes in surface temperatures, which adds confidence that their results are meaningful.

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Study offers clues on 20th century global warming wobbles

Posted on 2 September 2013 by dana1981 &

This is a re-post of an article on The Conversation by Sunanda Creagh and Merran Reed with an interview of John Cook

The amount of solar radiation passing through Earth’s atmosphere and reaching the ground globally peaked in the 1930s, substantially decreased from the 1940s to the 1970s, and changed little after that, a new study has found.

The study, published in the journal Proceedings of the National Academy of Sciences, found that “neither the rapid increase in temperature from the 1970s through the 1990s nor the slowdown of warming in the early 21st century appear to be significantly related to changes of Rs (solar radiation reaching the Earth’s surface)”.

The new finding may help explain variations in warming during the 20th century. The authors showed that, while aerosols and clouds did play some role in temperature variations, they did not have a major effect on global mean land temperatures after 1985.

The authors, Kaicun Wang from Beijing Normal University and Robert E. Dickinson from the University of Texas at Austin, compiled a global data set of daily temperatures from the 1900s and through to 2010.

They analysed the relationship between the amount of solar radiation reaching the Earth and diurnal temperature range (the daily temperature variations that occur as day turns into night).

The authors of the study said that “the overall increase of global temperature over the last century has been largely attributable to the increase of greenhouse gases. Less well understood are the reasons for the variability of this increase on a decadal time scale… However, global temperatures do not appear to be significantly affected by changing Rs (solar radiation reaching the Earth’s surface).”

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Coumou & Robinson on Extreme Heat: Choose Your Own Adventure

Posted on 21 August 2013 by dana1981 &

Dim Coumou and Alexander Robinson from the Potsdam Institute for Climate Impact Research have published a paper in Environmental Research Letters (open access, free to download) examining the frequency of extreme heat events in a warming world. 

They compared a future in which humans continue to rely heavily on fossil fuels (IPCC scenario RCP8.5) to one in which we transition away from fossil fuels and rapidly reduce greenhouse gas emissions (RCP2.6).  In both cases, the global land area experiencing extreme summer heat will quadruple by 2040 due to the global warming that's already locked in from the greenhouse gases we've emitted thus far.  However, in the low emissions scenario, extreme heat frequency stabilizes after 2040 (left frames in Figure 1), while it becomes the new norm for most of the world in a high emissions scenario (right frames in Figure 1).

extreme heat in the future

Figure 1: Multi-model mean of the percentage of boreal summer months in the time period 2071–2099 with temperatures beyond 3-sigma (top) and 5-sigma (bottom) under RCP2.6 (left) and RCP8.5 (right).

Rare 3-Sigma and 5-Sigma Events

Coumou & Robinson looked at the frequency of 3-sigma and 5-sigma temperature events.  For a normal distribution, 3-sigma represents a 1-in-370 event, and 5-sigma is a 1-in-1.7 million event.  In short, 3-sigma events are rare, and 5-sigma events are extremely rare.  In this paper, sigma (the standard deviation) is calculated based on temperatures over the past 60 years (1951–2010).

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A vicious cycle: Could droughts and storms make climate change worse?

Posted on 15 August 2013 by dana1981 &

This is a re-post of an article by Roz Pidcock at Carbon Brief

With climate change expected to bring more heatwaves, violent storms and heavy rainfall, the impact on human society is likely to be significant. As if we didn't have enough to adapt to, a new paper suggests extreme weather could further contribute to rising carbon dioxide levels by reducing how much carbon plants draw out of the air.

Growing plants take carbon dioxide out of the atmosphere and store it as living plant matter. The world's ecosystems have absorbed about a third of the carbon dioxide humans have put into the atmosphere through fossil fuel burning.In effect, by reducing the amount of carbon dioxide in the atmosphere, plants keep global temperature below what it might otherwise be.

The new paper suggests extreme weather events - such as heatwaves, droughts , storms and fires - weaken ecosystems' ability to act as a buffer against climate change.And the situation is likely to worsen as temperatures continue to rise and such extreme events become more frequent or more severe, the authors say.

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A grand solar minimum would barely make a dent in human-caused global warming

Posted on 14 August 2013 by dana1981 &

The Maunder Minimum was a period of very low solar activity between 1645 and 1715, and the Dalton Minimum was a period of low (but not as low as the Maunder Minimum) solar activity between 1790 and 1830.  Solar research suggests that we may have a similar period of low solar activity sometime this century.

minima sunspots

400 years of sunspot observations data, via Wikipedia

Recent articles in the Danish newspaper Jyllands-Posten (translation available here) and in the Irish Times both ran headlines claiming that another grand solar minimum could potentially trigger an "ice age" or "mini ice age" this century. These articles actually refer to the Little Ice Age (LIA) – a period about 500 to 150 years ago when global surface temperatures were about 1°C colder than they are today

Thus a grand solar minimum would have to cause about 1°C cooling, plus it would have to offset the continued human-caused global warming between 1 and 5°C by 2100, depending on how our greenhouse gas emissions change over the next century.  Though in the Jyllands-Posten article, Henrik Svensmark (the main proponent of the galactic cosmic ray-climate hypothesis) was a bit more measured, suggesting,

"I can imagine that it will become 0.2°C colder.  I would be surprised if it became 1–2°C"

So these two articles are suggesting that a grand solar minimum could have a cooling effect of about 1 to 6°C, depending on how human greenhouse gas emissions change over the next century. Is it plausible that a grand solar minimum could make that happen?

The short answer is, 'No.'

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What makes ice sheets grow and shrink?

Posted on 13 August 2013 by dana1981 &

This is a re-post of a Carbon Brief article by Freya Roberts

A new look at how the earth freezes and thaws suggests that while colder glacial periods in earth's history are triggered by changes in the planet's orbit, it takes climate feedbacks to give a full picture of why the planet freezes and thaws every hundred millennia.

The last million years

Earth has cycled between glacial and interglacial periods roughly every 100,000 years out of the past million. When the climate cools, vast ice sheets grow slowly from the north pole towards the equator, burying much of North America, Europe and Asia. When earth warms again, these continent-sized ice sheets melt quickly and retreat towards the poles.

Scientists previously thought that this cycle is caused by variations in the amount of solar energy reaching earth. A scientist named Milankovitch came up with the idea in 1941. He suggested that changes in earth's rotation, tilt and orbit all affect the distance between the sun and the planet, changing how warm it is in a small but significant way, on a timescale of tens of thousand to hundreds of thousand years.

But according to the authors of a new study in Nature, these cycles alone aren't enough to explain how vast ice sheets grow and shrink from glacial to interglacial.

Climate feedbacks

The Nature authors suggest that to understand why vast ice sheets grow and shrink, you need to look at climate feedbacks - natural processes that interact and amplify the changes in the amount of solar energy reaching earth.

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Reflections on a changing Arctic: Less ice means faster warming

Posted on 9 August 2013 by dana1981 &

This is a re-post of a Carbon Brief article by Roz Pidcock

The Arctic is intricately linked to earth's climate. As Arctic sea ice declines, the effects are being felt far beyond the Arctic region. Now a new study shows how losing sea ice means the top of the planet is absorbing more heat than it did just three decades ago - and it makes for a sobering read.

Scientists have noticed big changes in the Arctic since satellites started observing earth from space, thirty years ago. The area covered by sea ice is getting smaller and the ice is getting  thinner, due largely to  rising global temperature.

The loss is most noticeable at the end of summer, when sea ice shrinks to a minimum, as part of its seasonal cycle. In September 2012, Arctic sea ice reached its lowest extent since satellite records began.

Knock-on effects

Losing sea ice has  knock on effects for climate. One of the most direct consequences is that losing sea ice changes something scientists call albedo. Albedo is a measure of how well the earth's surface reflects sunlight.

Snow-covered sea ice has a high albedo, reflecting up to 85 per cent of sunlight. As the area covered by ice and snow gets smaller, sunlight that would have been reflected is  absorbed by open water instead, warming it up.

Albedo

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Fox News found to be a major driving force behind global warming denial

Posted on 8 August 2013 by dana1981 &

A new study published in the journal Public Understanding of Science (PDF available here) surveyed a nationally representative sample of over 1,000 Americans in 2008 and 2011 about their media consumption and beliefs about climate change.

The results suggest that conservative media consumption (specifically Fox News and Rush Limbaugh) decreases viewer trust in scientists, which in turn decreases belief that global warming is happening. In contrast, consumption of non-conservative media (specifically ABC, CBS, NBC, MSNBC, CNN, NPR, The New York Times, and The Washington Post) increases consumer trust in scientists, and in turn belief that global warming is happening.

The study also examined previous research on this issue and concluded that the conservative media creates distrust in scientists through five main methods:

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An accurately informed public is necessary for climate policy

Posted on 29 July 2013 by dana1981 &

Last week, the University of Nottingham Making Science Public blog published a guest post by Ben Pile, What’s behind the battle of received wisdoms?, which focused on Andrew Neil’s interview with Ed Davey on BBC Sunday Politics and my articles at The Guardian discussing the scientific errors Neil made on the show and in a subsequent BBC blog post.  This is a re-post of my guest post response.

Response to Professor Hulme’s Comments

Before addressing this post, I would like to respond to some comments made by Professor Mike Hulme regarding a paper I co-authored, Quantifying the consensus on anthropogenic global warming in the scientific literature, which was one of the topics discussed on Sunday Politics and in Pile’s post.  Professor Hulme said,

“It seems to me that these people are still living (or wishing to live) in the pre-2009 world of climate change discourse. Haven’t they noticed that public understanding of the climate issue has moved on?”

With all due respect to Professor Hulme, his perception of the public understanding of climate science is not reflected in the polling data.  In fact, we discussed this in our paper (which is open access and free to download),

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A tale told in maps and charts: Texas in the National Climate Assessment

Posted on 26 July 2013 by dana1981 &

This is a partial re-post from Texas Climate News

heat drought

Off the chart: The new National Climate Assessment contains numerous references to Texas' record-setting heat and drought in 2011. Those harsh conditions – the large red dot on this chart – "represent conditions far outside those that have been registered since the instrumental record began" in the 19th century, the report says. "Generally," it adds, "the changes in climate are increasing the likelihood for these types of severe events."

By Bill Dawson
Texas Climate News 

Expert authors: 240. Number of pages: 1,146.

Those two numbers convey a sense of the scope of the scientific effort that went into a new federally-comissioned report on climate change, issued last month in draft form. The study “collects, integrates, and assesses observations and research from around the country, helping to show what is actually happening and what it means for peoples’ lives, livelihoods, and future.”

The first paragraph of the National Climate Assessment – the first updated edition of that congressionally-ordered study in four years – conveys a sense of its sweeping findings:

Climate change is already affecting the American people. Certain types of weather events have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts. Sea level is rising, oceans are becoming more acidic, and glaciers and arctic sea ice are melting. These changes are part of the pattern of global climate change, which is primarily driven by human activity.

Katharine Hayhoe, director of the Climate Science Center at Texas Tech University and a lead author of one chapter in the report, told the Associated Press: “There is so much that is already happening today. This is no longer a future issue. It’s an issue that is staring us in the face today.”

And it will continue to do so in coming years and decades, the report stresses:

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The climate change policy discussion I wish Andrew Neil would have on BBC

Posted on 23 July 2013 by dana1981 &

On the BBC program Sunday Politics, Andrew Neil hosted UK Energy and Climate Change Secretary Ed Davey for a discussion about climate science and policy. In the process, Neil made a variety of errors in discussing climate science that I subsequently detailed. Neil responded in turn on his blog, admitting one mistake but standing behind the rest of the errors, and making some new ones.

But before examining the scientific accuracy of Neil's latest comments, given that his show is a political one, let's first talk about climate policy. On that subject, Neil explained why he focused on the so-called 'pause' in global surface warming during his show:

"it is legitimate to ask if the government takes the pause seriously and if it has any implications for policy ie, if there is a pause in warming, is there a case for the government to pause or slowdown its expensive efforts to decarbonise the economy until the picture becomes clearer?"

That certainly is a legitimate question. In fact, it's a question that a number of climate scientists have answered.

The question is based on the fact that a few recent studies have concluded that the sensitivity of the Earth's climate to the increased greenhouse effect may be slightly less than previous best estimates, based on the recent slowed surface warming (for a basic primer on climate sensitivity, see my previous entry here). There are reasons to be skeptical of this conclusion, but it's certainly a possibility. If true, would that mean governments should pause or slow down their efforts to decarbonize the economy, as Neil asks?

The authors of these studies (e.g. Myles Allen, Piers Forster, and Alexander Otto) all seem to agree, the answer is no.

In short, if these studies are right, it might take us an extra decade or so to reach global warming levels considered unacceptably dangerous. If true, that would certainly be welcome news. The problem is that from a policy perspective today, these sorts of details don't matter.

In order to avoid what's internationally considered dangerous levels of global warming, we need to achieve tremendous levels of greenhouse gas emissions reductions. Developed nations like the UK and USA will need to reduce their emissions by about 80 percent by the year 2050 to give us a good shot to avoid committing the planet to 2°C average surface warming, and even that is considered too risky by many climate scientists.

So if these studies are right, maybe we have until 2060 rather than 2050 to reduce our greenhouse gas emissions by 80 percent. If we were on track to meet that target by 2050, it would be valid to ask whether we should slow down our efforts a bit, but we're not on track. In fact it's going to take everything we've got to get close – see here for a discussion of the level of effort it will take to meet these emissions targets.

We should certainly fashion a climate policy that will maximize the economic benefit associated with reducing greenhouse gas emissions, and what that policy should look like is a valid debate in which all who would like to participate are more than welcome. However, there is no question as to whether we can 'slow down' our efforts – we simply cannot afford to, even in the best-case scenario.

This graph shows that even at the lowest range of climate sensitivity, future global warming will take us well beyond any temperature experienced during civilised human history. The blue line represents reconstructed temperature. The red line represents measured and projected global surface temperature. The red dots show the projected warming in the year 2100 for three different climate sensitivities (high sensitivity 4.5°C, most likely sensitivity 3°C, low sensitivity 1.5°C).

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The Economist Screws Up on the Draft IPCC AR5 Report and Climate Sensitivity

Posted on 19 July 2013 by dana1981 &

Earlier today, The Economist published a piece of irresponsible journalism regarding information in the draft Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5).  The Economist saved us some effort by explaining the problems with their own article:

“There are several caveats. The table comes from a draft version of the report, and could thus change. It was put together by the IPCC working group on mitigating climate change, rather than the group looking at physical sciences. It derives from a relatively simple model of the climate, rather than the big complex ones usually used by the IPCC. And the literature to back it up has not yet been published.”

So folks at The Economist, please explain to us, why are you reporting on climate sensitivity information in this draft report about climate mitigation that uses a simple climate model and is based on unpublished literature?

Readers may recall that climate contrarian blogs behaved in a similar fashion when the IPCC AR5 draft report on the physical science was “leaked” last December.  The contrarians made a huge to-do about a figure that seemed to show global surface temperature measurements at the very low end of the IPCC model projections.  As we discussed at the time, in reality the IPCC temperature projections have been very accurate.  As Tamino noted, the draft IPCC graph itself was flawed, using a single year as the baseline (1990) rather than aligning the data and models based on the existing trend in 1990.  Fast forward a few months later, and we hear from IPCC reviewers that this graph has been revised accordingly, now correctly reflecting the accuracy of the IPCC surface temperature projections.  The lesson to be learned is that you shouldn’t report on draft documents that are subject to change!

Thus problem #1 is that this article never should have been written, and doing so was a great example of irresponsible journalism, as climate scientist Kevin Trenberth told Climate Progress.  Problem #2 is that The Economist’s interpretation of the information from the draft IPCC report is wrong.  A similar table is shown in the 2007 IPCC Fourth Assessment Report (AR4) (Table SPM.5):

Table SPM.5 

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Debunking New Myths about the 97% Expert Consensus on Human-Caused Global Warming

Posted on 17 July 2013 by dana1981 &

This post has been incorporated into the rebuttal to the myth "97% consensus on human-caused global warming has been widely discredited and misclassified 35% of abstracts"

A survey of over 12,000 peer-reviewed climate science papers by our citizen science team at Skeptical Science found a 97% consensus among papers taking a position on the cause of global warming in the peer-reviewed literature that humans are responsible.  Not surprisingly, our results have been subject to attacks from those who would prefer to continue to deny the reality of the expert consensus on human-caused global warming.

For example, on Sunday July 14th, 2013, Andrew Neil hosted UK Energy and Climate Change Secretary Ed Davey on the BBC show Sunday Politics.  Rather than discussing politics, Neil began the show by misrepresenting our consensus paper, making several false statements about it within the first 2 minutes of the show.

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Patrick Michaels: Cato's Climate Expert Has History Of Getting It Wrong

Posted on 13 July 2013 by dana1981 &

This is a re-post of a devastating debunking of Patrick Michaels' history of wrong climate predictions by Shauna Theel at Media Matters.

A review of claims made by the Cato Institute's Patrick Michaels over the last quarter century shows that he has repeatedly been proven wrong over time. Michaels is one of a few contrarian climate scientists who is often featured in the media without disclosure of his funding from the fossil fuel industry.

Patrick Michaels' Losing Bets

On Temperature Trends

Michaels "Bet" In 1999 There Would Be A "Statistically Significant Cooling Trend" From 1998 To 2008.  In a Cato post that was later published as a Washington Times op-ed, according to Nexis, Patrick J. Michaels wrote that he would place a "bet" that "the 10 years ending on December 31, 2007, will show a statistically significant global cooling trend in temperatures measured by satellite":

I'm willing to wager two things. First, I'll bet that anyone who said global warming is an overblown bunch of hooey had a terrible time at this year's holiday cocktail parties. Second, I'll take even money that the 10 years ending on December 31, 2007, will show a statistically significant global cooling trend in temperatures measured by satellite.

[...]

Last year was so warm that it induces a statistically significant warming trend in the satellite data. Thus the second bet: Starting with 1998, there will almost certainly be a statistically significant cooling trend in the decade ending in 2007. [Cato, 1/18/99]

Satellite Records For That Decade Showed No Statistically Significant Trend. From 1998 to 2008, the University of Alabama in Huntsville satellite record shows a warming trend that is not statistically significant at the 95 percent level (a warming of 0.074°C per decade plus or minus 0.439°C). The Remote Sensing Systems satellite record shows a cooling trend that is not statistically significant at the 95 percent level (a change in temperature of -0.053°C per decade plus or minus 0.425 °C). The three surface temperature records showed a "warming trend" for that time period according to a Skeptical Science report on a 2008 paper by the Australian Bureau of Meteorology. [Calculated using Skeptical Science's Temperature trend calculator, 7/1/13] [Skeptical Science, 1/10/13]

Michaels' New Bet: "We Are Going To Go Nearly A Quarter Of A Century Without Warming." In a Washington Times op-ed in January 2013, Michaels stated "it's a pretty good bet that we are going to go nearly a quarter of a century without warming." [The Washington Times, 1/17/13]

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Charles Krauthammer's flat-earther global warming folly

Posted on 10 July 2013 by dana1981 &

Fox News commentator Charles Krauthammer recently wrote an opinion piece that was published by many media outlets including The Washington Post, claiming that President Obama's Climate Action Plan is a "folly." In fact, the real follies lie in Krauthammer's arguments.

Krauthammer's article begins in a schizophrenic manner, claiming that "Global temperatures have been flat for 16 years — a curious time to unveil" a climate action plan, but then admitting that this "doesn't mean there is no global warming." Indeed it does not. In fact, over the past 16 years, the planet has accumulated an amount of heat equivalent to about 2 billion Hiroshima atomic bomb detonations. Krauthammer objects to the President's comment that "We don't have time for a meeting of the Flat Earth Society," because we don't understand everything about the Earth's climate, like exactly why surface temperatures have warmed relatively slowly over the past 16 years (though we do have a good idea).

Of course, the choice of the 16-year window is a juicy cherry pick. It puts the starting point right at the formation of the 1997–1998 El Niño, one of the strongest in the past century. During El Niño events, heat is transferred from the oceans to the air, causing abnormally hot surface temperatures. Focusing on the slow surface air warming over the past 16 years is like arguing that your car is broken because it slowed down as you approached a stop sign. Krauthammer is focusing on an unrepresentative period during which the overall warming of the planet continued, but less heat was used in warming the air, and more in warming the ocean. However, climate research suggests that this is just a temporary change, and surface air warming will soon accelerate again.

Krauthammer also complains that "flat-earthers like Obama" have blamed heat waves on human-caused global warming. Indeed, recent research has shown that Australian heat waves and record-breaking monthly temperature records in general are now five times more likely to occur due to global warming, with much more to come. Papers have concluded that several individual heat records, like those in Texas and Oklahoma in 2011 and Moscow in 2010, would not have been broken if not for human-caused global warming. The video below from NASA shows how the distribution of summer temperatures has shifted towards hotter values over the past 60 years, making these heat records more likely to occur.

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The Consensus Project Update and Dana on Al Jazeera Inside Story

Posted on 6 July 2013 by & dana1981

Cook et al. (2013) has now been downloaded over 64,000 times, becoming the most-downloaded paper ever published by Environmental Research Letters.  During the speech announcing his new Climate Action Plan, President Obama again mentioned the 97% expert consensus on human-caused global warming. 

Awareness of the 97% consensus figure has spread far and wide.  To help close the consensus gap, check out sks.to/consensuspics and make use of the consensus graphics.

I also discussed President Obama's climate plan along with Daniel Kessler from 350.org on Al Jazeera Inside Story.

I was also on Inside Story once previously to discuss The Consensus Project.

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8 comments


4 Hiroshima bombs worth of heat per second

Posted on 1 July 2013 by John Cook & dana1981

UPDATE 27 Mar 2014: I just discovered that my talk at the Climate Action Summit was posted on YouTube:

Last weekend, I gave a talk at the Climate Action Summit on the latest climate science. During the talk, I showed the following graph of the Earth's total heat content, demonstrating that even over the last decade when surface temperature warming has slowed somewhat, the planet continues to build up heat at a rate of 4 Hiroshima bomb detonations worth of heat every second. This data comes from a paper lead authored by Australian climate scientist John Church that tallies up the heat accumulating in the oceans, warming the land and atmosphere and melting the ice:

The next day, I was (pleasantly) surprised to see an AAP journalist had written an article about my talk (and also included some of the science on extreme weather presented by the distinguished scientist Lesley Hughes who spoke after me). The headline, "Climate change like atom bomb", focused on the Hiroshima metaphor (which I believe was first used several years ago by James Hansen). The article was picked up by a number of outlets across the world with a curious concentration of coverage in India. Subsequently, a number of people have commented on this metaphor or emailed me questions. So I thought I would address in this post, with some help from Dana Nuccitelli, why we use this metaphor and how the "4 Hiroshima bombs worth of heat per second" was calculated.

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47 comments


Agnotology, Climastrology, and Replicability Examined in a New Study

Posted on 28 June 2013 by dana1981 &

A new paper is currently undergoing open public review in Earth System Dynamics (ESD) titled Agnotology: learning from mistakes by Benestad and Hygen of The Norwegian Meteorological Institute, van Dorland of The Royal Netherlands Meteorological Institute, and Cook and Nuccitelli of Skeptical Science.  ESD has a review system in which anybody can review a paper and submit comments to be considered before its final publication.  So far we have received many comments, including from several authors whose papers we critique in our study, like Ross McKitrick, Craig Loehle, and Jan-Erik Solheim.  We appreciate and welcome all constructive comments; the discussion period ends on July 4th.

Agnotology is the study of how and why we do not know things, and often deals with the publication of inaccurate or misleading scientific data.  From this perspective, we attempted to replicate and analyze the methods and results of a number of climate science publications. 

We focused on two papers claiming that factors other than human greenhouse gas emissions are responsible for the global warming observed over the past century – specifically, the orbital cycles of various planetary bodies in the solar system.  Since there is no physical reason to believe that the orbits of other planets should have any significant effect on the Earth's climate, and these papers generally do not propose a physical mechanism behind this supposed influence, this hypothesis is often referred to as "climastrology," because it's essentially an application of astrology to climate change.

In our study, we attempted to replicate the methods and results in these and a number of other papers to evaluate their validity.  In the process, we found many different types of errors that can appear in any paper, but that appear to be common to those which purport to overturn mainstream climate science.

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19 comments


President Obama acts on climate change by enforcing the law

Posted on 25 June 2013 by dana1981 &

This is a re-post from The Guardian's Climate Consensus – the 97%.

Obama Gives Major Speech On Climate Change
Barack Obama speaks as he unveils his plan on climate change at Georgetown University in Washington DC. Photograph: Alex Wong/Getty Images

In his state of the union speech this February, President Obama vowed,

If Congress won't act soon to protect future generations, I will. I will direct my cabinet to come up with executive actions we can take, now and in the future, to reduce pollution, prepare our communities for the consequences of climate change, and speed the transition to more sustainable sources of energy.

President Obama followed through on that promise today, unveiling a climate action plan that includes measures to reduce greenhouse gas emissions, accelerate renewable energy permitting on public lands, and prepare American infrastructure for the impacts of climate change.

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44 comments


Media Overlooking 90% of Global Warming

Posted on 25 June 2013 by dana1981 &

As we have previously discussed, the overall warming or heat accumulation of the planet has continued, and if anything accelerated over the past 10–15 years (Figure 1).

Fig 1

Figure 1: Land, atmosphere, and ice heating (red), 0-700 meter OHC increase (light blue), 700-2,000 meter OHC increase (dark blue).  From Nuccitelli et al. (2012).

Misleading 'Pause' Articles

However, over the past week or two there has been a spate of articles from the New York Times, Washington Post, The New Republic, and Der Spiegel, all of which get many details right (including noting the warming of the oceans), but that all begin from the premise that “global warming” has slowed. 

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37 comments


Is More Global Warming Hiding in the Oceans?

Posted on 22 June 2013 by dana1981 &

This is a re-post of an article in US News & World Report by Jeff Nesbit

The HMS Challenger set sail 135 years ago. It was the world's first scientific survey of ocean life. But the HMS Challenger also studied ocean temperatures along the way by dropping thermometers attached to Italian hemp ropes hundreds of meters deep – an effort that has been used as a baseline for global warming in oceans since pre-industrial times.

Now, according to a new study, U.S. and Australian researchers have combined the work of the HMS Challenger with modern-era climate science models – and have some surprising results. The study found we may be significantly under-estimating global warming's impact and heat content in the oceans; and sea level rise from global warming seems to be split 60/40, with 40 percent coming from expansion of sea water caused by warming, and the remaining 60 percent coming from melting ice sheets and glaciers.

The U.S. and Australian researchers who re-examined the HMS Challenger thermometer readings in light of modern supercomputer climate models say it provides further confirmation of human-produced global warming over the past century.

"Our research revealed warming of the planet can be clearly detected since 1873 and that our oceans continue to absorb the great majority of this heat," said Dr. Will Hobbs, the study's lead author and a researcher at the University of Tasmania's Institute for Marine and Antarctic Studies. "Currently scientists estimate the oceans absorb more than 90 percent of the heat trapped by greenhouse gases, and we attribute the global warming to anthropogenic causes."

The HMS Challenger expedition ran from 1872 to 1876, and was the world's first global scientific survey of life beneath the ocean surface. But, while it wasn't part of its central research mission, the Challenger also dropped thermometers deep into the ocean at different points. More than a century later, researchers used state-of-the-art climate models to get a more accurate picture of how the world's oceans have changed since the Challenger's voyage.

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Citizens Climate Lobby - Pushing for a US Carbon Fee and Dividend

Posted on 18 June 2013 by dana1981 &

Citizens Climate Lobby (CCL) is a group that formed in order to organize and empower citizens to push for a carbon fee and dividend – the preferred solution of former NASA climate scientist James Hansen.

The Importance of Carbon Pricing

Putting a price on carbon emissions is a key climate solution.  Failing to price carbon emissions is effectively a massive subsidy, estimated at about $800 billion per year globally by the International Monetary Fund.  However, that estimate was based on a carbon damages cost that was recently revised upwards by about 50% by the US government, based on up-to-date economic modeling.  Using conservative assumptions, global subsidies for the climate costs of carbon emissions now exceed $1.1 trillion per year, and may be much higher.

The absence of a carbon price to account for those costs is a failure of the free market.  It prevents citizens from making informed purchasing decisions, because the actual costs of the products they buy are not accurately reflected in their market prices.  When it comes to climate costs, American and Canadian consumers are flying blind.  Unfortunately we can't avoid paying the costs of climate damage forever, and they are reflected in effects like rising food prices when crops are decimated by extreme weather like heat waves and droughts, with contributions from human-caused climate change.

Why Fee and Dividend?

Personally as long as we implement a carbon price, I don't have a strong preference about what form it takes.  There are a number of options, with cap and trade and carbon taxes being the most commonly implemented.  Once a carbon price is put in place, there is also the question what to do with the generated funds.  Some prefer that they be used to fund low carbon technologies to help solve the climate problem, while others would prefer they be used to balance government budgets, and others prefer that they be returned directly to citizens as a 100% dividend.

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Heartland's Chinese Academy of Sciences Fantasy

Posted on 14 June 2013 by dana1981 &

Update: the Chinese Academy of Sciences has released a statement about Heartland's "misleading statement".  See below for details.

As Cook et al. 2013 (also known as The Consensus Project) showed, the consensus in the peer-reviewed scientific literature that humans are causing global warming has been growing over the past two decades.  In 2011, 98% of papers taking a position on the cause of global warming agreed that humans are causing it.

consensus growth

Percentage of "global warming" or "global climate change" papers endorsing the consensus among only papers that express a position endorsing or rejecting the consensus.  From Cook et al. (2013).

However, as Graham Readfearn recently documented, over those same two decades, fossil fuel interests have engaged in a number of campaigns to cast doubt on the existence of the consensus on human-caused global warming.  Convincing the public that this settled science is still in dispute has long been a top priority for industry groups.

consensus vs. denial

The results of Cook et al. 2013 juxtaposed with some fossil fuel-funded campaigns to deny the scientific consensus.  Image by jg.

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38 comments


Meet the world's best new environment bloggers

Posted on 7 June 2013 by dana1981 &

Miss the New York Times environment blogs and reporting?  Then check out the new Guardian environment blogs whose new page is being officially unveiled today.  Also check out my Climate Consensus – the 97% blog post for today, More pieces of the global warming puzzle assembled by recent research.

Meet the world's best new environment bloggers


Lake Baikal, Siberia photographed by Chris Hadfield on the International Space Station
Lake Baikal, Siberia, photographed by Chris Hadfield on the International Space Station. We don't have a blogger in orbit yet, but watch this space. Photograph: Chris Hadfield/NASA

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Lu Blames Global Warming on CFCs (Curve Fitting Correlations)

Posted on 5 June 2013 by dana1981 &

A paper just published in an obscure physics journal by the University of Waterloo's Qing-Bin Lu (2013) has drawn quite a bit of media attention for blaming global warming not on carbon dioxide, but rather on chlorofluorocarbons (CFCs, which are also greenhouse gases).  However, there are numerous fundamental flaws in the paper, which is based almost entirely on correlation (not causation) and curve fitting exercises.

Lu's hypothesis can be disproven very simply.  He argues that the radiative forcing (global energy imbalance) from CFCs matches global surface temperatures better than that from CO2 over the past decade.  This is because as a result of the Montreal Protocol, CFC emissions (and emissions of other halocarbons) have been flat over the past decade, and global surface air temperatures have also been essentially flat during that short timeframe, while CO2 emissions have continued to rise.

However, a global energy imbalance doesn't just impact surface temperatures.  In fact, only about 2% of global warming is used in heating the atmosphere, while about 90% heats the oceans.  Over the past decade, ocean and overall global heating have continued to rise rapidly, accumulating the equivalent of about 4 Hiroshima atomic bomb detonations per second (Figure 1).

Fig 1

Figure 1: Land, atmosphere, and ice heating (red), 0-700 meter OHC increase (light blue), 700-2,000 meter OHC increase (dark blue).  From Nuccitelli et al. (2012).

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Imbers et al. Test Human-Caused Global Warming Detection

Posted on 3 June 2013 by dana1981 &

A new study published in the Journal of Geophysical Research – Atmospheres by Imbers, Lopez, Huntingford, and Allen tests the robustness of the detection of human-caused global warming in previous studies.  Specifically their study builds on Lean and Rind (2009), Folland et al. (2013) (which they refer to as Folland 2011, based on an abstract presented at the AGU conference in 2011 of the recently-published 2013 paper), Kaufmann et al. (2011), and Lockwood (2008), as well as considering Loehle and Scafetta (2011).

Imbers et al. investigated whether using different characterizations and models of internal natural variability in the climate system (for example the El Niño Southern Oscillation [ENSO] and Atlantic Multidecadal Oscillation [AMO]), with both short and long memory processes, would impact the detection of the human-caused global warming signal.  The results of the previous studies listed above are illustrated in Figure 1.

Imbrie Fig 1

Figure 1: The top panel shows the observed global mean air surface temperature anomaly from HadCRUT3 (gray line) and the best multivariate fits using the methods of Lean and Rind [2009] (blue line), Lockwood [2008] (red line), Folland et al. [2011] (green line), and Kaufmann et al. [2011] (orange line). The remaining panels show the individual temperature contributions to the top panel fits from ENSO (second panel), volcanoes (third panel), solar irradiance (fourth panel), anthropogenic contribution (fifth panel), and other factors (sixth panel) that include the AMO for Folland et al. [2011] and minor annual, semi-annual, and 17.5 year cycle identified by Kopp and Lean [2011] in the residuals of Lean and Rind’s [2009] model.

The human contribution to global surface warming (the fifth panel in Figure 1) is shown in Figure 2.  Click the image for a larger version.

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48 comments


New Climate Magazine Launched - ClimateState

Posted on 2 June 2013 by dana1981 &

Chris Machens has launched a new online climate magazine and video site called ClimateState.  The first issue of the magazine features several Skeptical Science resources, including Dana's post on recent hurricane research, and The Consensus Project.

Check it out.

Climate State Issue 1

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0 comments


The 5 characteristics of global warming consensus denial

Posted on 28 May 2013 by John Cook & dana1981

All movements that reject an overwhelming scientific consensus show 5 inevitable characteristics. They celebrate fake experts, cherry pick the data, argue using misrepresentation and logical fallacies, indulge in conspiracy theories, and demand impossible expectations of what research can deliver.

These characteristics are seen in the movements that deny the scientific consensus on vaccination, HIV and AIDS and the link between smoking and cancer. They are also abundantly evident in the movement that denies the scientific consensus that humans are causing global warming.

Industry and conservative groups have been attacking scientific consensus for decades. As far back as 1991, Western Fuels Association launched a $510,000 campaign to "reposition global warming as theory (not fact)" in the public perception. A memo from communications strategist Frank Luntz leaked in 2002 advised Republican politicians to "continue to make the lack of scientific certainty a primary issue in the debate." In a recent analysis of syndicated conservative opinion pieces spanning 2007 to 2010, the most popular myth was “there is no consensus”.

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81 comments


Matt Ridley's misguided climate change policy

Posted on 23 May 2013 by dana1981 &

This is a re-post from The Guardian's Climate Consensus – the 97%

In an opinion article for the London Times this past Monday, writer Matt Ridley discussed his interpretation of a new paper which suggests that the Earth's climate sensitivity may be a bit lower than current best estimates. Climate sensitivity refers to the average amount of warming that will occur at the Earth's surface in response to an increased greenhouse effect.

This new paper, led by Alexander Otto at the University of Oxford, suggested that the Earth's surface may warm a bit more slowly than climate models generally indicate. I roughly estimate that about 80% of the warming over the past century would be due to human carbon dioxide emissions, if the results of this study are correct. The good news is that Ridley has accepted the consensus amongst 97% of climate experts that humans are causing global warming and has moved on to examine the consequences.

One of the paper's authors, Myles Allen noted in The Guardian that the results of the study would make little difference with respect to long-term climate change.

"...our new findings mean that the changes we had previously expected between now and 2050 might take until 2065 to materialise instead."

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Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature

Posted on 16 May 2013 by dana1981 & John Cook

A new survey of over 12,000 peer-reviewed climate science papers by our citizen science team at Skeptical Science has found a 97% consensus among papers taking a position on the cause of global warming in the peer-reviewed literature that humans are responsible.

consensus pie chart

Lead author John Cook created a short video abstract summarizing the study:

The Abstracts Survey

The first step of our approach involved expanding the original survey of the peer-reviewed scientific literature in Oreskes (2004).  We performed a keyword search of peer-reviewed scientific journal publications (in the ISI Web of Science) for the terms 'global warming' and 'global climate change' between the years 1991 and 2011, which returned over 12,000 papers.

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306 comments


Another Piece of the Global Warming Puzzle - More Efficient Ocean Heat Uptake

Posted on 13 May 2013 by dana1981 &

Although it is still within the range of model simulations, the rate of global surface air warming over the past decade has slowed.  Climate scientists, being scientists, would like to explain exactly why that has happened. 

There are several possible explanations.  Perhaps it's due to the natural internal variability (short-term noise) in the climate system, with more heat being shifted to the deeper oceans as a result of more recent La Niña events.  Perhaps it's due to a smaller global energy imbalance due to more aerosol cooling and lower solar activity offsetting more of the greenhouse gas-caused warming.  Perhaps it's a combination of several factors, but which is the main cause of the slowed surface warming over the past decade?

Meehl et al. (2011) found that in their model simulations, there were 'hiatus decades' with little surface warming, but increased deep ocean warming (Figure 1).  Similarly, Guemas et al. (2013) concluded that most of the recent slowed surface warming can be attributed to the increased accumulation of heat in the oceans.

 

Figure 1: Composite global linear trends for hiatus decades (red bars) and other decades (green bars). Positive values for top of the atmosphere (TOA) net radiation (left-hand side) indicate energy accumulating in the system (i.e. global warming). Right-hand side shows ocean heat content decadal trends, for the various ocean layers.  From Meehl et al. (2011).

These results are also consistent with several studies showing a recent increase in ocean warming (e.g. Levitus et al. 2012, Nuccitelli et al. 2012, and Balmaseda et al. 2013). 

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The evidence for climate change WITHOUT computer models or the IPCC

Posted on 11 May 2013 by dana1981 &

This is Peter Hadfield's (potholer's) latest climate video, summarizing the evidence for human-caused climate change, excluding climate models and the IPCC.

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26 comments


What you need to know about climate sensitivity

Posted on 10 May 2013 by dana1981 &

This is a partial re-post of my latest in the Guardian's Climate Consensus – the 97%.  It's intended as a basic primer to reference the next time somebody tells you global warming is nothing to worry about because climate sensitivity is low.

What you need to know about climate sensitivity

geoengineering : SPICE , Stratospheric Particle Injection for Climate Engineering : clouds and sun
Clouds are the only plausible feedback that could significantly dampen future global warming. Photograph: Graham Turner for the Guardian

Climate sensitivity is a subject sometimes explored in mainstream media articles. For example, The Economist tried to summarize some recent research on the subject, although as climate scientist Michael Mann and I noted in an article for ABC, they made some key mistakes.

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Distinguishing Between Short-Term Variability and Long-Term Trends

Posted on 6 May 2013 by dana1981 &

We previously examined a paper published by McLean, de Freitas, and Carter (2009) which showed that most of the short-term variability in lower atmosphere temperatures is due to changes in the El Niño Southern Oscilliation (ENSO).  This was not a new finding at the time, but the authors also subsequently claimed that changes in ENSO could explain a substantial amount of the long-term global warming trend.  This claim was not supported by the analysis in their paper.

Nevertheless, lead author John McLean predicted a record-shattering cooling for the year 2011, based on the methodology in their paper.  As we subsequently documented, that prediction was quite far off (Figure 1).

McLean failure

Figure 1: NCDC global average surface temperature from 1880 through 2010 (blue), McLean's 2011 prediction (orange), and the actual 2011 NCDC temperature (purple).

Average global surface temperatures were cooler in 2011 than 2010 mainly as a result of changes in ENSO.  We know that La Niña years tend to be colder at the Earth's surface while El Niño years tend to be hotter (Figure 2).

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9 comments


Roy Spencer's Catholic Online Climate Myths

Posted on 1 May 2013 by dana1981 &

Roy Spencer was recently interviewed by the website Catholic Online, and unfortunately spent most of the interview repeating long-debunked climate myths.  He could have simply answered the questions with factually correct information, and expressed his climate 'skepticism' where appropriate.  Had he taken this approach, the Catholic Online readers could have become better informed on the subject of climate change, as well as potentially seeing where Roy Spencer's 'skepticism' comes from.

Instead, Roy Spencer responded to most of the questions with factually wrong answers.  It was the sort of interview you might expect from a climate contrarian blogger like Anthony Watts, but you would hope that a climate scientist could do much, much better.  Unfortunately, Spencer disappointed.  Here we will compare Spencer's assertions to the body of scientific evidence and see where he went wrong.

Global Warming is Happening

Spencer began the interview by trying to cast doubt on the existence of global warming.

"No one knows whether it is currently warming, because we only see warming "in the rearview mirror"...after it has occurred."

To his credit, Spencer did mention that "there is some evidence that the deep ocean has continued to warm."  However, we absolutely do know that the planet is currently warming.  Aside from the fact that we measure that warming directly, we also know that there is a global energy imbalance due to the fact that humans have increased the greenhouse effect.  Physically, we know that the planet will continue to warm as long as we continue to increase the greenhouse effect.

Arctic Sea Ice Decline Denial

Spencer next repeated a variant of a myth we previously examined from his University of Alabama at Huntsville colleague, John Christy.

"It is entirely possible that summer sea ice meltback now is no worse than it was back in the 1920's and 1930's, when ship explorers reported unprecedented warming and sea ice and glacier changes in the Arctic"

While we didn't have satellites monitoring Arctic sea ice in the 1920s or 1930s or 1940s, all available data indicate that Arctic sea ice was much, much more extensive during that timeframe than today.  One of the most widely used long-term estimates of Arctic sea ice extent comes from Walsh and Chapman (2001), whose data are available from the University of Illinois (updated through 2008).  A description of the vast array of data used by Walsh and Chapman is available here, and the data are plotted in Figure 1.

summer sea ice extent

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New Research Shows Humans Causing More Strong Hurricanes

Posted on 29 April 2013 by dana1981 &

The link between human-caused global warming and extreme weather is often difficult to pin down, particularly with regards to hurricanes.  As Kevin Trenberth has discussed, all weather now occurs in a climate that humans have altered.

"it is important to recognize that we have a “new normal,” whereby the environment in which all storms form is simply different than it was just a few decades ago.  Global climate change has contributed to the higher sea surface and sub-surface ocean temperatures, a warmer and moister atmosphere above the ocean, higher water levels around the globe, and perhaps more precipitation in storms."

Two new papers have recently been published examining the link between global warming and hurricane intensity.  In both cases, the scientists have found evidence that the most intense hurricanes are already occurring more often as a result of human-caused global warming.  However, their predictions about future hurricane changes differ somewhat.

Grinsted on Hurricane Storm Surges

Last year, Tamino examined Grinsted et al. (2012), which demonstrated that the most extreme storm surge events can mainly be attributed to large landfalling hurricanes, and that those events are strongly linked to hurricane damage.  The study also found that there have been twice as many Katrina-magnitude storm surge events in globally warm years as compared to cold years.

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5 comments


Announcement: New Guardian Blog by Dana Nuccitelli and John Abraham

Posted on 24 April 2013 by dana1981 &

I'm very pleased (or chuffed, as they might say in the UK) to announce the launch of a new blog at The Guardian Environment.  This blog is a collaboration between myself (Dana Nuccitelli) and John Abraham.

banner

Back in December 2012, the Guardian announced that they would be establishing a page of environment blogs, following the successful example set by the Guardian Science Blogs.  This of course was a tremendous opportunity, as The Guardian is one of the world's premier newspapers, already with among the best environment and climate reporting.  As a result, they received over 800 applications and spent the next few months weeding through them to ultimately choose the top 1–2%.  I was fortunate to make that cut, and they gave several of us a bit of a tryout (here's mine and John Abraham's and Graham Readfearn's, for example).

Having previously collaborated and with similar styles, John Abraham and I offered to team up.  Our new blog is titled 'Climate Consensus – the 97%' (the inspiration for the name will be made clear in the near future).  My first post, on the subject of an uncharacteristically poor climate article by Reuters, can be read hereGraham Readfearn also has a pending new blog which I believe will be called 'Planet Oz', and it sounds like there will be several other very interesting new blogs and bloggers on the page soon.

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19 comments


Major PAGES 2k Network Paper Confirms the Hockey Stick

Posted on 22 April 2013 by dana1981 &

PAGES (Past Global Changes) is a scientific network which supports research aimed at understanding the Earth’s past environment in order to make predictions for the future.  It's funded by the U.S. and Swiss National Science Foundations, and the National Oceanic and Atmospheric Administration (NOAA).  Over 5,000 scientists from more than 100 countries subscribe to PAGES, which is essentially an organizational group to bring international scientists together.

In 2006, scientists in the PAGES network decided to organize an initiative to reconstruct the climate of the last 2,000 years, which they called The PAGES 2k Network.  This network consists of scientists from 9 regional working groups, each of which collects and processes the best paleoclimate (past climate change) data from their respective region.  It's a clever approach because it allows the experts in their local proxy data to contribute to a much larger global project.

The 2K Network has just published a major paper in Nature Geoscience (abstract and figures here), with 78 researchers contributing as co-authors from 60 separate scientific institutions around the world.  The analysis combines records from tree rings, pollen, corals, lake and marine sediments, ice cores, stalagmites and historical documents from 511 locations across seven continental-scale regions to reconstruct past global surface temperature changes over the past 2,000 years. 

Their two main results are a confirmation that current global surface temperatures are hotter than at any time in the past 1,400 years (the general 'hockey stick' shape, as shown in Figure 1), and that while the Medieval Warm Period (MWP) and Little Ice Age (LIA) are clearly visible events in their reconstruction, they were not globally synchronized events.

fig 4

Figure 1: a) Previously published Northern Hemisphere 30-year-mean temperature reconstructions relative to the 1961–1990 reference period. b) Standardized 30-year-mean temperatures averaged across all seven continental-scale regions. Blue symbols are area-weighted averages, and bars show 25th and 75th unweighted percentiles to illustrate the variability among regions; open black boxes are unweighted medians. The red line is the 30-year-average annual global temperature from the HadCRUT4 instrumental time series relative to 1961–1990, and scaled visually to match the standardized values over the instrumental period.

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11 comments


Climate Sensitivity Single Study Syndrome, Nic Lewis Edition

Posted on 18 April 2013 by dana1981 &

Nic Lewis has written a paper on the subject of the Earth's climate sensitivity (how much surface temperatures will warm in response to the increased greenhouse effect from a doubling of atmospheric CO2, including amplifying and dampening feedbacks) which has been accepted by the Journal of Climate.  First of all, we would like to offer kudos to Lewis for subjecting his analysis to the peer review process, which is something few climate contrarians are willing to do.

The paper is an outlier, finding a lower climate sensitivity than most other studies, and outside the likely range cited in the Intergovernmental Panel on Climate Change (IPCC) report.  It's most important not to fall into the trap of thinking that any single study will overturn a vast body of scientific evidence, derived from many different sources of data (or as Andrew Revkin calls this, single-study syndrome).  This was also recently an issue with regards to a similar and unpublished Norwegian study

Lewis' is just one paper using one of many possible methods to estimate climate sensitivity.  The overall body of evidence indicates that the Earth's surface temperatures will warm 2–4.5°C in response to a doubling of atmospheric CO2.

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45 comments


Guemas et al. Attribute Slowed Surface Warming to the Oceans

Posted on 15 April 2013 by dana1981 &

Recently we discussed a paper by Balmaseda et al., which found that the warming of the world's oceans has accelerated, and the heat accumulation in the oceans since 1999 is the most sustained warming period on record (over the past 50 years).  That unprecedented warming of oceans may help explain the slowed warming of surface temperatures over the past 10–15 years.

Another new paper published in Nature Climate Change by Guemas et al. (2013) specifically attempts to explain that recent slowed global surface warming.  The study concludes that most of the slowed surface warming can be attributed to the increased accumulation of heat in the oceans.

Data and Methods

The authors use the EC-Earth climate model and run an experiment in which the initial conditions are based on reconstructions of past climate changes.  Those reconstructions come from reanalysis data.  A reanalysis is a climate or weather model simulation of the past that incorporates data from historical observations.  For the ocean component, they use the same European Centre for Medium-Range Weather Forecasts' Ocean Reanalysis System 4 (ORAS4) as was used in the Balmaseda paper.  For the atmosphere and land component, they use the ERA40 and ERAinterim projects.

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21 comments


Further Comments on The Economist's Take on Climate Sensitivity

Posted on 11 April 2013 by dana1981 &

Last month, The Economist published an article about climate sensitivity – how much the planet's surface will warm in response to the increased greenhouse effect from a doubling of atmospheric CO2, including amplifying and dampening feedbacks.  We responded with some brief comments and critiques at the time.  Today two relevant and more in-depth articles on the subject were published, and are excerpted here.


How The Economist got it wrong

Dana Nuccitelli and Michael E Mann, ABC Environment, 12 Apr 2013

thermometer

The expected range of climate change is around 3 degrees. This is based on several lines of evidence and other factors.

A recent news article suggested that climate change may not be as bad as feared. But the report was based on one flawed study and missed a lot of important points.

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38 comments


Real Skepticism About the New Marcott 'Hockey Stick'

Posted on 10 April 2013 by dana1981 &

A new global temperature reconstruction over the past 11,300 years by Marcott et al. (2013) has been described as 'the new hockey stick,' and adopted into 'the wheelchair' by Jos Hagelaars by including temperatures further in the past and projected for the future (Figure 1).

Shakun_Marcott_HadCRUT4_A1B

Figure 1: The temperature reconstruction of Shakun et al (green – shifted manually by 0.25 degrees), of Marcott et al (blue), combined with the instrumental period data from HadCRUT4 (red) and the model average of IPCC projections for the A1B scenario up to 2100 (orange).

The Marcott paper has been subjected to an immense amount of scrutiny, particularly in the climate contrarian blogosphere, with criticisms about everything from the wording of its press release to the timing of its Frequently Asked Questions (FAQ) publication.  Unfortunately climate contrarians have been so noisy in their generally invalid criticisms that the media has begun to echo them, for example in this Washington Post blog.

With all the hubub, it's easy to lose sight of the important conclusions of this paper.  The bottom line is that the rate of warming over the past century is very rapid and probably unprecedented for the past 11,000 years.  That's actually both good and bad news.

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102 comments


Land Surface Warming Confirmed Independently Without Land Station Data

Posted on 8 April 2013 by dana1981 &

A new paper published in Geophysical Research Letters, Independent confirmation of global land warming without the use of station temperatures by Compo et al. (2013) takes a new approach at confirming the accuracy of the instrumental surface temperature record.

Their study seeks to bypass all criticisms of the thermometers themselves by creating a surface temperature record that does not include land thermometer station data.  The results are shown in Figure 1 with their surface land temperature reconstruction (dark blue) compared to that from the University of East Anglia Climatic Research Unit (CRU) (CRUTEM4, in red), and the average of five other instrumental surface temperature data sets in black.

Compo Fig 1

Figure 1: Temporal comparison of near-global land (90°N–60°S) 2 meter air temperature anomalies (TL2m) between 20CR and station-temperature based estimates. Red curve: global TL2m anomaly series from CRUTEM4, black curve: the average of five additional station-temperature datasets, and blue curve: the 20CR. 95% uncertainty ranges are shown for CRUTEM4 (yellow fill) and 20CR (blue fill) and their overlap (green fill).  From Compo et al. (2013)

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8 comments


The Fool's Gold of Current Climate

Posted on 4 April 2013 by dana1981 &

A frequent argument made by climate contrarians is that global warming hasn't yet resulted in unbearable climate change consequences, and therefore we have nothing to worry about.  In a talk recorded by ReasonTV, Matt Ridley offers up several different examples of this line of thinking, arguing that climate change thus far has had some positive consequences and that fossil fuels are just great, implying that we should continue to consume them without worry.

However, this argument misses a key point – climate scientists aren't terribly concerned about the current state of the Earth's climate.  If we were to stabilize atmospheric CO2 levels below 400 parts per million (ppm) – a level we are rapidly approaching – most people would be thrilled about that (especially if those levels eventually drop to somewhere around 350 ppm).  The concern is that human CO2 emissions and the resulting global warming show no signs of slowing (Figure 1).

RCP emissions

Figure 1: Estimated expected warming for the RCP scenarios in a most likely case world with 3°C equilibrium climate sensitivity (see this post for background and details).

The three higher warming scenarios in Figure 1 (red, green, and purple) describe the future that Ridley advocates for, where we see several more degrees of global surface warming over the next century.  That is the future we are concerned about.

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Trillions of Dollars are Pumped into our Fossil Fuel Addiction Every Year

Posted on 2 April 2013 by dana1981 &

A new report from the International Monetary Fund (IMF) estimates that overall global fossil fuel subsidies amount to about $1.9 trillion annually.  As large as this number sounds, it's actually an underestimate for many reasons.  The IMF report lists several of these reasons, including the fact that it's simply impossible to obtain data for all fossil fuel subsidies in all countries.  However, the biggest contributor to the conservative dollar figure is related to the social cost of carbon.

The social cost of carbon is an estimate of the direct effects of carbon emissions on the economy, and takes into consideration such factors as net agricultural productivity loss, human health effects, property damages from sea level rise, and changes in ecosystem services.  It's the economic damage caused by CO2 via climate change.  The IMF report uses an average US government agency value of $25 per tonne of CO2 emissions; however, there is substantial evidence and research suggesting the value should be much higher.  Dave Roberts provides some references in his post on the report, and we go into detail on the subject here.

The true cost of carbon emissions could easily be four times higher, at $100 per tonne.  Chris Hope, climate policy researcher at Cambridge University, has argued that an estimate around $150 per tonne may be more accurate.  Thus the true cost of our fossil fuel subsidies could be over $4 trillion per year, or over 6% of global Gross Domestic Product (GDP).  Compare that to the estimated cost of reducing greenhouse gas emissions to safe levels, which are generally on the order of 1% of GDP, and it becomes clear that our current priorities are completely backwards, pumping trillions of dollars into our fossil fuel addiction when we should be trying as hard as we can to break the habit.

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Making Sense of Sensitivity … and Keeping It in Perspective

Posted on 28 March 2013 by dana1981 &

Yesterday The Economist published an article about climate sensitivity – how much the planet's surface will warm in response to the increased greenhouse effect from a doubling of atmospheric CO2, including amplifying and dampening feedbacks.  For the most part the article was well-researched, with the exception of a few errors, like calling financier Nic Lewis "an independent climate scientist."  The main shortcomings in the article lie in its interpretation of the research that it presented.

For example, the article focused heavily on the slowed global surface warming over the past decade, and a few studies which, based on that slowed surface warming, have concluded that climate sensitivity is relatively low.  However, as we have discussed on Skeptical Science, those estimates do not include the accelerated warming of the deeper oceans over the past decade, and they appear to be overly sensitive to short-term natural variability.  The Economist article touched only briefly on the accelerated deep ocean warming, and oddly seemed to dismiss this data as "obscure."

The Economist article also referenced the circular Tung and Zhou (2013) paper we addressed here, and suggested that if equilibrium climate sensitivity is 2°C to a doubling of CO2, we might be better off adapting to rather than trying to mitigate climate change.  Unfortunately, as we discussed here, even a 2°C sensitivity would set us on a path for very dangerous climate change unless we take serious steps to reduce our greenhouse gas emissions.

Ultimately it was rather strange to see such a complex technical subject as climate sensitivity tackled in a business-related publication.  While The Economist made a good effort at the topic, their lack of expertise showed. 

For a more expert take on climate sensitivity, we re-post here an article published by Zeke Hausfather at the Yale Forum on Climate Change & the Media.

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New Research Confirms Global Warming Has Accelerated

Posted on 25 March 2013 by dana1981 &

A new study of ocean warming has just been published in Geophysical Research Letters by Balmaseda, Trenberth, and Källén (2013).  There are several important conclusions which can be drawn from this paper.

  • Completely contrary to the popular contrarian myth, global warming has accelerated, with more overall global warming in the past 15 years than the prior 15 years.  This is because about 90% of overall global warming goes into heating the oceans, and the oceans have been warming dramatically.
  • Some recent studies have concluded based on the slowed global surface warming over the past decade that the sensitivity of the climate to the increased greenhouse effect is somewhat lower than the IPCC best estimate.  Those studies are fundamentally flawed because they do not account for the warming of the deep oceans.
  • The slowed surface air warming over the past decade has lulled many people into a false and unwarranted sense of security.

The main results of the study are illustrated in its Figure 1.

BTKFig1

Figure 1: Ocean Heat Content from 0 to 300 meters (grey), 700 m (blue), and total depth (violet) from ORAS4, as represented by its 5 ensemble members. The time series show monthly anomalies smoothed with a 12-month running mean, with respect to the 1958–1965 base period. Hatching extends over the range of the ensemble members and hence the spread gives a measure of the uncertainty as represented by ORAS4 (which does not cover all sources of uncertainty). The vertical colored bars indicate a two year interval following the volcanic eruptions with a 6 month lead (owing to the 12-month running mean), and the 1997–98 El Niño event again with 6 months on either side. On lower right, the linear slope for a set of global heating rates (W/m2) is given.

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David Rose Hides the Rise in Global Warming

Posted on 19 March 2013 by dana1981 & John Russell

It seems like we have to debunk this myth on a weekly basis, as it keeps popping up in the mainstream media.  So, yet again, this is global warming:

Fig 1

Figure 1: Land, atmosphere, and ice heating (red), 0-700 meter ocean heat content (OHC) increase (light blue), 700-2,000 meter OHC increase (dark blue).  From Nuccitelli et al. (2012).

The overall warming of the Earth over the past 15 years was larger than over the previous 15 years.  Global warming has not stopped; it's not even slowed down.

A leading purveyor of the myth to the contrary is journalist David Rose, of the British tabloid The Mail on Sunday and Vanity Fair.  We've previously pre-bunked and debunked his articles on the subject, but he appears oblivious to any criticism of his work.

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New Study, Same Result - Greenhouse Gases Dominate Global Warming

Posted on 18 March 2013 by dana1981 &

A new study by Jones, Stott, and Christidis of the UK Met Office (Jones et al. 2013) examines the causes of global warming by using global climate model simulations from the World Climate Research Programme’s Coupled Model Intercomparison Project phase 5 (CMIP5) and comparing those model results to observed global surface temperatures.  CMIP5 is one of the largest collaborative efforts for bringing together climate model data for access by climate scientists across the world.  The prior phase, CMIP3 was used heavily in studies included in the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, while CMIP5 is used in many studies evaluated in the upcoming IPCC Fifth Assessment report, due out in 2013.

Over the past 60 years (1951–2010), the study finds that global average surface temperatures have warmed 0.6°C, while in climate models, greenhouse gases caused between 0.6 and 1.2°C surface warming.  This was offset by a cooling from other human influences (mainly from aerosols) of 0 to 0.5°C.  These results are consistent with all prior studies of the causes of global warming (Figure 1).

attribution 50 yr

Figure 1: Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WS12, dark green), and Jones et al. 2013 (J12, pink).

The climate model runs considering all external influences on global surface temperatures (mainly greenhouse gases, aerosols, the sun, and volcanic eruptions) simulate the observed temperature changes accurately (Figure 2).

Fig 4a

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Science vs. the Feelies

Posted on 17 March 2013 by dana1981 &

This is a re-post of Peter Hadfield's latest video.

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9 comments



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