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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.

What the science says...

That humans are causing global warming is the position of the Academies of Science from 19 countries plus many scientific organizations that study climate science. More specifically, around 95% of active climate researchers actively publishing climat

Scientists need to back up their opinions with research and data that survive the peer-review process. A survey of all peer-reviewed abstracts on the subject 'global climate change' published between 1993 and 2003 shows that not a single paper rejected the consensus position that global warming is man caused (Oreskes 2004). 75% of the papers agreed with the consensus position while 25% made no comment either way (focused on methods or paleoclimate analysis).

Subsequent research has confirmed this result. A survey of 3146 earth scientists asked the question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009). More than 90% of participants had Ph.D.s, and 7% had master’s degrees. Overall, 82% of the scientists answered yes. However, what are most interesting are responses compared to the level of expertise in climate science. Of scientists who were non-climatologists and didn't publish research, 77% answered yes. In contrast, 97.5% of climatologists who actively publish research on climate change responded yes. As the level of active research and specialization in climate science increases, so does agreement that humans are significantly changing global temperatures.

Figure 1: Response to the survey question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009) General public data come from a 2008 Gallup poll.

Most striking is the divide between expert climate scientists (97.4%) and the general public (58%). The paper concludes:

"It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes. The challenge, rather, appears to be how to effectively communicate this fact to policy makers and to a public that continues to mistakenly perceive debate among scientists."

This overwhelming consensus among climate experts is confirmed by an independent study that surveys all climate scientists who have publicly signed declarations supporting or rejecting the consensus. They find between 97% to 98% of climate experts support the consensus (Anderegg 2010). Moreover, they examine the number of publications by each scientist as a measure of expertise in climate science. They find the average number of publications by unconvinced scientists (eg - skeptics) is around half the number by scientists convinced by the evidence. Not only is there a vast difference in the number of convinced versus unconvinced scientists, there is also a considerable gap in expertise between the two groups.

Figure 2: Distribution of the number of researchers convinced by the evidence of anthropogenic climate change and unconvinced by the evidence with a given number of total climate publications (Anderegg 2010).

Scientific organizations endorsing the consensus

The following scientific organizations endorse the consensus position that "most of the global warming in recent decades can be attributed to human activities":

The Academies of Science from 19 different countries all endorse the consensus. 11 countries have signed a joint statement endorsing the consensus position:

Academia Brasiliera de Ciencias (Brazil)

Royal Society of Canada

Chinese Academy of Sciences

Academie des Sciences (France)

Deutsche Akademie der Naturforscher Leopoldina (Germany)

Indian National Science Academy

Accademia dei Lincei (Italy)

Science Council of Japan

Russian Academy of Sciences

Royal Society (United Kingdom)

National Academy of Sciences (USA) (12 Mar 2009 news release)

"Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science."

African Academy of Sciences

Cameroon Academy of Sciences

Ghana Academy of Arts and Sciences

Kenya National Academy of Sciences

Madagascar's National Academy of Arts, Letters and Sciences

Nigerian Academy of Sciences

l'Académie des Sciences et Techniques du Sénégal

Uganda National Academy of Sciences

Academy of Science of South Africa

Tanzania Academy of Sciences

Zimbabwe Academy of Sciences

Zambia Academy of Sciences

Sudan Academy of Sciences

Two other Academies of Sciences that endorse the consensus:

Updated on 2010-07-25 by John Cook.

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What the science says...

Scientific organizations endorsing the consensus