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Call for Emission Limits Heats Debate on Global Warming
by S. Fred Singer
as submitted; printed in edited form in Physics Today, August 1997
The disputed text changes (Physics Today, Aug. 1996) to Chapter 8 of the report of the Intergovernmental Panel on Climate Change (IPCC) [1] point to a possible distortion of science for political purposes. The controversy so far has centered on the changes themselves--their legality, authorship, purpose, and importance. A far more serious problem is that policymakers at the Geneva climate meeting in July 1996 have accepted as a basis for urgent policy action the IPCC's main conclusion, based on Ch. 8, that the "balance of evidence suggests...a discernible human influence on global climate."[2] This innocuous-sounding and nearly self- evident IPCC phrase has been misinterpreted by them to mean that a major climate catastrophe is upon us.
A Ministerial Declaration by the U.S. and like-minded nations was issued on July 18, calling for a protocol to control emissions of carbon dioxide (CO2)--and in effect limit the generation of energy. Such global controls on energy use would have serious economic consequences, impacting mainly on the world's poor.
In announcing this new policy in Geneva, Under Secretary of State Timothy Wirth issued a warning--presumably based on his interpretation of the IPCC report--about regional famine, water shortages, flooding of coastal areas, and the spread of diseases like malaria, yellow fever and cholera.
The revisions to Chapter 8 were made by convening lead author Dr. Benjamin Santer, because of comments received, according to the Physics Today story. This statement obviously calls for considerable amplification. A lead article in the June 13 issue of Nature [3] assigns responsibility to "IPCC officials." There has now surfaced a State Department letter of November 15, 1995, addressed to Sir John Houghton, co-chairman of the IPCC science group, complaining about inconsistencies between the Summary for Policymakers (SPM) and the chapters of the report and advising that it is "essential" that "chapter authors be prevailed upon to modify their text in an appropriate manner following discussion in Madrid."
While the legality of the alterations under IPCC rules is still in dispute, there remain more substantive questions. Did "scientific cleansing" change the sense of the report, as charged by critics? The IPCC says No; Santer charges "willful misinterpretation" of his actions. Nature, while clearly favoring the IPCC and impugning its critics, nevertheless concludes that "there is some evidence that the revision process did result in a subtle shift ... [that] tended to favour arguments that aligned with the report's broad conclusions." The Nature article further admits that "phrases that might have been (mis)interpreted as undermining these conclusions have disappeared".
According to a June 12 Wall Street Journal article by Dr. Frederick Seitz, key phrases deleted from the final draft of Chapter 8 included:
"None of the studies cited above has shown clear evidence that we can attribute the observed [climate] changes to the specific cause of increases in greenhouse gases."
"No study to date has positively attributed all or part [of the climate change observed to date] to anthropogenic [man- made] causes."
"Any claims of positive detection of significant climate change are likely to remain controversial until uncertainties in the total natural variability of the climate system are reduced."
Why were these changes made? Michael MacCracken is quoted by Physics Today: The authors needed to "more clearly express the level of confidence in their results." According to a June 21 Science article [4], Santer "fine-tuned the wording to bring the report into line with the scientific consensus" (emphasis added). IPCC officials quoted by Nature claim the reason for the revisions was "to ensure that it conformed to a `policymakers' summary' of the full report..." Their claim raises the obvious question: Should not a summary conform to the underlying scientific report rather than vice versa? More important, the SPM is a political consensus of government delegations not a scientific one.
Why were IPCC officials so anxious to make the scientific report conform to the Summary? Perhaps because the Summary contains so little to back the political claim of a global warming threat. Ever economical with the truth, the Summary presents the underlying facts selectively and omits relevant information. For example, the Summary does not even mention the existence of 18 years of weather satellite data that show a slight cooling trend [5], contradicting theoretical models of climate warming.
In its earlier 1990 report, the IPCC used the artful phrase that global temperature data and climate models were "broadly consistent." This phrase has now been abandoned. In 1996, the main conclusion seems to be the "discernible human influence on global climate." Nothing new here; we have known for some years that the stratosphere is cooling [6], that the diurnal temperature range has been decreasing [7], that the frequency of hurricanes has been diminishing [8], etc.--most likely as the result of some human influence.
While many scientists would not object to the phrase about "discernible human influence", its ambiguity can mislead others. It is unfortunate that the IPCC Summary juxtaposes the phrase with the results of climate models predicting a temperature rise of between 1 and 3.5 C by 2100. Even if a "discernible human influence" were to exist in the global temperature record, this does not mean that greenhouse warming will occur at anywhere near the rapid rate calculated from current climate models--although this is exactly what many policymakers were led to believe when they read the Summary. Paragraph 2 of the Ministerial Declaration of July 18 specifically--and improperly--links the IPCC phrase about human influence to a temperature increase of 2 C by 2100. In fact, the IPCC conclusion does not validate climate models and should not be used to deduce anything at all about "climate sensitivity."[9]
The Ministerial Declaration is a serious misinterpretation of the IPCC report and of climate science. It will be a test of the scientific integrity of the IPCC to make this fact known to policy makers in no uncertain terms.
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1. IPCC 1996 (The Second Assessment Report of the IPCC): "Climate Change 1995: The Science of Climate Change" J.T. Houghton et al. (eds.), Cambridge University Press, 1996. The UN-sponsored IPCC acts as scientific advisor to the governments adhering to the FCCC signed at the 1992 UN Earth Summit in Rio de Janeiro. Chapter 8 ("Detection of Climate Change and Attribution of Causes") is authored by B.D. Santer (convening lead author), T.M.L. Wigley, T.P. Barnett, and E. Anyamba.
2. This IPCC conclusion seems to be based mainly on two research papers by B.D. Santer et al., (Clim.Dyn. 12, 77-100, 1995 and Nature 382, 39-46, 1996) that were published in Dec. 1995 and July 1996, resp., after the IPCC accepted the final draft report (November 1995), and well after the draft was distributed for comment (April 1995). Chapter 8 contains 19 references to the two papers; eight of Santer's co-authors are listed as contributors to the chapter. The papers claim an "increasing similarity" between observed patterns of global temperature changes and model-simulated responses to a combined sulfate aerosol/CO2 forcing; these claims are being challenged in several communications to scientific journals.
3. "Climate debate must not overheat", Nature 381, 539 (13 June 1996). Trying to marginalize scientific critics, the article refers to "dissent from a dwindling band of skeptics", but some 100 atmospheric scientists have now been willing to sign the Leipzig Declaration , based on a conference held there in November 1995 to discuss critically the evidence for global warming.
4. News & Comments, Science 272, 1734 (1996).
5. R. W. Spencer and J. R. Christy, J. Climate 6, 1194--1204 (1993). Chapter 3 of the IPCC report discusses the satellite data; its Technical Summary allocates them three lines (p. 27); its Policymakers' Summary does not mention satellites. An earlier draft of Chapter 8 mentioned that the satellite data showed a cooling rather than a warming trend; this was later changed to argue that "meaningful interpretations" of satellite data are hard to make because they were not available before 1979.
6. R.W. Spencer and J.R. Christy, J. Climate 5, 847--857 (1992).
7. T.R. Karl et al, Bull.Am.Met.Soc. 74, 1007--1023 (1993).
8. C.W. Landsea et al., Geophys Res Letters, 23, 1697-1700, 1996.
9. Defined as the temperature increase produced by a doubling in the concentration of CO2-equivalent greenhouse gases. Ch. 8 of reference [1] (p. 434) states explicitly: "To date, pattern-based studies have not been able to quantify the magnitude of a greenhouse gas or aerosol effect on climate." |
