<div>At the web links below are an article from the American Institute of Physics on the physics of CO2 in the atmosphere as a greenhouse gas, tracing the history of the science on this subject dating from 1896, a statement from numerous national academies of science around the world who signed the document at the pdf link (Brazil, Canada, China, France, Germany, Italy, India, Japan, Mexico, Russia, United Kingdom, United States, South Africa), and the results of a survey of scientists on their professional evaluation of the claim that human activity is altering climate, compared to public opinion on this issue, followed by an earlier survey of the science on this issue:<br>
<br>Paper from the American Institute of Physics on climate science at URL below:</div>
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<div><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.aip.org/history/climate/co2.htm" target="_blank">http://www.aip.org/history/climate/co2.htm</a></div>
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<div><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.nationalacademies.org/includes/G8Statement_Energy_07_May.pdf" target="_blank">http://www.nationalacademies.org/includes/G8Statement_Energy_07_May.pdf</a></div>
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<div>This article from EOS ('<em>Examining the Scientific consensus on Climate Change</em>', <strong>Volume 90</strong>, Number 3, 2009, available to American Geophysical Union members) which is quoted by Realclimate.org lower down and is available to the public at the website first below, claims that only 58 percent of the public in the US thinks that human activity is a significant contributing factor in changing the mean <span name="st">global</span> temperature, as opposed to 97% of specialists surveyed. This is a very recent effort to quantify the scientific consensus on the validity of anthropogenic climate change and contrast this consensus with public opinion:</div>
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<div><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://tigger.uic.edu/~pdoran/012009_Doran_final.pdf" target="_blank">http://tigger.uic.edu/~pdoran/012009_Doran_final.pdf</a></div>
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<div>Below is another earlier effort to quantify the scientific consensus on climate change, that is mentioned in the <span name="st">survey</span> results from the Peter Doran et. al. effort above, as perhaps not being comprehensive enough:</div>
<div> <br><a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/1686" target="_blank"><font size="2">http://www.sciencemag.org/cgi/content/full/306/5702/1686</font></a><br>
<br><b><font size="2">BEYOND THE IVORY TOWER:</font></b><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="3"><br>The Scientific Consensus on Climate Change<br><br></font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">Naomi Oreskes<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#affiliation" target="_blank">*</a><br>
</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2"><b><br>P</b>olicy-makers and the media, particularly in the United States, frequently assert that climate science is highly uncertain. Some have used this as an argument against adopting strong measures to reduce greenhouse gas emissions. For example, while discussing a major U.S. Environmental Protection Agency report on the risks of climate change, then-EPA administrator Christine Whitman argued, "As [the report] went through review, there was less consensus on the science and conclusions on climate change" (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref1" target="_blank"><span></span> 1</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">. Some corporations whose revenues might be adversely affected by controls on carbon dioxide emissions have also alleged major uncertainties in the science (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref2" target="_blank">2</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">. Such statements suggest that there might be substantive disagreement in the scientific community about the reality of anthropogenic climate change. This is not the case.<br>
<br>The scientific consensus is clearly expressed in the reports of the Intergovernmental Panel on Climate Change (IPCC). Created in 1988 by the World Meteorological Organization and the United Nations Environmental Programme, IPCC's purpose is to evaluate the state of climate science as a basis for informed policy action, primarily on the basis of peer-reviewed and published scientific literature (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref3" target="_blank">3</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">. In its most recent assessment, IPCC states unequivocally that the consensus of scientific opinion is that Earth's climate is being affected by human activities: "Human activities ... are modifying the concentration of atmospheric constituents ... that absorb or scatter radiant energy. ... [M]ost of the observed <span name="st">warming</span> over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations" [p. 21 in (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref4" target="_blank">4</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">].<br>
<br>IPCC is not alone in its conclusions. In recent years, all major scientific bodies in the United States whose members' expertise bears directly on the matter have issued similar statements. For example, the National Academy of Sciences report, Climate Change Science: An Analysis of Some Key Questions, begins: "Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise" [p. 1 in (<span></span> <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref5" target="_blank">5</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">]. The report explicitly asks whether the IPCC assessment is a fair summary of professional scientific thinking, and answers yes: "The IPCC's conclusion that most of the observed <span name="st">warming</span> of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue" [p. 3 in (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref5" target="_blank">5</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">].<br>
<br>Others agree. The American Meteorological Society (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref6" target="_blank">6</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">, the American Geophysical Union (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref7" target="_blank">7</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">, and the American Association for the Advancement of Science (AAAS) all have issued statements in recent years concluding that the evidence for human modification of climate is compelling (<a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref8" target="_blank">8</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">.<br>
<br>The drafting of such reports and statements involves many opportunities for comment, criticism, and revision, and it is not likely that they would diverge greatly from the opinions of the societies' members. Nevertheless, they might downplay legitimate dissenting opinions. That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords "climate change" (<span></span> <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.sciencemag.org/cgi/content/full/306/5702/#ref9" target="_blank">9</a>)</font><font lang="0" style="BACKGROUND-COLOR: #ffffff" face="Arial" color="#000000" size="2">.<br>
<br>The 928 papers were divided into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Of all the papers, 75% fell into the first three categories, either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, taking no position on current anthropogenic climate change. Remarkably, none of the papers disagreed with the consensus position.<br>
<br>Admittedly, authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point.<br><br>This analysis shows that scientists publishing in the peer-reviewed literature agree with IPCC, the National Academy of Sciences, and the public statements of their professional societies. Politicians, economists, journalists, and others may have the impression of confusion, disagreement, or discord among climate scientists, but that impression is incorrect.<br>
<br>The scientific consensus might, of course, be wrong. If the history of science teaches anything, it is humility, and no one can be faulted for failing to act on what is not known. But our grandchildren will surely blame us if they find that we understood the reality of anthropogenic climate change and failed to do anything about it.<br>
<br>Many details about climate interactions are not well understood, and there are ample grounds for continued research to provide a better basis for understanding climate dynamics. The question of what to do about climate change is also still open. But there is a scientific consensus on the reality of anthropogenic climate change. Climate scientists have repeatedly tried to make this clear. It is time for the rest of us to listen.<span></span> <br>
<br><b>References and Notes</b><br><br>1. A. C. Revkin, K. Q. Seelye, New York Times, 19 June 2003, A1. <br><br>2. S. van den Hove, M. Le Menestrel, H.-C. de Bettignies, Climate Policy <b>2</b> (1), 3 (2003). <br><br>3. See <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.ipcc.ch/about/about.htm" target="_blank">www.ipcc.ch/about/about.htm</a>. <br>
<br>4. J. J. McCarthy et al., Eds., Climate Change 2001: Impacts, Adaptation, and Vulnerability (Cambridge Univ. Press, Cambridge, 2001). <br><br>5. National Academy of Sciences Committee on the Science of Climate Change, Climate Change Science: An Analysis of Some Key Questions (National Academy Press, Washington, DC, 2001). <br>
<br>6. American Meteorological Society, Bull. Am. Meteorol. Soc. <b>84</b>, 508 (2003). <br><br>7. American Geophysical Union, Eos <b>84 </b>(51), 574 (2003). <br><br>8. See <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://www.ourplanet.com/aaas/pages/atmos02.html" target="_blank">www.ourplanet.com/aaas/pages/atmos02.html</a>. <br>
<br>9. The first year for which the database consistently published abstracts was 1993. Some abstracts were deleted from our analysis because, although the authors had put "climate change" in their key words, the paper was not about climate change. <br>
<br>10. This essay is excerpted from the 2004 George Sarton Memorial Lecture, "Consensus in science: How do we know we're not wrong," presented at the AAAS meeting on 13 February 2004. I am grateful to AAAS and the History of Science Society for their support of this lectureship; to my research assistants S. Luis and G. Law; and to D. C. Agnew, K. Belitz, J. R. Fleming, M. T. Greene, H. Leifert, and R. C. J. Somerville for helpful discussions. <br>
<br>10.1126/science.1103618 <br>------------------------------------------<br><br></font></div></div><span><span>
<div>Vision2020 Post: Ted Moffett</div></span></span></div>