Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


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.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest

RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

Keep me logged in
New? Register here
Forgot your password?

Latest Posts


Climate Hustle


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.

Dana has been researching climate science, economics, and solutions since 2006, and has contributed to Skeptical Science since September, 2010.  He also blogs at The Guardian, and is the author of Climatology versus Pseudoscience.  He has published climate-related papers on various subjects, from the build-up of heat in the Earth's climate system to the expert consensus on human-caused global warming.

Follow 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., Oreskes, N., Doran, P. T., Anderegg, W. R., Verheggen, B., Maibach, E. W., Carlton, J. S., Lewandowsky, S., Skuce, A. G., Green, S. A., & Nuccitelli, D. (2016). Consensus on consensus: a synthesis of consensus estimates on human-caused global warming. Environmental Research Letters, 11(4), 048002.

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

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.

Abraham, J., Cook, J., Fasullo, J., Jacobs, P., Mandia, S., & Nuccitelli, D. (2014). Review of the consensus and asymmetric quality of research on human-induced climate changeCosmopolis2014(1), 3-18.

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

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

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


Recent blog posts

We’re now breaking global temperature records once every three years

Posted on 23 January 2017 by dana1981 &

According to Nasa, in 2016 the Earth’s surface temperature shattered the previous record for hottest year by 0.12°C. That record was set in 2015, which broke the previous record by 0.13°C. That record had been set in 2014, beating out 2010, which in turn had broken the previous record set in 2005.

If you think that seems like a lot of record-breaking hot years, you’re right. The streak of three consecutive record hot years is unprecedented since measurements began in 1880. In the 35 years between 1945 and 1979, there were no record-breakers. In the 37 years since 1980, there have been 12. The video below illustrates all of the record-breaking years in the Nasa global surface temperature record since 1880.

Nasa global surface temperature data, with record-breaking years shown in red. Created by Dana Nuccitelli.



Fact Check: Rex Tillerson on Climate Risks

Posted on 16 January 2017 by dana1981 &

President-elect Donald Trump’s nominee for Secretary of State – and until recently the CEO of ExxonMobil – Rex Tillerson was given a confirmation hearing by the Senate Foreign Relations Committee last week. In his testimony, Tillerson accepted the reality of human-caused global warming and that “The risk of climate change does exist and the consequences of it could be serious enough that action should be taken.”

While he accepted the problem exists, Tillerson nevertheless proceeded to downplay its risks, saying:

The increase in the greenhouse gas concentrations in the atmosphere are having an effect, our ability to predict that effect is very limited.

Many climate scientists took issue with that statement, and for good reason. Climate models have been very accurate in their projections about many consequences of human carbon pollution. It’s true that there’s uncertainty in just how quickly some of those consequences will be triggered. The bad news is that recent studies have shown that many of those consequences are happening more quickly than climate scientists anticipated. Greater climate uncertainty translates into more urgency to tackle the problem, not less.

The Gulf Stream could shut down sooner than anticipated

The Gulf Stream – which keeps the UK and surrounding area significantly warmer than it would otherwise be – is part of the Atlantic Meridional Overturning Circulation (AMOC). Research has shown it could shut down as a result of global warming:

In 1997, the oceanographer Wallace Broecker, of Columbia University in New York, suggested that if the Gulf stream turned off, winter temperatures in the British Isles could fall by an average of 11°C - plunging Blackpool or Berwick to the same temperatures as Spitsbergen, inside the Arctic circle. Any dramatic drop in temperature could have devastating implications for agriculture - and for Europe’s ability to feed itself.

Just how quickly such a shutdown could happen has been a subject of debate and research among climate scientists. A study published in Science Advances in early January corrected for a bias recently identified in climate models that acted to keep the AMOC and Gulf Stream more stable than it appears to be in reality:



Conservative media can't stop denying there was no global warming 'pause'

Posted on 10 January 2017 by dana1981 &

Scientists have proven time and time again that global warming continues unabated. Most recently, a study published last week showed that over the past two decades, the oceans have warmed faster than prior estimates. This study affirmed the findings of a 2015 NOAA paper – not surprisingly attacked by deniers – that removed a cool bias in the data, finding there never was a global warming “pause.”

This particular myth has been a favorite of deniers over the past decade for one simple reason – if people can be convinced that global warming stopped, they won’t consider it a threat that we need to urgently address by cutting fossil fuel consumption. It’s thus become one of the most common myths peddled by carbon polluters and their allies.

One of those allies is the anti-climate policy advocacy group Global Warming Policy Foundation (GWPF), which tries to make the case that aggressive climate policy isn’t needed. This weekend, its “science” editor David Whitehouse wrote for the conservative UK Spectator periodical – which often promotes climate denial – denying that the “pause” is dead:

their case rests on the El Nino temperature increase and will be destroyed when the El Nino subsides, as it is currently doing. A temporary victory over the ‘pause’.

The ‘pause’ can be accommodated into global warming – but not for very much longer. The world’s temperature has to increase outside the El Nino effect.

Testing the myth

If Whitehouse is correct and temperatures are not increasing outside the El Niño effect, then 2015 and 2016 should be no hotter than previous El Niño years. It’s a relatively simple test to run. In the video below, I’ve broken out the temperature data into years with an El Niño warming influence, years with a La Niña cooling influence, and neutral years.



Prepare for reanimation of the zombie myth ‘no global warming since 2016’

Posted on 6 January 2017 by dana1981 &

Climate myths are like zombies – you shoot them through the heart, walk away thinking they’re dead, and then they pop back up behind you and try once again to eat your brain.

So it is with Stage 1 climate denial and the myth that the Earth isn’t warming. It’s so persistent that it’s related to the 5th, 9th, and 49th-most popular myths in the Skeptical Science database. Climate deniers have been peddling the myth ‘no warming since [insert date]’ for over a decade.

It’s a popular myth among those who benefit from maintaining the status quo because if the problem doesn’t exist, obviously there’s no need for action to solve it. And it’s an incredibly easy argument that can be made at any time, using the telltale technique of climate denial known as cherry picking.

I created a video to illustrate this point. The key is that the Earth has natural short-term temperature oscillations caused by factors like the El Niño/La Niña cycle. El Niño events temporarily warm temperatures at the Earth’s surface, while La Niña events cause temporary surface cooling. When you combine these up-and-down cycles with a long-term human-caused global warming trend and various other noisy influences, you get a bumpy temperature rise that allows for cherry picking of periods without warming:

That’s what it looks like with artificial data. Using real global surface temperature data from NASA, I created a popular graphic called The Escalator, which has been featured the PBS documentary Climate of Doubt and used by Senator Sheldon Whitehouse on the Senate floor. The video below shows The Escalator with data updated through 2016:



Facts matter, and on climate change, Trump's picks get them wrong

Posted on 27 December 2016 by dana1981 &

When speaking about climate change, President-elect Trump has flip-flopped between acceptance and denial, which suggests that he hasn’t put much thought into one of humanity’s greatest threats. However, what his administration does is far more important than what he thinks. Unfortunately, Trump has nominated individuals to several critical climate leadership positions who reject inconvenient scientific and economic evidence.

Stage 3 denial: climate dangers and model accuracy

Climate denial often pinballs between five different stages, but the cleverer denialist arguments tend to land on Stage 3: denial that climate change is a problem.

It’s ironic that Secretary of State nominee Rex Tillerson – CEO of ExxonMobil – has the most sophisticated position on climate change among Trump’s key nominees. Tillerson accepts that humans are causing global warming, but he denies that it’s a problem. His key argument focuses on sowing doubt about the accuracy of climate models.

This happens to be the core topic in my book Climatology versus Pseudoscience, whose analysis I updated for a presentation at the American Geophysical Union conference two weeks ago. Climate scientists have been making global temperature predictions for over 40 years, and they’ve turned out to be amazingly accurate, as this video of the key slides from my presentation shows:

Various global temperature projections by mainstream climate scientists and models, and by climate contrarians, compared to observations by NASA GISS. Created by Dana Nuccitelli.



Russian email hackers keep playing us for fools

Posted on 22 December 2016 by dana1981 &

A batch of stolen emails was released to the public, with evidence pointing towards Russian hackers. The media ran through the formerly private correspondence with a fine-toothed comb, looking for dirt. Although little if any damning information was found, public trust in the hacking victims was severely eroded. The volume of media coverage created the perception that where there’s smoke, there must be fire, and a general presumption of guilt resulted.

The year was 2009, and the victims were climate scientists working for and communicating with the University of East Anglia. The story was repeated in 2016 with the Russian hacking of the Democratic National Committee.

The faux scandal known as “Climategate”

After 1,000 of climate scientists’ private emails were stolen and published online, snippets of text were taken out of context and misrepresented to falsely accuse the scientists of scandal, conspiracy, collusion, falsification, and illegal activities. Climate deniers and biased media outlets whipped up such froth over these misrepresentations that various organizations launched nine separate investigations to identify any possible scientific wrongdoing uncovered by the emails. They found none.

Nevertheless, “Climategate” caused temporary erosion in public trust of climate scientists. Like most such news events, people quickly forgot and the effect soon faded; however, the stolen emails were made public just a month before the Copenhagen international climate summit. The well-timed release of the hacked emails provided a distraction that helped sink the negotiations, which were generally viewed as a failure. A serious international climate agreement was delayed for another six years.

Clinton’s campaign was similarly sunk

Similarly, the stolen emails released by Wikileaks did not identify any damning revelations about Hillary Clinton. The leaks had the desired effect – Clinton’s emails received three times more nightly news network coverage than all policy issues combined.




This is not normal – climate researchers take to the streets to protect science

Posted on 16 December 2016 by dana1981 &

Desperate times call for desperate measures, and for scientists, these are desperate measures.

Tuesday in San Francisco’s Jessie Square, approximately 500 people gathered for a ‘rally to stand up for science.’ Many of the attendees were scientists who had migrated to the rally from the nearby Moscone Center, where some 26,000 Earth scientists are attending the annual American Geophysical Union (AGU) conference this week.

This was an unusual activity for scientists to participate in; after all, they’re often accused of remaining isolated in the ivory towers of academia. Scientists generally prefer to focus on their scientific research, use their findings to inform the public and policymakers, and leave it to us to decide what actions we should take in response. In fact, one of the keynote speakers at the rally, Harvard science historian Naomi Oreskes made that exact point:

We don’t want to be here. We want to be doing the work we were trained and educated to do, which is science ... but we are at a moment in history where we have to stand up.

As Georgia Tech climate scientist Kim Cobb noted, with the appointments made thus far by the incoming Trump administration, science is under attack and scientists feel compelled to protect their research, and their ability to keep doing it. Cobb also called on more of her scientific colleagues to step outside their comfort zones and engage in activism:

Kim Cobb speaking at the rally to stand up for science. Video by Collin Maessen of

The rally followed other recent efforts by scientists to advise the Trump administration and reassure the public. For example, over 800 Earth scientists and energy experts signed a letter urging the President-elect to take six key steps to address climate change:



On climate change, angels and demons are battling over Trump’s soul

Posted on 12 December 2016 by dana1981 &

There are signs that a war may be brewing over President-elect Donald Trump’s climate legacy, and the bad guys are winning.

In one corner: Team Ivanka

His daughter Ivanka appears to be establishing a role as the one person who might prevent the Trump administration from undoing all of the progress made by the Obama administration in cutting US carbon pollution, and instead establishing policies that will maximize the country’s burning of fossil fuels. According to Politico, Ivanka Trump wants to make climate change one of her signature issues. She recently coordinated meetings between the president-elect and Al Gore and Leonardo DiCaprio.

DiCaprio in particular wisely focused his presentation on the fact that a shift to clean renewable energy would create millions of jobs. The best way to help a businessman like Donald Trump appreciate the importance and benefits of cutting carbon pollution is to focus on the economic opportunities presented by the coming green technology revolution. It’s an opportunity that China is poised to seize upon, as UCLA Law School’s Alex Wang noted:

Climate change regulation is seen as an economic tool aimed at moving China’s economy toward the low-carbon, high-tech, and clean energy industries of the future. China would like nothing more than to have the U.S. retreat from clean energy innovation and allow it to step into the breach.



Fake news tries to blame human-caused global warming on El Niño

Posted on 5 December 2016 by dana1981 &

Human carbon pollution is heating the Earth incredibly fast. On top of that long-term human-caused global warming trend, there are fluctuations caused by various natural factors. One of these is the El Niño/La Niña cycle. The combination of human-caused warming and a strong El Niño event are on the verge of causing an unprecedented three consecutive record-breaking hot years

Simply put, without global warming we would not be seeing record-breaking heat year after year. In fact, 2014 broke the temperature record without an El Niño assist, and then El Niño helped push 2015 over 2014, and 2016 over 2015.

Sadly, we live in a post-truth world dominated by fake news in which people increasingly seek information that confirms their ideological beliefs, rather than information that’s factually accurate from reliable sources. Because people have become incredibly polarized on the subject of climate change, those with a conservative worldview who prefer maintaining the status quo to the steps we need to take to prevent a climate catastrophe often seek out climate science-denying stories.

Into that environment step conservative columnists David Rose at the Mail on Sunday, parroted by Ross Clark in The Spectator and James Delingpole for Breitbart, all trying to blame the current record-shattering hot global temperatures entirely on El Niño. Perhaps saddest of all, the House Science, Space, and Technology Committee tweeted the Breitbart piece, to which Senator Bernie Sanders appropriately responded:

An über cherry-picked argument

The conservative columnists made their case by claiming that, with the recent strong El Niño event ending, temperatures are “plummeting,” thus blaming the record heat on El Niño. There are several fatal flaws in their case.

First, the “plummet” they cite is not in global temperatures on the surface where we live, and where temperatures are easiest to measure accurately, but rather in satellite estimates of the temperature of the lower atmosphere above the portions of Earth’s surface covered by land masses. Second, although the satellite data extend as far back as 1979, and the global surface temperature data to 1880, they cherry pick the data by only showing the portion since 1997. Third, the argument is based entirely upon one relatively cool month (October 2016) that was only cool in that particularly cherry-picked data set.

The argument is easily debunked. While there was a strong El Niño event in 2015–2016, there was an equally strong event in 1997–1998. The two events had very similar short-term warming influences on global surface temperatures, but according to Nasa, 2016 will be about 0.35°C hotter than 1998. That difference is due to the long-term, human-caused global warming trend. In fact, according to Nasa, even October 2016 was hotter than every month on record prior to 1998. These “plummeting” post-El Niño temperatures are still as hot as the hottest month at the peak of the 1998 El Niño.

monthly temps



Trump and the GOP may be trying to kneecap climate research

Posted on 30 November 2016 by dana1981 &

Last week, Donald Trump’s space policy advisor Bob Walker made headlines by suggesting that the incoming administration might slash Nasa’s climate and earth science research to focus the agency on deep space exploration. This caused great concern in the scientific community, because Nasa does some of the best climate research in the world, and its Earth science program does much more. Walker suggested the earth science research could be shifted to other agencies, but climate scientist Michael Mann explained what would result:

It’s difficult enough for us to build and maintain the platforms that are necessary for measuring how the oceans are changing, how the atmosphere is changing, with the infrastructure that we have when we total up the contributions from all of the agencies ... we [could] lose forever the possibility of the continuous records that we need so that we can monitor this planet.

Walker’s comments set off alarm bells for another reason. Were it simply a matter of transferring Nasa’s climate and earth science programs to other agencies, what would be the point? Such a transfer would be logistically difficult, and if the research funding weren’t cut, it wouldn’t save any taxpayer money. And it’s not as though the branches doing Nasa’s climate research are distracting other branches of the agency from conducting deep space exploration.

The suggestion does however look a lot like a Trojan horse whose true purpose is to cut government-funded climate research, perhaps transferring some of Nasa’s programs and budget to other agencies and simply scrapping the rest.

Bob Walker’s politicized science

In an interview with The Guardian, Walker accused Nasa of “politically correct environmental monitoring” and “politicized science.” Carol Off from CBC’s program As It Happens conducted a follow-up interview with Walker and asked for examples to support his accusations. Walker cited the example of Nasa’s announcement that 2014 was the hottest year on record, claiming:



The Consensus Project Website



(free to republish)



The Scientific Guide to
Global Warming Skepticism

Smartphone Apps


© Copyright 2017 John Cook
Home | Links | Translations | About Us | Contact Us