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).
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).
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.
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.
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,
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.
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,
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.
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.
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.
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.
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.
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.
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.
Top frame: Global surface temperature anomalies. Bottom frame: Pacific wind stress anomalies. From England et al. (2014).
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:
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.
Posted on 4 February 2014 by dana1981 &
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,
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.
Posted on 29 January 2014 by dana1981 & Rob Painting
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.
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).
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.
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.
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."
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.
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.
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.
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.
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.
Posted on 25 December 2013 by dana1981 & John Cook
And from Santa Claus too.
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?
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.
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.
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.
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.
Posted on 2 December 2013 by dana1981 &
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.
Posted on 20 November 2013 by dana1981 &
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.
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.
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.
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).
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.
Posted on 22 October 2013 by dana1981 &
This is a re-post of an Ars Technica article by Scott K Johnson.
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.
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.
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.
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.
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.
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,
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.
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.
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.
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.
Posted on 18 September 2013 by dana1981 &
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:
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.
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 2004. Doran & 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.
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.
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.
Posted on 2 September 2013 by dana1981 &
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).”
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).
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).
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.
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.
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.'
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.
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.
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.
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.
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:
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),
Posted on 26 July 2013 by dana1981 &
This is a partial re-post from Texas Climate News
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:
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?
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.