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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

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

Matt Ridley wants to gamble the Earth’s future because he won’t learn from the past

Posted on 21 January 2015 by dana1981 &

Have you ever watched a zombie movie and wondered if the protagonists will grow physically tired from having to repeatedly kill zombies that inevitably rise once again from the dead? That’s how people often feel when confronted with climate change myths that were debunked years ago. These myths never seem to stay dead, inevitably being revived by climate contrarians no matter how conclusively and repeatedly they’ve been debunked.

And so we have writer Matt Ridley once again published in the London Times complaining, “Rather than attack my arguments, my critics like to attack my motives.” That’s undoubtedly because when an individual keeps repeating the same myths over and over again, people eventually grow tired of debunking those myths and naturally question the motives of the individual who keeps making them.

Let’s look at a few examples from Ridley’s latest article. He claims not to be worried about global warming for a few reasons, including,

The failure of the atmosphere to warm anywhere near as rapidly as predicted was a big reason: there has been less than half a degree of global warming in four decades - and it has slowed down, not speeded up.

This is incorrect – average global surface temperatures have warmed between 0.6 and 0.7°C over the past 40 years (lower atmospheric temperatures have also likely warmed more than 0.5°C, though the record hasn’t yet existed for 40 years). During that time, that temperature rise has temporarily both slowed down (during the 2000s, when there was a preponderance of La Niña events) and sped up (during the 1990s, when there was a preponderance of El Niño events). Climate models accurately predicted the long-term global warming trend. Ridley continues,



Global warming made 2014 a record hot year – in animated graphics

Posted on 17 January 2015 by dana1981 &

But what’s really remarkable is that 2014 set this record without the aid of an El Niño event. El Niño events create conditions in which sea surface and hence global surface temperatures are anomalously hot. We call this part of the Earth’s “internal variability” because these events just temporarily shift heat around between the ocean surface and its depths.

As this graphic shows (click here for an animated version), the last five record hot years of 2010, 2005, 1998, 1997, and 1995 were all assisted by El Niño events.

ENSO Temps



Economics supports immediate action on global warming

Posted on 8 January 2015 by dana1981 &

Lately there seems to have been a shift away from climate science denial, toward arguments downplaying the costs of human-caused climate change. Specifically, some economists publishing reports for Bjorn Lomborg’s Copenhagen Consensus Center have argued that we should focus our efforts more on adapting to climate impacts and on other issues, rather than on cutting carbon pollution and slowing global warming.

According to the Climate Action Tracker, current international climate policies will result in a global surface warming of about 4°C. If we act on all conditional pledges, including those recently made by China and the USA, we’ll see about 3°C warming. This (3–4°C) is the range of global warming that the Copenhagen Consensus Center claims would be the most optimal for the global economy.

One might ask, what sorts of climate impacts would we expect to see as a result of this much global warming? Research indicates that the consequences would be quite severe. For example, widespread coral mortality would occur, and 40–70% of global species would be at risk of extinction. Glacier retreats would threaten water supplies in Central Asia and South America. Sea level rise of 1 meter or more would be expected by 2100, with the possibility of destabilization of the Greenland and West Antarctic ice sheets, which would cause much more sea level rise and flooding of coastal communities.



Time is running out on climate denial

Posted on 30 December 2014 by dana1981 &

From a strictly logical perspective, it’s hard to understand how we can be doing so little to slow global warming. Greg Craven summarized why by examining the extreme possible outcomes in his viral climate ‘decision grid’ video.

In short, if we take action to slow global warming, the worst case scenario involves draconian government regulations that trigger an economic recession. If we don’t, the worst case scenario involves an economic recession too, but also a host of other global and societal catastrophes.

Although Craven doesn’t look at the probabilities of these worst case scenarios, they’re also heavily weighted towards the case for taking action to curb global warming. There are lots of options to slow global warming that don’t involve drastic government regulation, and that can even be beneficial for the economy. If we decide that we’ve gone too far in cutting carbon pollution, it’s relatively easy to scale back government policies.

On the other hand, evidence from past climate change events indicates that triggering tipping points pushing the climate into a dramatically different state is a real possibility. Unlike government policies, as the latest IPCC report noted, many climate change impacts will be irreversible.



Scientists connect the dots from identifying to preventing dangerous climate risks

Posted on 23 December 2014 by dana1981 &

Last week, over 20,000 Earth scientists gathered at the annual American Geophysical Union (AGU) fall conference. They shared their scientific research, ranging from identifying the causes of past climate changes, to estimating the risks of the changes we’re causing now, to how we can successfully communicate the need to mitigate those risks.

Richard Alley (the host of Earth: the Operator’s Manual) summarized the scientific community’s consensus about the threats of abrupt climate change from various potential “tipping points.” Scientists aren’t too worried about a huge methane burp from the ocean or shutdown of the thermohaline circulation (which would cause dramatic cooling in Europe) happening anytime soon. On the other hand, a collapse of the West Antarctic Ice Sheet and large associated sea level rise are becoming increasingly worrying.

This tied into paleoclimate research presented by Aaron Goldner. Atmospheric carbon dioxide levels were at similar levels to today’s (400 parts per million) 15 million years ago during the mid-Miocene period. However, the Earth’s climate was very different. Geologic records give us estimations that sea levels were 25–40 meters higher than today, global mean temperatures 3­–6°C hotter, and there was very little sea ice relative to today.



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.



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