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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

Sen Whitehouse Schools Sen Inhofe about Global Warming on the Senate Floor

Posted on 31 July 2014 by dana1981 &

Senator Sheldon Whitehouse (D-RI) throws down an epic schooling of Senator James Inhofe (R-OK) on global warming after Inhofe blocked a resolution from Senator Amy Klobuchar (D-MN) simply acknowledging that global warming exists and poses a threat to the interests of the United States.  Whitehouse makes several points that seem to originate from Skeptical Science, like The Escalator steps.  Well worth taking 7 minutes to watch - hat tip to Phil Plait at Bad Astronomy.



Nigel Lawson suggests he's not a skeptic, proceeds to deny global warming

Posted on 28 July 2014 by dana1981 &

Nigel Lawson is the chairman of the Global Warming Policy Foundation; a political group that regularly releases selective scientific reports about climate change. The organization consistently tries to argue that concerns about global warming – concerns that are based on the full body of scientific evidence – are overblown, which would imply that there's less urgency to solve the climate problem.

In a recent interview with The Independent, Lawson implied that he doesn't consider himself "a climate-change sceptic," but immediately proceeded to deny that the planet is warming, and reject mainstream scientific estimates of the climate sensitivity to the increased greenhouse effect.

There is no global warming to speak of going on at the moment. If you look at the Met Office statistics, that's quite clear. But there could be, there clearly could. If it does happen, there would be a much slower process than the alarmists pretend.

The first statement is untrue on several levels. First, even the Met Office HadCRUT4 estimates of global surface temperatures show we're still in the midst of a warming trend (you can easily check the data for yourself with this tool). Second, the Met Office estimates have a known cool bias due to a lack of coverage in the Arctic, and estimates correcting for that bias show an even larger surface warming trend.

Third and most importantly, the atmosphere only accounts for about 2% of the warming of the planet as a whole. Over 90% of global warming goes into heating the oceans. Studies that account for the warming of the entire global climate have found that it continues unabated. In fact, the planet has built up heat at a rate equivalent to 4 Hiroshima atomic bomb detonations per second over the past 15 years.

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



Climate models accurately predicted global warming when reflecting natural ocean cycles

Posted on 21 July 2014 by dana1981 &

Predicting global surface temperature changes in the short-term is a challenge for climate models. Temperature changes over periods of a decade or two can be dominated by influences from ocean cycles like El Niño and La Niña. During El Niño phases, the oceans absorb less heat, leaving more to warm the atmosphere, and the opposite is true during a La Niña.

We can't yet predict ahead of time how these cycles will change. The good news is that it doesn't matter from a big picture climate perspective, because over the long-term, temperature influences from El Niño and La Niña events cancel each other out. However, when we examine how climate model projections have performed over the past 15 years or so, those natural cycles make a big difference.

A new paper led by James Risbey just out in Nature Climate Change takes a clever approach to evaluating how accurate climate model temperature predictions have been while getting around the noise caused by natural cycles. The authors used a large set of simulations from 18 different climate models (from CMIP5). They looked at each 15-year period since the 1950s, and compared how accurately each model simulation had represented El Niño and La Niña conditions during those 15 years, using the trends in what's known as the Niño3.4 index.

Each individual climate model run has a random representation of these natural ocean cycles, so for every 15-year period, some of those simulations will have accurately represented the actual El Niño conditions just by chance. The study authors compared the simulations that were correctly synchronized with the ocean cycles (blue data in the left frame below) and the most out-of-sync (grey data in the right frame) to the observed global surface temperature changes (red) for each 15-year period.

The red dots on the thin red line correspond to the 15-year observed trends for each 15-year period.  The blue dots show the 15-year average trends from only those CMIP5 runs in each 15-year period where the model Niño3.4 trend is close to the observed Niño3.4 trend. The grey dots show the average 15-year trends for only the models with the worst correspondence to the observed Niño3.4 trend.  The size of the dots are proportional to the number of models selected.  The envelopes represent 2.5–97.5 percentile loess-smoothed fits to the models and data. Red: 15-year observed trends for each period. Blue: 15-year average trends from CMIP5 runs where the model Niño3.4 trend is close to observations. Grey: average 15-year trends for only the models with the worst correspondence to the Niño3.4 trend. The sizes of the dots are proportional to the number of models selected. From Nature Climate Change



Rupert Murdoch doesn't understand climate change basics, and that's a problem

Posted on 14 July 2014 by dana1981 &

Rupert Murdoch has a vast media empire. In the UK, his News Corp assets include The Times and The Sun. In the USA, he has Fox News, The New York Post, and The Wall Street Journal. In Australia, he's got The Australian and a multitude of local newspapers.

Many of Murdoch's news outlets are also among the worst when it comes to getting climate science wrong and disseminating climate myths and misinformation. Inaccurate media coverage is in turn the primary reason why the public is so misinformed about global warming.

In a recent Sky News interview, Rupert Murdoch expressed his own views about global warming and climate change.

Murdoch's most inaccurate statement was,

In terms of the world's temperature going up, the worst, the most alarmist things have said ... 3°C in 100 years. At the very most one of those will come from man-made, be man-made.

In reality, the worst case scenario considered by the 2014 IPCC report projects about 4°C global surface warming over the next century (on top of the nearly 1°C that we've already caused). All of that 4°C warming would be human-caused. The best case scenario would involve about 1°C global surface warming over the next century, and that's if we take serious action to reduce carbon pollution.

IPCC AR5 projected global average surface temperature changes in a high emissions scenario (RCP8.5; red) and low emissions scenario (RCP2.6; blue). IPCC AR5 projected global average surface temperature changes in a high emissions scenario (RCP8.5; red) and low emissions scenario (RCP2.6; blue).



Rose-colored glasses: Antarctic sea ice is the Mail on Sunday's latest global warming distraction

Posted on 7 July 2014 by dana1981 &

David Rose and The Mail on Sunday produce the most reliable global warming journalism, in the sense that they can be relied upon to consistently misrepresent climate science. Their latest piece focuses on Antarctic sea ice.

You might wonder why we should particularly care about Antarctic sea ice. The answer is that it provides a nice distraction from rapidly declining Arctic sea ice, glaciers around the world, the Antarctic and Greenland ice sheets, the warming oceans, the warming atmosphere, and so on. Antarctic sea ice has bucked these trends by modestly increasing in extent and volume.

To put this increase in context, the volume of Antarctic sea ice has risen by about 7.5% since 1992, according to a recent study. The volume of Arctic sea ice, on the other hand, has declined by about 75% since 1980. Antarctica has been gaining about 30 cubic kilometers (km3) of sea ice volume per year, while the Arctic has been losing 10 times as much – 300 km3 per year.



'Reform conservatism' is not enough reform on global warming

Posted on 2 July 2014 by dana1981 &

The conservative YG Network recently published a series of ‘reform conservative’ essays called ‘Room to Grow,’ designed to create a ‘thriving middle class’ while limiting the size of government. Those essays have been subject to intense criticism from Vox’s Matt Yglesias and New York Magazine’s Jonathan Chait for failing to even mention climate change despite devoting a chapter to energy policies. Adam White, author of that energy policy chapter, pushed back by arguing,

There's no shortage of talk about climate change—its causes, its dangers, and the challenges and costs of regulating it.

Unfortunately, in terms of conservative climate policies, that’s not an accurate statement. When it comes to global warming, today’s conservative American policymakers most often deny the scientific evidence that climate change is a problem to begin with. When discussions are able to move beyond the stage of science denial, conservative policymakers will generally assert – without any supporting evidence – that climate policies will kill jobs and cripple the economy. In reality, studies have shown that the opposite is true: smart climate policies can have minimal economic impact and even grow the economy.



Global warming conspiracy theorist zombies devour Telegraph and Fox News brains

Posted on 25 June 2014 by dana1981 &

A long-debunked myth is amplified by the conservative media echo chamber from a fringe science-denying blog to The Telegraph and Fox News

A man dressed up as a zombie takes part in a "Zombie Walk" at the Revolution Monument in Mexico City on November 3, 2012.

A man dressed up as a zombie takes part in a "Zombie Walk" at the Revolution Monument in Mexico City on November 3, 2012. Photograph: Alfredo Estrella/AFP/Getty Images

Global warming myths can never be permanently killed. Once debunked, a climate myth will go into a state of hibernation, waiting for enough time to pass that people forget the last time a scientific stake was thrust through its heart. The myth will eventually rise from the grave once again, seeking out victims with tasty, underutilized brains to devour – every zombie’s favorite meal.



Why we care about the 97% expert consensus on human-caused global warming

Posted on 24 June 2014 by dana1981 &

Three distinct studies using four different methods have independently shown that the expert consensus on human-caused global warming is 97 ± 1%. The result is the same whether we ask the experts’ opinions, look at their public reports and statements, or examine their peer-reviewed science. Even studies that quibble about the precise percentage have accidentally reinforced the 97 ± 1% consensus.

The evidence is crystal clear that humans are the main cause of the current global warming, and the expert consensus reflects the strength of that body of evidence. It’s not easy to convince 97% of scientific experts about anything – that requires some powerful scientific evidence.

And yet public opinion is a very different story. Americans think experts are evenly split on the causes of global warming. The public is likewise split on the cause of global warming, with just over half understanding that humans are primarily responsible. As a result, Americans don’t see global warming as an urgent issue, putting climate policy low on the list of priorities.

The sources of this disparity and how it can be corrected are the subjects of an intense debate amongst social scientists. One school of thought says that we have a problem with ‘information deficit’ as well as what climate scientist Michael Mann calls ‘misinformation surplus.’

For example, experimental evidence shows that if people are presented with a basic explanation of how global warming works, they’re more likely to accept the reality of human-caused global warming. Other research has shown that if people are told about the expert consensus, they’re also more likely to accept the science. In both cases, presenting people with certain pieces of information trims the gap between what the scientific evidence and experts say, and what the public believes.

The other school of thought, led by Dan Kahan at Yale, argues that the problem boils down to cultural biases. In essence, liberals feel as though they’re on Team ‘global warming is a problem caused by humans’ while conservatives identify with Team ‘no it’s not.’ Kahan feels that people will take any new information and pass it through their cultural filter; if it conforms to their cultural identity, they’ll accept it, or otherwise they’ll just reject it. In fact, Kahan argues that giving people information that doesn’t conform to their cultural identity (like the 97% consensus) may just act to polarize them further.

In a recent editorial for The Guardian, Adam Corner made a similar argument, asking 'who cares about the climate change consensus?'. Corner suggested that climate information is ineffective if it’s not coming from “communicators whose cultural credentials are congruent with the audience they are speaking to.” Both Kahan and Corner have also argued that if consensus messaging could work, then it should have worked by now, whereas American public acceptance of human-caused global warming in 2014 is lower than in 2003.

Gallup poll results on the perceived causes of global warming. Gallup poll results on the perceived causes of global warming.



In charts: how a revenue neutral carbon tax cuts emissions, creates jobs, grows the economy

Posted on 13 June 2014 by dana1981 &

A revenue-neutral carbon tax or fee is a proposed policy to address global warming that's become increasingly popular, particularly in the US. It's a simple concept – put a much needed price on carbon pollution, but return all the revenue that's generated to taxpayers (for example with a monthly refund) to offset rising energy costs. This approach appeals to political conservatives, because it's a free market solution that doesn't increase the size of government.

British Columbia (BC) launched a revenue-neutral carbon fee in 2008, with the tax offset through a matching reduction income taxes. So far it's been very successful, decreasing carbon pollution while the BC economy performed just as well as the rest of Canada's. The carbon tax has 64% support among BC voters.

The main source of opposition to carbon pricing is the perception that it will 'kill jobs' or otherwise hurt the economy. However, economic forecasts have rarely been done for a carbon fee in which 100% the revenue is returned to the taxpayers. Under proposed revenue-neutral carbon tax legislation, about two-thirds of taxpayers are projected to receive more in refunds than they pay in higher energy prices. It's a net financial gain for most people. This is a key factor that differentiates a revenue-neutral carbon tax system and its economic impacts from other carbon pricing systems.

A new study from Regional Economic Models, Inc. (REMI) models this type of policy. REMI has been developing regional forecasting and policy analysis models since 1980. In their study (full report here, summary here), REMI modeled the regional and national economic impacts of a revenue-neutral carbon tax starting at a modest $10 per metric ton of carbon dioxide in 2016, growing steadily by $10 per year each year. They broke the US into nine distinct geographic regions.

The nine regions in the REMI study (Alaska and Hawaii are in the Pacific region) The nine regions in the REMI study (Alaska and Hawaii are in the Pacific region)



Richard Tol accidentally confirms the 97% global warming consensus

Posted on 4 June 2014 by dana1981 &

An updated version of this post has been published at The Guardian


“There is no doubt in my mind that the literature on climate change overwhelmingly supports the hypothesis that climate change is caused by humans. I have very little reason to doubt that the consensus is indeed correct.”

These are the words of economist and Global Warming Policy Foundation advisor Richard Tol in a new paper published in Energy Policy. Despite accepting that the expert consensus on human-caused global warming is real and correct, Tol has nevertheless spent the past year trying to critique the study the Skeptical Science team published last year, finding a 97% consensus in the peer-reviewed climate literature.

The crux of Tol's paper is that he would have conducted a survey of the climate literature in a slightly different way than our approach. He's certainly welcome to do just that – as soon as we published our paper, we also launched a webpage to make it as easy as possible for anyone to read the same scientific abstracts that we looked at and test the consensus for themselves.

Tol chose instead to look for faults in our study's methods in what he described as a "destructive" approach. Ultimately he concluded that because those who were categorizing the abstracts based on their position on the cause of global warming were human, our ratings were imperfect (this is certainly true), and that accounting for these imperfections brings the consensus value down to about 91%. That's where Tol made his big mistake.

Tol's big mistake

To minimize our uncertainties, we had at least two people categorize each scientific abstract. Where those two raters disagreed, we had a reconciliation process. The disagreeing raters first checked their ratings again; if the disagreement persisted, a third person acted as the tiebreaker to establish the final rating.

Using the difference between our initial and final ratings, it's possible to estimate the number of papers that still remain in the improper categories after our reconciliation process. Tol put the estimate at about 6.7% of the total, and noted that 55% of our reconciliations from initial to final ratings were 'towards stronger rejection', while 45% were 'towards stronger endorsement' of human-caused global warming.

Tol then made a basic and critical error. His methodology resulted in assumptions that, for example, 55% of the remaining incorrectly rated 'no position' category papers should actually be rejections, while 45% should be endorsements. He didn't check to see how the reconciliations changed the initial and final ratings for each category, and this assumption led him to incorrectly conclude the consensus is actually 91%. Still a high percentage, but nonetheless in error.

In reality, as our response to Tol's critique (accepted by Energy Policy but not yet published) shows, there simply aren't very many peer-reviewed papers that minimize or reject human-caused global warming. Most of the papers that were reconciled 'towards stronger rejection' went from explicit to implicit endorsement, or from implicit endorsement to no position. For abstracts initially rated as 'no position,' 98% of the changes were to endorsement categories; only 2% were changed to rejections.

That makes sense when you think about it, because less than 3% of all climate papers reject or minimize human-caused global warming. There's no reason to expect 55% of incorrectly rated 'no position' papers to reject the consensus – in reality there just aren't that many rejection papers. I asked Tol about this point, and he responded,

"I indeed use the marginal distribution of error corrections rather than the conditional ones. There are not enough observations to estimate all the conditionals."

However, the 'no position' category was the largest in our sample, and was the main source of Tol's mistaken calculation, as shown in the figure below. The top frame illustrates the result when calculation is done correctly using the actual reconciliations for each category, while the bottom frame shows the result using Tol's faulty assumptions.

Recalculated consensus based on actual paper reconciliations (top frame), and based on Tol's erroneous assumptions (bottom frame)

Recalculated consensus based on actual paper reconciliations (top frame), and based on Tol's erroneous assumptions (bottom frame)

An anonymous individual has also published an elegant analysis showing that Tol's method will decrease the consensus no matter what data are put into it. In other words, his 91% consensus result is an artifact of his flawed methodology.



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