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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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Explaining climate change science & rebutting global warming misinformation

Scientific skepticism is healthy. Scientists should always challenge themselves to improve their understanding. Yet this isn't what happens with climate change denial. Skeptics vigorously criticise any evidence that supports man-made global warming and yet embrace any argument, op-ed, blog or study that purports to refute global warming. This website gets skeptical about global warming skepticism. Do their arguments have any scientific basis? What does the peer reviewed scientific literature say?


2015 SkS Weekly Digest #4

Posted on 25 January 2015 by John Hartz

SkS Highlights

John Abraham's The oceans are warming so fast, they keep breaking scientists' charts garnered the most comments of the articles posted during the past week. Receiving the second highest number of comments was The Most Terrifying Papers I Read Last Year by Kaitlin Alexander of the ClimateSight blog.

Toon of the Week

2015 Toon 4 

H/t to I Heart Climate Scientists.



2015 SkS Weekly News Roundup #4B

Posted on 24 January 2015 by John Hartz

AfDB Climate Change Committee shares outcomes of COP20 and looks ahead to Paris climate talks

On Wednesday, January 21, the African Development Bank’s Climate Change Coordination Committee (CCCC) organized a knowledge sharing seminar at the institution’s headquarters in Abidjan to highlight the outcomes of the 20th Conference of Parties (COP20) to the United Nations Framework Convention on Climate Change in Lima, Peru, in December. The committee also looked ahead to COP21 in Paris later this year, where a new universally binding climate agreement is expected to be concluded. 

In his opening remarks, Solomon Asamoah, Vice-President, Infrastructure, Private Sector and Regional Integration, explained why the climate debate is important for Africa: “Africa is our workplace and our home; if its concerns are not part of the global climate debate; our business suffers. But it’s not just the business; it’s the millions of lives and livelihoods at stake. This should matter to us”. Asamoah was quick to caution that the Bank cannot manage this task alone and called for the Bank to develop meaningful partnerships with other institutions around the world.

COP20 presented Africa with the opportunity to examine the implications of the proposed new and binding international agreement on the continent and the imperative of Africa’s leaders to prepare to take on binding commitments as being proposed and to grow low-carbon and climate-resilient economies.

AfDB Climate Change Committee shares outcomes of COP20 and looks ahead to Paris climate talks, African Development Bank, Jan 22, 2015



The Most Terrifying Papers I Read Last Year

Posted on 23 January 2015 by Guest Author

An ice sheet forms when snow falls on land, compacts into ice, and forms a system of interconnected glaciers which gradually flow downhill like play-dough. In Antarctica, it is so cold that the ice flows right into the ocean before it melts, sometimes hundreds of kilometres from the coast. These giant slabs of ice, floating on the ocean while still attached to the continent, are called ice shelves.

For an ice sheet to have constant size, the mass of ice added from snowfall must equal the mass lost due to melting and calving (when icebergs break off). Since this ice loss mainly occurs at the edges, the rate of ice loss will depend on how fast glaciers can flow towards the edges.

Ice shelves slow down this flow. They hold back the glaciers behind them in what is known as the “buttressing effect”. If the ice shelves were smaller, the glaciers would flow much faster towards the ocean, melting and calving more ice than snowfall inland could replace. This situation is called a “negative mass balance”, which leads directly to global sea level rise.

Photo by Tas van Ommen

Respect the ice shelves. They are holding back disaster.

Ice shelves are perhaps the most important part of the Antarctic ice sheet for its overall stability. Unfortunately, they are also the part of the ice sheet most at risk. This is because they are the only bits touching the ocean. And the Antarctic ice sheet is not directly threatened by a warming atmosphere – it is threatened by a warming ocean.

The atmosphere would have to warm outrageously in order to melt the Antarctic ice sheet from the top down. Snowfall tends to be heaviest when temperatures are just below 0°C, but temperatures at the South Pole rarely go above -20°C, even in the summer. So atmospheric warming will likely lead to a slight increase in snowfall over Antarctica, adding to the mass of the ice sheet. Unfortunately, the ocean is warming at the same time. And a slightly warmer ocean will be very good at melting Antarctica from the bottom up.



2015 SkS Weekly News Roundup #4A

Posted on 22 January 2015 by John Hartz

Al Gore: oil companies 'use our atmosphere as an open sewer'

It’s not possible to listen to petroleum industry executives defending their reckless extraction of oil without feeling that we are living in an age of madness.

In a recent private conversation under the Chatham House rule, one of the world’s most senior industry leaders, who is considered to be at the more moderate end of the spectrum, insisted that we are going to burn all the world’s hydrocarbons despite the consequences.

His reasoning is that a growing population in the developing world needs energy to raise living standards, that renewables will not become a dominant energy source till the end of the century and that politicians don’t have the courage or power to limit production.

He acknowledged that the burning of all reserves would almost certainly lead to temperature rises of up to 4C, but argued the best way forward is to focus on limiting the damage through such technologies as carbon capture and storage.

Al Gore: oil companies 'use our atmosphere as an open sewer' by Jo Confino, The Guardian, Jan 21, 2015



The oceans are warming so fast, they keep breaking scientists' charts

Posted on 22 January 2015 by John Abraham

Ocean heat content data to a depth of 2,000 meters, from NOAA.

Ocean heat content data to a depth of 2,000 meters, from NOAA.

Wow, was this a bad year for those who deny the reality and the significance of human-induced climate change. Of course, there were the recent flurry of reports that 2014 surface temperatures had hit their hottest values ever recorded. The 2014 record was first called on this blog in December and the final results were reported as well, here. All of this happened in a year that the denialists told us would not be very hot. 

But those denialists are having a tough time now as they look around the planet for ANY evidence that climate change is not happening. The problem is, they’ve been striking out.



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,



2015 SkS Weekly Digest #3

Posted on 20 January 2015 by John Hartz

SkS Highlights

Dana's Global warming made 2014 a record hot year – in animated graphics received the highest number of comments of the articles posted on SkS during the past week.

Comments Policy Update

The SkS Comments Policy was amended with the addition of the following sentence. 

Moderation complaints are always off topic and will be deleted.

El Niño Watch

There has been a lot of buzz over the last few months of an El Nino taking shape across the globe. These often bring wet conditions to the southern and western U.S. and warmer conditions to the state of Minnesota. But recent observations are showing that our El Nino may not even happen. 

There are many different ways to measure if an El Nino is occurring, but the main way is to measure sea surface temperatures in the equatorial Pacific… it's this area that is often most affected by an El Nino event. Well, the latest trends aren't promising…

Our El Nino year may not happen by Cody Matz KMSP (Detroit), Jan 18, 2015 

As colder than seasonal temperatures have taken hold across Canada this winter, you may be asking, “Where is El Niño?” The answer is that El Niño conditions are already in place in the Pacific, but not all El Niños are created equal. Analysis of current conditions shows how this year’s unique flavour of El Niño will help keep some parts of Canada warm, while others will remain in the deep freeze.

El Niño update explains impact on Canada in months to come by Michael Carter, The Weather Newtwork, Jan 16, 2015 

Toon of the Week

 2015 Toon 3



Call to climate scientists: submit your quote for 97 Hours of Consensus 2015

Posted on 19 January 2015 by John Cook

On 7 September 2014, we launched 97 Hours of Consensus. Every hour for 97 consecutive hours, we published a cartoon of a climate scientist with a quote about climate change. We also published a very cool interactive webpage. Our purpose: to raise awareness of the scientific consensus on human-caused global warming.

The series was an amazing success. We reached millions of people through social and mainstream media, including President Obama tweeting about 97 hours to 43 million followers:

On 7 September 2015, we're repeating 97 Hours of Consensus with another 97 climate scientists. But with a different approach. This time, we're asking climate scientists to submit their quotes to us. So this is my call to action to the climate science community. If you're a climate scientist who:

  • has something to say about the issue of human-caused global warming,
  • and is interested in your words reaching millions of people,
  • and would like to be drawn in cartoon form

then submit your quote in our 97 Hours of Consensus Submission Form.



2015 SkS Weekly News Roundup #3B

Posted on 17 January 2015 by John Hartz

2014 breaks heat record, challenging global warming skeptics

Last year was the hottest on earth since record-keeping began in 1880, scientists reported on Friday, underscoring warnings about the risks of runaway greenhouse-gas emissions and undermining claims by climate-change contrarians that global warming had somehow stopped.

Extreme heat blanketed Alaska and much of the Western United States last year. Records were set across large areas of every inhabited continent. And the ocean surface was unusually warm virtually everywhere except near Antarctica, the scientists said, providing the energy that fueled damaging Pacific storms.

In the annals of climatology, 2014 surpassed 2010 as the warmest year. The 10 warmest years have all occurred since 1997, a reflection of the relentless planetary warming that scientists say is a consequence of human activity and poses profound long-term risks to civilization and nature.

2014 breaks heat record, challenging global warming skeptics by Justin Gillis, New York Times, Jan 16, 2015



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



Uncertainty, sensitivity and policy: Kevin Cowtan's AGU presentation

Posted on 15 January 2015 by Kevin C

The surface thermometer record forms a key part of our knowledge of the climate system. However it is easy to overlook the complexities involved in creating an accurate global temperature record from historical thermometer readings. If the limitations of the thermometer record are not understood, we can easily draw the wrong conclusions. I reevaluated a well known climate sensitivity calculation and found some new sources of uncertainty, one of which surprised me.
This highlights two important issues. Firstly the thermometer record (while much simpler than the satellite record) requires significant expertise in its use - although further work from the record providers may help to some extent. Secondly, the policy discussion, which has been centered on the so called 'warming hiatus', has been largely dictated by the misinformation context, rather than by the science.

At the AGU fall meeting I gave a talk on some of our work on biases in the instrumental temperature record, with a case study on the implications from a policy context. The first part of the talk was a review of our previous work on biases in the HadCRUT4 and GISTEMP temperature records, which I won't repeat here. I briefly discussed the issues of model-data comparison in the context of the CMIP-5 simulations, and then looked at a simple case study on the application of our results.

The aim of doing a case study using our data was to ascertain whether our work had any implications beyond the problem of obtaining unbiased global temperature estimates. In fact repeating an existing climate sensitivity study revealed a number of surprising issues:

  1. Climate sensitivity is affected by features of the temperature data which were not available to the original authors.
  2. It is also affected by features of the temperature record which we hadn't considered either, such as the impact of 19th century ship design.
  3. The policy implications of our work have little or nothing to do with the hiatus.

The results highlight the fact that significant expertise is currently required to draw valid conclusions from the thermometer record. This represents a challenge to both providers and users of temperature data.


Let's start by looking at the current version of our temperature reconstruction, created by separate infilling of the Hadley/CRU land and ocean data. The notable differences are that our reconstruction is warmer in the 2000's (due to rapid arctic coverage), and around 1940, and cooler in the 19th century due to poor coverage in HadCRUT4 (figure 1).

 Figure 1: Cowtan and Way version 2 infilled temperature series

Figure 1: Comparison of the Cowtan and Way version 2 long reconstruction against HadCRUT4, showing the uncertainty interval from CWv2.



The Antarctic ice sheet is a sleeping giant, beginning to stir

Posted on 14 January 2015 by John Abraham

In a paper I just published with colleague Dr. Ted Scambos from the National Snow and Ice Data Center, we highlight the impact of southern ice sheet loss, particularly the West Antarctic Ice Sheet on sea-level rise around the world.

We know that human emissions of greenhouse gases are causing the Earth’s temperature to rise and are creating other changes across the Earth’s climate system. One change that gets a great deal of attention is the current and future rates of sea-level rise. A rising sea level affects coastal communities around the world; approximately 150 million people live within 1 meter of current sea level.

The waters are rising because of a number of factors. First, water expands as it warms. In the past, this “thermal expansion” was the largest source of sea-level rise. But as the Earth’s temperatures continued to increase, another factor (melting ice, particularly from large ice sheets in Greenland and Antarctica) has played an ever increasing role.

In the Southern Hemisphere, the largest player is the Western Antarctic Ice Sheet (WAIS). It is less stable than Eastern Antarctica and is particularly vulnerable to melting from below by warmed ocean waters. Scientists are closely watching the ice near the edges of the WAIS because they buttress large volumes of ice that are more inland. When these buttressing ice shelves melt, the ice upstream will slide more rapidly toward the ocean waters. 

As reported in our paper, according to some studies, “no further acceleration of climate change and only modest extrapolations of the current increasing mass loss rate are necessary for the system to eventually collapse ... resulting in 1-3 m of sea-level rise.” And this is from just one component of the great southern sheets.



2015 SkS Weekly News Roundup #3A

Posted on 13 January 2015 by John Hartz

2015 begins with CO2 above 400 PPM mark

The new year has only just begun, but we’ve already recorded our first days with average carbon dioxide levels above 400 parts per million, potentially leading to many months in a row above this threshold, experts say.

The Scripps Institution of Oceanography records of atmospheric carbon dioxide levels show that Jan. 1 was the first day of the new year above that concentration, followed by Jan. 3 and Jan. 7. Daily averages have continued at this level or higher through Jan. 9, though they could continue to dance up and down around that mark due to day-to-day variations caused by weather systems. But even with those fluctuations, 2015 will likely see many months above 400 ppm, possibly starting with the very first month of the year.

“My guess at this point is that January 2015 will be very slightly above 400 ppm, but it's too early to tell for sure,” Ralph Keeling, the scientist in charge of the CO2 monitoring project atop Hawaii’s Mauna Loa, said in an email. Keeling’s father, Charles, began the project in 1958. The graph that shows the decades-long rise in CO2 is eponymously called the Keeling Curve.

2015 Begins With CO2 Above 400 PPM Mark by Andrea Thompson, Climate Central, Jan 12, 2015



Just when did humans first start affecting the climate?

Posted on 13 January 2015 by howardlee


Homo incendius – “fire man” – is an informal nickname for our ancestors who first learned how to make fire. As one of the quintessential human attributes, you might expect fire-making to have arisen along with our own species, Homo sapiens when we emerged in Africa some 208,000 years ago.


You have to go much further back in time, before Neanderthals and even before the earlier Homo heidelbergensis. The first solid evidence for our ancestors’ regular use of fire dates to 1 million years ago, and possibly as far back as 1.5 million years ago. That’s during the reign of Homo erectus – our first fire-making, food-cooking, big-game-hunting, art-making, intercontinental-travelling ancestor.

 Homo erectus (Peking Man)

Homo erectus a.k.a. Homo incendius (Source: Cicero Moraes - via Wikimedia Commons)

Homo erectus took fire-making skills to the Levant and all the way to China by about 770,000 years ago, but strangely our contemporary ancestors who traveled to the fringes of the ice sheets in Europe don’t seem to have been habitual fire-users until much later - about 400,000 years ago.



Corrosive Seawater, Not Low pH, Implicated As Cause of Oyster Deaths

Posted on 12 January 2015 by Rob Painting

Key Points:
  • Because of the geologically-rapid emission of carbon dioxide into the atmosphere by human industrial activities, and the subsequent dissolution of this CO2 into the global oceans, ocean pH and carbonate saturation state are currently declining in tandem - a process known as ocean acidification.
  • Over geological timescales, however, ocean pH and carbonate saturation (corrosiveness) tend to become disassociated. This explains why the ancient oceans were highly saturated with carbonates and therefore conducive to calcification (calcium carbonate shell formation) at times of high CO2 in Earth's past even though ocean pH was lower than it is today. 
  • Waldbusser et al (2014) conducted a series of experiments with oyster and mussel juvenile life stages (larvae) which enable them to distinguish between the individual responses to carbonate saturation and ocean pH, something not done in typical ocean acidification laboratory experiments
  • The authors surprisingly found that, except at extremely low concentrations, ocean pH by itself had little impact on larvae growth. As expected though, low carbonate saturation was very detrimental to larvae growth and thus survival. This work implicates carbonate undersaturation as the key mechanism responsible for the large-scale die-off of oyster larvae along the North American Pacific coastline over the last decade.

Figure 1 - Images of the ancient fossil calcifier Discoaster before (left) and during (right) the Paleocene-Eocene Thermal Maximum (PETM) about 56 million years ago. Both creatures lived at times when the atmospheric concentration of CO2 was much higher than present-day and ocean pH was lower, but the fossil in the right-hand image lived when carbonate ion abundance (and carbonate saturation) was also low. This was due to a rapid increase in atmospheric CO2, which caused seawater to become corrosive to calcium carbonate forms. Image courtesy of Professor Patrizia Ziveri.



2015 SkS Weekly Digest #2

Posted on 11 January 2015 by John Hartz

SkS Highlights

Not pHraud but pHoolishness, a guest post by Richard Telford attracted the most comments of the articles posted on SkS during the past week. Another guest post, Climate Deniers Employ Predatory Tactics in Fight Against Facts: Scientist by Deirdre Fulton attracted the second highest number of comments. 

Be sure to check out our new featureMedia Matters Posts about Environment & Science 

El Niño Watch

Japan's weather bureau said on Friday the El Nino weather pattern, often linked to both heavy rainfall and drought, is continuing but added that the phenomena could end over spring.

The Japan Meteorological Agency forecast said the El Nino, which emerged during last summer for the first time in five years, was already starting to ease.

El Nino likely to head to an end over spring: Japan weather bureau, Reuters, Jan 9, 2015 

Toon of the Week

2015 Toon 2 



2015 SkS Weekly News Roundup #2B

Posted on 10 January 2015 by John Hartz

Brazil’s former Sports Minister is moved to science post despite rejection of global warming science

For the president in any democracy, compromises are often necessary in assembling a cabinet that satisfies a range of constituencies. But even with that in mind, it’s really hard to understand how President Dilma Rousseff of Brazil, who has repeatedly pressed for strong global action to curb climate change, could possibly justify her choice of Aldo Rebelo as her new minister of science, technology and innovation.

It’s unfortunate that Rebelo has no scientific background and probably didn’t absorb many relevant insights in the position he held since 2011 — minister of sports. But that’s a minor issue compared to his attacks on even the most basicestablished aspects of science pointing to human-driven global warming.

To get a feel for his views, which put the longtime Communist Party legislator in line with Tea Party talking points, start with the blistering critique of the appointment by Steve Schwartzman of the Environmental Defense Fund, who’s been immersed in Brazilian environmental and forest science and politics for decades.  

Brazil’s Former Sports Minister is Moved to Science Post Despite Rejection of Global Warming Science by Andrew Revkin, Dot Earth, New York Times, Jan 7, 2015



Climate Deniers Employ Predatory Tactics in Fight Against Facts: Scientist

Posted on 9 January 2015 by Guest Author

Climate Deniers Employ Predatory Tactics in Fight Against Facts: Scientist by Deirdre Fulton was originally posted on Common Dreams on Jan 6, 2015.

Michael Mann writes that the strategy 'is similar to what happens when a group of lions on the Serengeti seek out a vulnerable individual zebra at the edge of a herd.'

Serengeti lion and zebras

"The 'Serengeti strategy' is often employed wherever there is a strong and widespread consensus among the world’s scientists about the underlying cold, hard facts of a field, whether the subject be evolution, ozone depletion, the environmental impacts of DDT, the health effects of smoking, or human-caused climate change," Mann writes. (Photo: Bulletin of Atomic Scientists/Brocken Inaglory)

Like lions targeting lone zebras in the Serengeti grasslands, industry-backed climate change deniers prefer to target individual scientists rather than take on an entire scientific field at once, climatologist Michael Mann writes in a paper published this month in the Bulletin of the Atomic Scientists.

In "The Serengeti Strategy: How Special Interests Try to Intimidate Scientists, and How Best to Fight Back," Mann describes a concerted effort on the part of fossil fuel interests who find themselves facing overwhelming scientific consensus about the threat of human-caused climate change—and, by implication, the necessity to reduce global carbon emissions.

"By singling out a sole scientist, it is possible for the forces of 'anti-science' to bring many more resources to bear on one individual, exerting enormous pressure from multiple directions at once, making defense difficult," writes Mann, director of the Earth System Science Center at Pennsylvania State University. "It is similar to what happens when a group of lions on the Serengeti seek out a vulnerable individual zebra at the edge of a herd."

Unfortunately, the strategy is effective, he says, which is why similar tactics have been employed by the chemical and pharmaceutical industries, big agriculture, and "just about any corporate interest that has found itself on a collision course with scientific research—particularly research that reveals specific potential damages or threats caused by their product."



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.



2015 SkS Weekly News Roundup #2A

Posted on 7 January 2015 by John Hartz

7 trends that will affect the Planet in 2015

Here are some trends and expected events in 2015 and beyond that may have a significant impact upon the planet and life on Earth.

7 trends that will affect the Planet in 2015 by Parick J. Kiger, Discovery News, Jan 5, 2015



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