Established in 1988 by the United Nations Environment Programme, the Intergovernmental Panel on Climate Change (IPCC) is an international scientific body mandated to provide international policy makers, and others, with objective scientific information on Global Climate Change. The IPCC has since provided 4 major “Assessment Reports detailing the state of the scientific knowledge on climate change (1990, 1995, 2001 and 2007), with each assessment including a volume from each of three subject-oriented working groups and a summary for decision makers.

The IPCC does not conduct scientific research, but rather reviews the data collected by other scientific research projects. The 2007 Assessment took 6 years to review the data from over 29,000 separate research projects. The “Climate Change 2007” results were condensed into 3 volumes of approximately 900 pages, and one shorter summary document, by a team of over 1250 lead editors and scientific authors, and reviewed by over 2500 scientific experts from over 130 nations. All reports are available to the public on the internet at www.ipcc.ch.

By its mandate, the IPCC must present decision-makers with conclusions of scientific fact, rather the mere presentation of data. All conclusions presented by the IPCC include a verbal “qualifiers” (“likely”, “very likely”) that represent the consensus of the authors and reviewers. Thus while individual authors or reviewers may agree, or disagree, with a specific conclusion, all must agree about the probably of correctness. In this manner a “consensus of scientific opinion” is reached.

Without doubt the IPCC reviews are one of the largest international scientific endeavors undertaken by mankind, and the IPCC methodology ensures the highest level of scientific creditability. Consequently much of our climate change information is based on these consensus scientific reports. And, when the first conclusion of the Climate Change 2007: Summary for Decisionmakers is: “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level” we might be well advised to accept this conclusion and apply ourselves to reducing our carbon impact and adapting to a new climatic regime.

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Update (3/1/2010):

The last several months has seen a great deal of publicity given to the 2007 IPCC Assessment Reports following the discovery of “errors” that have lead some to question the validity of the reports and thus the creditability of the science underlying global warming.  The situation has now been clarified sufficiently to permit a reasonable evaluation.  To date, two errors have been found and an additional two items can best be described as “sloppiness leading to confusion”.

As described above, the 2007 Assessment Reports were a massive undertaking, involving thousands of scientists from around the world.  These volunteers, participating in one of three “working groups” authored the three reports of the Climate Change 2007 Assessment ( “The Physical Science Basis” (996 pages)⁽¹⁾, “Impacts, Adaption and Vulnerability” (976 pages)⁽²⁾, and “Mitigation of Climate Change” (851 pages)⁽³⁾) and a 104 page “Synthesis Report”⁽⁴⁾ which provides a combined summary of the three scientific Assessment Reports to fulfill the mandate of providing information to “policy makers”, and other interested parties.

All of the four identified issues are contained within “Impacts, Adaption and Vulnerability” report, predominately prepared by social scientists.  (Note:  I have previously mentioned  the relative paucity of needed involvement of the social sciences in the study of climate change.)  No errors, or other issue, have been detected in the other volumes.  It is most significant that no errors have been detected in the  The report “Climate Change 2007: The Physical Science Basis” which presents the basic underlying science of global warming/climate change.  

The most onerous error in the “impacts volume” is a statement which vastly overstates the melting rate of the Himalayan glaciers:

“Glaciers in the Himalaya are receding faster than in any other part of the world (see Table 10.9) and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate. Its total area will likely shrink from the present 500,000 to 100,000 km2 by the year 2035 (WWF, 2005).”

Due to the significance of the Himalayan glaciers as a water source for vast populations, a “high likelihood”  of their rapid disappearance would be of grave concern; and, referencing the World Wildlife Federation (WWF) as the authority for such a conclusion hardly seems appropriate.  In reality, while the data shows that the Himalayan glaciers are clearly retreating at a rate that will result in substantial loss by the end of the century, there is no evidence to make the predictions included in the report.  (Read more in The New York Times.)  It must also be noted that, as this error was not repeated in the summary Synthesis Report (see recent IPCC clarification statement).

The other error was a statement in the chapter on Europe that “55% of the Netherlands is below sea level”; when in fact 26% of the Netherlands is below sea level and 29% is susceptible to flooding.  This misstatement has been attributed to information provided by the Netherlands Environmental Assessment Agency, which has recently provided a correction and clarification.

In the chapter on Africa, the report says that climate change and normal variability could reduce crop yields in northern Africa.  In later discussions the verbiage “normal variability” was omitted, making it appear that climate change would be the sole cause of reduced crop yields in the future.

And finally, the “Impacts” volume reignited a long standing debate between economists regarding the costs of climate change.  The report says that the more extreme weather events are due to global warming and are causing increased costs.  Some feel that it is unclear whether increased costs are due to weather events, or societal behaviors such as building in hazard-prone areas.

In the 3 years since the publication of the 2007 Assessment Reports, which total almost 3,000 total pages in length (exact page count may vary by format and publisher), these are the only issues of questionable accuracy that have arisen.  No errors, typos,  or other issues, have been uncovered in the first volume which presents the basic, underlying science of global warming and climate change.  While regrettable, and sloppy science, It should be readily obvious that these errors and issues have no bearing upon the reality of global warming nor the contributing role of humankind.  However the so-called “climate change deniers” have managed to seize upon these issues, blow them entirely out of proportion and use them as proof that the science of global warming is false, causing inestimable harm.  At a minimum they have so swayed public opinion that it will be vastly more difficult, if not impossible, for political bodies to pass meaningful climate change legislation. 

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1. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp.
2. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.  M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds.  Cambridge University Press, Cambridge, UK, 976 pp.
3. Climate Change 2007: Mitigation of Climate Change.  Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007.  B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds).  Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 851 pp.
4. Climate Change 2007: Synthesis Report.  Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.  Core Writing Team, Pachauri, R.K. and Reisinger, A. (Eds.).  IPCC, Geneva, Switzerland. pp 104.