In 1988, when global warming was becoming a more prominent topic, the World Meteorological Organization (WMO) created the Intergovernmental Panel on Climate Change to assess global warming and its impacts. This organization produces comprehensive Assessment Reports written and reviewed by hundreds of experts around the world based on all relevant articles in peer-reviewed scientific journals. In 1990, the First Assessment Report (FAR) concluded that observed warming "is broadly consistent with predictions of climate models" but "could be largely due to... natural variability." (p. xii). Based on scientific work in the intervening years, the recent Assessment Report Five (AR5) concluded that:

"It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic [human caused] increase in greenhouse gas concentrations and other anthropogenic forcings together" (p. 15).

Statements by the Scientific Community

Statements in support of the key IPCC conclusions have been published by leading scientific societies,including

• American Meteorological Society
• American Geophysical Union
• American Physical Society
• Royal Meteorological Society (United Kingdom)

Some individual scientists, including meteorologists and physicists, argue that humans have a relatively small effect on climate. While these scientists receive great attention in the popular press and in Congress, they seem to be a small minority among climate researchers.

Surveys of scientists in climate-related fields have found high levels of agreement that humans are likely to be causing global warming. For instance, among published members of the American Meteorological Society (Stenhouse et al., 2013),

• 75%: global warming at least about half caused "by human activity",
• 5%: global warming not happening or mostly caused "by natural events",
• 20%: various levels of uncertainty.

A survey of geologists found 82% agreement that "human activity is a significant contributing factor in changing mean global temperatures" (Doran and Kendall Zimmerman, 2009). [See "Near Unanimity?" below for further statistics.]

In conclusion, the main scientific bodies and a large majority of scientists in climate-related fields believe that much of global warming is caused by humans. A small minority disagrees.

Return to front page.

Near Unanimity?

Doran and Kendall Zimmerman (2009) found 97% agreement (that human activity contributes to climate change) among a subset of responses which came from experts in climate change, but the sample size was very small (77 responses, compared to 3146 responses from all specialties). Cook et al. (2013) found that among climate papers they analyzed, 97% of the papers endorsed the idea that humans were causing global warming. This may be an overestimate since the sample included papers about impacts and mitigation of global warming, which generally would take human influence as a premise rather than a topic for investigation.

References

Charney Report: Ad Hoc Study Group on Carbon Dioxide and Climate, 1979: Carbon dioxide and climate: a scientific assessment, report to the Climate Research Board, Assembly of Mathematical and Physical Sciences, National Research Council.

Cook, J., D. Nuccitelli, S. A. Green, M. Richardson, B. Winkler, R. Painting, R. Way, P. Jacobs, and A. Skuce: 2013: Quantifying the consensus on anthropogenic global warming in the scientific literature, Neviron. Res. Lett, 8, doi:10.1088/1748-9326/8/2/024024

Doran, P., and M. Kendall Zimmerman, 2009: Examining the Scientific Consensus on Climate Change, Eos, Trans. Amer. Geophys. Union, 90.

Stenhouse, N., E. Maibach, S. Cobb, R. Ban, A. Bleistein, and P. Croft, 2013: Meteorologists' views about global warming: a survey of American Meteorological Society professional members, Bull. Amer. Meteor. Soc., doi 10.1175/BAMS-D-13-00091.1.

Last modified: 22 July 2018