Richard Lindzen1940) is an atmospheric physicist and a professor of meteorology at MIT renowned for his research in dynamic meteorology, especially atmospheric waves. He is a member of the National Academy of Sciences and held positions at the University of Chicago, Harvard University, and MIT. He was a lead author of Chapter 7  of the IPCC Third Annual Report. He frequently speaks out against the IPCC position that significant global warming is caused by humans (see anthropogenic global warming).
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2 Wall Street Journal 2001
3 IPCC Policymakers Summary criticism
4 Letter to his town mayor, 2003
National Academy of Sciences panel
Lindzen served on an 11-member panel  organized by the National Academy of Sciences. The panel's report, titled Climate Change Science: An Analysis of Some Key Questions, has been widely cited as evidence that leading scientists believe in global warming.
Indeed, the first paragraph of the report summary states,
"Greenhouse gases are accumulated in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability."
Wall Street Journal 2001
Subsequently, however, Lindzen wrote an article for the Wall Street Journal  (June 11, 2001), which insisted that "there is no consensus, unanimous or otherwise, about long-term climate trends or what causes them" and "we are not in a position to confidently attribute past climate change to carbon dioxide or to forecast what the climate will be in the future."
Indeed, he pointed out
"As usual, far too much public attention was paid to the hastily prepared summary rather than to the body of the report. The summary began with a zinger -- that greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise, etc., before following with the necessary qualifications. For example, the full text noted that 20 years was too short a period for estimating long-term trends, but the summary forgot to mention this."
However, while the full text does warn that 20 years is too short to estimate long term trends, this does not qualify their statement about greenhouse gases causing warming as Lindzen implies. In fact, it is a warning about the satellite data, which at the time the report was written did not show much warming. Here is the context in which the warning about long-term trends occurred:
Although warming at Earth's surface has been quite pronounced during the past few decades, satellite measurements beginning in 1979 indicate relatively little warming of air temperature in the troposphere. The committee concurs with the findings of a recent National Research Council report, which concluded that the observed difference between surface and tropospheric temperature trends during the past 20 years is probably real, as well as its cautionary statement to the effect that temperature trends based on such short periods of record, with arbitrary start and end points, are not necessarily indicative of the long-term behavior of the climate system.
Lindzen worked on IPCC Working Group 1, Chapter 7, which is the section which considers the physical processes that are active in real world climate. Lindzen stated in May 2001  that
the IPCC summary does not support the full document: see IPCC. Lindzen further criticized the IPCC for alterations to the Policymakers Summary of its 2001 global warming report, saying:
IPCC Policymakers Summary criticism
Editorial note: The "30 years" period begins at 1970, near the start of the warming trend. The IPCC Shanghai version's "50 years" period of "observed warming" begins in the midst of the 1945-1975 cooling period before the warming trend.
Lindzen worked on IPCC Working Group 1, Chapter 7, which is the section which considers the physical processes that are active in real world climate. Lindzen stated in May 2001  that the IPCC summary does not support the full document: see IPCC. Lindzen further criticized the IPCC for alterations to the Policymakers Summary of its 2001 global warming report, saying:
However, the NAS panel on which Lindzen served (see above) said :
- "The committee finds that the full IPCC Working Group I (WGI) report is an admirable summary of research activities in climate science, and the full report is adequately summarized in the Technical Summary. The full WGI report and its Technical Summary are not specifically directed at policy. The Summary for Policymakers reflects less emphasis on communicating the basis for uncertainty and a stronger emphasis on areas of major concern associated with human-induced climate change. This change in emphasis appears to be the result of a summary process in which scientists work with policy makers on the document. Written responses from U.S. coordinating and lead scientific authors to the committee indicate, however, that (a) no changes were made without the consent of the convening lead authors (this group represents a fraction of the lead and contributing authors) and (b) most changes that did occur lacked significant impact."
Letter to his town mayor, 2003
In September 2003 Lindzen wrote an open letter to his town mayor , putting his opinions on global warming. He says "...the temperature rise seen so far is much less(by a factor of 2-3) than models predict...". This statement is, however, false according to the most accepted climate models used by the IPCC  or see climate model for more in depth information.