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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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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.


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+.

Cook, J., Nuccitelli, D., Skuce, A., Way, R., Jacobs, P., Painting, R., Honeycutt, R., Green, S.A. (2014). Reply to Comment on ‘Quantifying the consensus on anthropogenic global warming in the scientific literature: a Reanalysis’. Energy Policy. DOI: 10.1016/j.enpol.2014.06.002

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. A., Abraham, J. P., Benestad, R. E., & Mandia, S. A. (2013). Comment on: Akasofu, S.-I. On the Present Halting of Global Warming. Climate 2013, 1, 4–11. Climate, 1(2), 76-83.

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.


Recent blog posts

Skeptical Science at the 2014 AGU Fall Meeting

Posted on 12 December 2014 by dana1981 &

A number of Skeptical Science contributors will be presenting at the 2014 AGU Fall Meeting.  If you'll be there, come check us out.

Time Presenter Type Location


Sunday, 14 December8:00 a.m. – 12:30 p.m. John Cook Workshop InterContinental Hotel, 888 Howard St, San Francisco

Communicating Climate Science Workshop

Deadline to apply is Fri., Oct. 31

Tuesday, 16 December 2014; 8:00 AM  Andy Skuce  Poster   

Abstract ID and Title: 7106: Emissions of Water and Carbon Dioxide from Fossil-Fuel Combustion Contribute Directly to Ocean Mass and Volume Increases

Final Paper Number: G21B-0444

Session Number and Title: G21B: Variability and Projection of Regional and Global Mean Sea Level Change I Posters

 Tuesday, 16 December 2014; 2:28 PM - 2:40 PM Dana Nuccitelli  Oral  Marriott Marquis; Salon 13-15

Abstract ID: 2476

Abstract Title: How to maximize science communication efficacy by combining old and new media

Final Paper Number: PA23B-04

Session Number and Title: PA23B: We Need to Talk: Learning from Climate Experts Who Have Succeeded in the Media

Wednesday, 17 December 2014; 8:00 AM - 10:00 AM  Peter Jacobs Oral  Moscone South; 102 

Abstract ID: 11019

Abstract Title: It Ain't (Just) the Heat, It's the Humanity: Increasing Public Understanding of Scientific Consensus and Its Role in Climate Literacy

Final Paper Number: ED31H-07

Presentation Length9:30 AM - 9:45 AM

Session Number and Title: ED31H: Climate Literacy: Culture of Science AND Broader Impacts Done Well I 

Wednesday, 17 December 2014: 10:20 AM - 12:20 PM John Cook Oral MS, 102

MS, 102
Applying Agnotology-Based Learning in a Mooc to Counter Climate Misconceptions

Wednesday, 17 December 2014; 1:40 PM John Mashey Poster  Moscone South; Poster Hall

Abstract ID and Title: 2428: The Machinery Of Climate Anti-Science, Its Efforts Against Education, Top To Bottom

Final Paper Number: ED33B-3513

Session Number and Title: ED33B: Climate Literacy: Overcoming Barriers—Research Outcomes and Best Practices for Supporting Education and Informed Decision Making II Posters

Wednesday, 17 December 2014; 5:30 PM - 5:45 PM Julian Brimelow Oral Moscone West; 3010 Abstract Title: Hydroclimatological Aspects of the Extreme 2011 Assiniboine River Basin Flood

Final Paper Number: H34C-07

Session Number and Title: H34C: Global Floods: Forecasting, Monitoring, Risk Assessment, and Socioeconomic Response II
Thursday, 18 December 2014: 01:40 PM - 03:40 PM John Cook Oral MW, 3004

Scientists Are from Mars, Laypeople Are from Venus: An Evidence-Based Approach to Consensus Messaging

Thursday, 18 December 2014; 3:00 PM - 3:20 PM Kevin Cowtan Oral   Moscone West; 3003

Abstract ID: 3409

Abstract Title: Biases in the instrumental temperature record: the policy and communications context

Final Paper Number: GC43G-05

Session Number and Title: GC43G: Quantifying Uncertainty in Climate, Earth System, Integrated Assessment, and Impact Models and Observations II



California just had its worst drought in over 1200 years, as temperatures and risks rise

Posted on 8 December 2014 by dana1981 &

A new paper published in the journal Geophysical Research Letters by Griffin & Anchukaitis concludes that the 2012–2014 drought in California was its most intense in at least 1,200 years.

The study used drought reconstructions from tree-ring cores, from the North American Drought Atlas (NADA) and from cores Griffin & Anchukaitis collected from blue oak trees in southern and central California. Blue oak tree ring widths are particularly sensitive to moisture changes. According to Griffin,

California’s old blue oaks are as close to nature’s rain gauges as we get

Pencil-like tree-ring cores are collected non-destructively using a Swedish increment borer. May 2014, image by Daniel Griffin. Pencil-like tree-ring cores are collected non-destructively using a Swedish increment borer. May 2014, image by Daniel Griffin.

The study compared today’s drought conditions in California to those reconstructed over the past 1,200 years using the Palmer Drought Severity Index (PDSI), an estimate of available soil moisture. The data showed that California is experiencing its most intense drought in over a millennium,



Volcanoes may be responsible for most of the global surface warming slowdown

Posted on 3 December 2014 by dana1981 &

A new study has found that when particulates from small volcanic eruptions are properly accounted for, volcanoes may be responsible for much of the slowdown in global surface warming over the past 15 years.

Sulfur aerosol particulates pumped into the atmosphere from volcanic eruptions cause short-term cooling by blocking sunlight. Until recently, climate scientists thought that only large volcanic eruptions had a significant impact on global temperatures. There haven’t been any big eruptions since Mount Pinatubo in 1991. However, studies published over the past few years have found that even moderate volcanic eruptions can pump significant amounts of aerosol particulates into the atmosphere.

Virtually all research into the climate influence of volcanic aerosols has used satellite measurements of particulates in the upper atmosphere (the stratosphere). These satellite measurements only monitor the volcanic aerosol at heights of 15 km and above. The new paper by David Ridley and colleagues studied the amount of volcanic aerosols in portions of the stratosphere that lie below 15 km.

To do this, the researchers combined data from satellites, ground-based instruments in the AERONET program, and from instruments on weather balloons. The study was co-authored by 17 climate scientists, including some leading experts in aerosol research.

By combining all of these measurements, the scientists found that there is also a significant amount of volcanic aerosol in portions of the stratosphere below 15 km They concluded that for recent eruptions, between 30 and 70% of the overall amount of volcanic aerosol in the stratosphere has come from below 15 km. Since the year 2000, the study estimates that volcanoes have had a cooling influence on global surface temperatures. The likely range of this volcanic cooling influence lies between 0.05 and 0.12°C.

As the authors of the paper note, this cooling influence is not taken into account in the climate model simulations incorporated into the latest IPCC report,

The climate model simulations evaluated in the IPCC fifth assessment report [Stocker et al., 2013] generally assumed zero stratospheric aerosol after about 2000, and hence neglect any cooling effect of recent volcanoes

Although the global surface temperature data have been within the range of model simulations, they’ve been towards the lower end of those model runs over the past 10–15 years.

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).



The latest global warming bill and the Republican conundrum

Posted on 25 November 2014 by dana1981 &

Senators Sheldon Whitehouse (D-RI) and Brian Schatz (D-HI) introduced a climate bill in the US Senate last week. The American Opportunity Carbon Fee Act proposes to tax carbon pollution at the source or at the border for imports, and return 100% of the revenue to taxpayers. The tax would therefore be revenue-neutral, not increasing the size of government.

A revenue-neutral carbon tax has become an increasingly popular proposal for tackling global warming. Liberals have long been on board with requiring that polluters pay for their carbon emissions, but in the United States and a few other countries where climate science is treated as a partisan issue, conservatives have been resistant to this concept.

Research has shown that fear of government regulations is one of the primary reasons conservatives tend to reject the overwhelming scientific evidence for human-caused global warming. A majority of Republicans accept the scientific reality when they realize there are free market solutions available.

From Campbell and Kay, “Solution Aversion: On the Relation between Ideology and Motivated Disbelief,” Journal of Personality and Social Psychology, 2014, Vol. 107, No. 5, 809–824. Published by the American Psychological Association, reprinted with permission.

From Campbell and Kay, “Solution Aversion: On the Relation between Ideology and Motivated Disbelief,” Journal of Personality and Social Psychology, 2014, Vol. 107, No. 5, 809–824. Published by the American Psychological Association, reprinted with permission.

The American Opportunity Carbon Fee Act is a free market solution that, because it’s revenue-neutral, wouldn’t increase the size of government. All of the revenue generated would be returned to taxpayers through a variety of possible paths:



Fact check: China pledged bigger climate action than the USA; Republican leaders wrong

Posted on 14 November 2014 by dana1981 &

This week, President Barack Obama and Chinese President Xi Jinping unveiled a secretly negotiated agreement for both countries to slow global warming by pledging to reduce carbon pollution. Specifically, President Obama pledged that the USA would cut its carbon pollution 26–28% below 2005 levels by 2025, while President Xi pledged that by 2030, Chinese carbon pollution will peak and 20% of the country’s energy will come from low-carbon sources.

This agreement received predominantly high praise because it represents the world’s two biggest net carbon polluters taking a leading role in committing to tackle the threats posed by human-caused global warming. China in particular is often used as an excuse by those in the United States and around the world who oppose taking steps to slow global warming.

With the announcement of this agreement, the Chinese president has agreed that his country must begin the process of slowing the growth of and eventually reducing its carbon pollution. The common refrain “nothing we do matters unless China acts” is moot.

However, Republican House Majority Leader John Boehner and soon-to-be Senate Majority Leader Mitch McConnell were among the few who issued negative public statements about the climate agreement. McConnell in particular badly misunderstood the practical consequences of the Chinese and American carbon pledges, saying,

As I read the agreement it requires the Chinese to do nothing at all for 16 years while these carbon emissions regulations are creating havoc in my state and around the country,

Senator McConnell misunderstood the Chinese target of reaching peak carbon pollution levels by 2030 as a pledge to “do nothing.” In reality, China has been developing rapidly with hundreds of millions of citizens rising out of poverty, thus demanding more energy. Much of that demand has been met with new coal power plants; China has added one and a half times the entire US coal power plant fleet in just the past decade. As a result, Chinese carbon pollution has been rising fast.

China could not meet its climate pledge by maintaining business-as-usual (BAU) and doing “nothing.” Quite the opposite; curbing those rising carbon emissions as China’s economy continues to grow will require substantial effort. That’s why President Xi also pledged that 20% of the country’s energy would come from low-carbon sources by 2030.

In comparison, the United States will have a relatively easy time meeting the pledge made by President Obama. US carbon pollution is already about 10–15% below 2005 levels and falling by about 1.5% per year. Achieving the target of 26–28% emissions cuts below 2005 levels by 2025 will only require continuing the current rate at which American carbon pollution is already falling.

China and USA carbon dioxide emissions from power generation from 1981 to 2012 (solid lines and squares; data from US Energy Information Administration), pledges (dotted lines), and business-as-usual (BAU) emissions (dashed lines).

China and USA carbon dioxide emissions from power generation from 1981 to 2012 (solid lines and squares; data from US Energy Information Administration), pledges (dotted lines), and business-as-usual (BAU) emissions (dashed lines). Created by Dana Nuccitelli.



We must manage global warming risks by cutting carbon pollution, top scientists conclude

Posted on 10 November 2014 by dana1981 &

Last week, the Intergovernmental Panel on Climate Change (IPCC) published its latest Synthesis Report, summarizing the scientific research on the causes and impacts of global warming, and how we can mitigate its consequences. The report included various graphs showing how we’re changing the Earth’s climate, and concluded that humans are causing rapid and dangerous global warming.

Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.

Much of the report focused on the risks associated with these rapid climate changes. Fundamentally, climate change is a risk management problem. Even if you’re sceptical of the vast body of scientific research pointing to dangerous and potentially catastrophic climate change, there’s a very good chance the experts and their supporting evidence are correct and your scepticism is misplaced. The IPCC report put those risks into perspective,

Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. Limiting climate change would require substantial and sustained reductions in greenhouse gas emissions which, together with adaptation, can limit climate change risks.

Many aspects of climate change and associated impacts will continue for centuries, even if anthropogenic emissions of greenhouse gases are stopped. The risks of abrupt or irreversible changes increase as the magnitude of the warming increases.

The key word here is “irreversible,” and it’s used 14 times in the IPCC’s latest Summary for Policymakers. For example, if ice sheets in Greenland and Antarctica collapse into the ocean, as they’ve already begun to, we can’t take the ice out of the ocean and put it back on land. That lost ice and the sea level rise it causes are irreversible impacts.

Conversely, policies to slow global warming are reversible. A new study by scientists at Duke University found that the widespread rejection of climate science by American political conservatives is in large part due to their distaste for the proposed solutions. Climate contrarians are afraid that climate policies will slow economic growth, despite evidence to the contrary.

However, if it turns out that the sceptics are right in their optimism that the best case climate scenario will occur, and if we go too far in our efforts to reduce carbon pollution, we can easily scale those efforts back. We can’t reanimate extinct species, but we can adjust climate policies as needed.

Speaking of species extinctions, the IPCC discussed that serious threat as well,

A large fraction of species face increased extinction risk due to climate change during and beyond the 21st century, especially as climate change interacts with other stressors (high confidence). Most plant species cannot naturally shift their geographical ranges sufficiently fast to keep up with current and high projected rates of climate change in most landscapes; most small mammals and freshwater molluscs will not be able to keep up at the rates projected under RCP4.5 and above in flat landscapes in this century (high confidence).

Marine species are also at risk due to the dual threats of warming oceans and ocean acidification, both of which are caused by carbon pollution from burning fossil fuels.

Since the beginning of the industrial era, oceanic uptake of CO2 has resulted in acidification of the ocean; the pH of ocean surface water has decreased by 0.1 (high confidence), corresponding to a 26% increase in acidity

The IPCC concluded that if we take serious action to reduce fossil fuel consumption and greenhouse gas emissions, we can limit the future increase in ocean acidity to about 16%. If we continue on a business-as-usual fossil fuel dependent path, ocean acidity will increase by around 100%, with dire consequences for marine ecosystems. This will also hurt our fisheries and contribute to food insecurity.

Climate change is projected to undermine food security (Figure SPM.9). Due to projected climate change by the mid-21st century and beyond, global marine species redistribution and marine biodiversity reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services (high confidence) ... Global temperature increases of ~4°C or more14 above late-20th century levels, combined with increasing food demand, would pose large risks to food security globally (high confidence).

As these figure below from the report also illustrates, about 70% of studies indicate that crop yields will decline as the Earth continues to warm after 2030, with a high chance that yields could decline by 25% or more by the end of the century if we continue on our current path.

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. 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. Illustration: IPCC AR5



Weather Channel co-founder John Coleman prefers conspiracies to climate science

Posted on 4 November 2014 by dana1981 &

The Weather Channel co-founder John Coleman was recently interviewed by Megyn Kelly on Fox News, calling human-caused global warming “a myth.” The interview was then amplified through the media echo chamber, including an article at left-leaning Huffington Post, and Coleman was subsequently interviewed on CNN’s Reliable Sources.

Coleman has publicly denied the scientific reality of human-caused global warming for years, telling Fox News in 2008 that he wanted to sue Al Gore, for example. There’s no new content in these latest interviews; just the usual long-debunked climate myths and conspiracy theories. Coleman is apparently considered a credible climate interviewee because he was instrumental in creating The Weather Channel 32 years ago, but he’s woefully misinformed when it comes to climate science.

Coleman Denies Basic Climate Science

In his Fox News interview, Coleman said,

The Antarctic ice cap is at an all-time record high in both coverage and thickness, and the Arctic ice cap at the North Pole is at the highest it has been in several years. It’s in its so-called normal range since we got satellite observations that can measure it. So not only is the ice not melting, more polar bears are alive and happy today than in 100 years.

Each of these points is either wrong or misleading.

Although more Arctic sea ice survived this year than in the record-shattering melt of 2012, in 2014 the ice was nevertheless at its 6th-lowest level in thousands of years. About 70% of the sea ice in the Arctic has disappeared over the past three decades, mainly due to human-caused global warming. This rapid decline is well outside “the normal range” of Arctic sea ice extent and volume.

Reconstructed Arctic sea ice extent over the past 1,450 years, from Kinnard et al. (2011). Reconstructed Arctic sea ice extent over the past 1,450 years, from Kinnard et al. (2011).



Republican politicians aren't climate scientists or responsible leaders

Posted on 28 October 2014 by dana1981 &

Republican Senate Minority Leader Mitch McConnell is hoping to become the Senate Majority Leader after the forthcoming election on November 4th, although despite hailing from conservative Kentucky, McConnell is in a very tight race. The Cincinnati Enquirer editorial board recently had a long discussion with McConnell and tried to pin him down on the subject of global warming.

McConnell wouldn’t directly answer whether he believes in climate change.

Enquirer’s editorial board volleyed several questions about what it would take to convince him of climate change. He turned the subject every time to jobs. McConnell said he believes imposing regulations to reduce greenhouse gases blamed for climate change would only hurt America and not mitigate what other countries, such as China, are doing...

“We can debate this forever,” McConnell said. “George Will had a column in the last year or so pointing out that in the 70s, we were concerned the ice age was coming. I’m not a scientist. I’m interested in protecting Kentucky’s economy.”

Leaving aside McConnell’s reference to the 1970s ice age myth, the cop-out about not being a scientist is a strange and dangerous one.



2014 Arctic sea ice extent - 6th lowest in millennia

Posted on 23 October 2014 by dana1981 &

The National Snow and Ice Data Center has reported that this year we saw the 6th-lowest minimum Arctic sea ice extent on record. Research has shown that most of the long-term decline in sea ice, or the “death spiral” as it’s come to be known, is due to human-caused global warming.

Natural factors play a role in the extent of the Arctic sea ice as well, especially changes in weather conditions on a year-to-year basis. For example, 2012 shattered the previous record low Arctic sea ice extent because on top of the human influences, the weather conditions were ripe for a dramatic decline that year. In 2013 and 2014, weather conditions were closer to normal, so they didn’t break the 2012 record. As a result, the usual suspects have declared that Arctic sea ice is now “expanded” compared to 2 years ago.

The flaw in that argument is illustrated in this animated graphic I created.

sea ice escalator

September Arctic sea ice extent data since 1980 from the National Snow and Ice Data Center (blue diamonds).  "Recovery" years, meaning years when the sea ice extent is greater than the previous year, are highlighted in red to mock the repeated cynical claims of climate change "skeptics" that global warming has somehow stopped.



Dinner with global warming contrarians, disaster for dessert

Posted on 13 October 2014 by dana1981 &

Twelve climate scientists and contrarians recently had dinner together in the UK, which for some reason received media attention. While everyone should be free to have dinner with whomever they like, the problem with this particular event was that the ensuing media coverage made the contrarians seem downright reasonable. For example, the article about the dinner stated,

“...the insults slung around online only hinder the process of rational scientific debate.”

Yet one of the contrarians attending the dinner was Anthony Watts, who runs a blog that regularly insults climate scientists and climate realists. In fact, just a few days after the dinner, Watts was already taunting Ben Santer, one of the world’s most highly respected climate scientists, who had previously treated Watts with courtesy and respect. The article also quoted Watts as saying,

We’ve been at odds so long, it is time to present science together,

Climate contrarians are already free to present science at climate conferences. For example, the annual American Geophysical Union (AGU) fall meeting is the largest gathering of climate scientists presenting and discussing their research. Every year, the vast majority of scientific research presented at the AGU conference and others like it (about 97% or so) is consistent with the expert consensus on human-caused global warming. Contrarians don’t present science there because they have so little science to present.

The Mail on Sunday’s David Rose also attended the dinner. His latest climate article focused on the slight increase in Arctic sea ice as compared to the record low of two years ago (and of course on Al Gore), while ignoring the fact that the Arctic has lost about 70% of its total volume of sea ice over the past three decades.



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