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Testimony of Patrick J. Michaels, Department of Environmental Sciences, University of Virginia to the Subcommittee on Energy and the Environment, U. S. House of Representatives, November 16, 1995. This testimony represents the no offfical position of the University or Commonwealth of Virginia.

My testimony centers around four issues of critical importance to the problem of global warming:

1. New calculations support the view of the scientists who predicted that global warming would be relatively modest.

2. Older calculations that based the 1992 Framework Convention on Climate Change were known to be greatly overestimating warming at the time the Convention was ratified.

3.

Critical scientists are still being denied data (by taxpayer-supported organizations) that are required to quantitatively review new syntheses on global warming.

4. Therefore, any studies of the impact of climate change on ecosystems, health, and the economy, based upon older models, are in error, and newer models have yet to be properly reviewed.

Controversy surrounding the issue of global warming caused by an enhancing greenhouse effect is a classic example of the normal and creative scientific tension that exists between those who formulate hypotheses (i.e. "models") and those who evaluate such hypotheses with observed data. If this issue had not been politicized before the hypotheses and observations could naturally converge, global warming would just be another interesting example of applied physical science.

Unfortunately, that is not the case. For the last decade, a community of scientists, often referred to as a "small minority", had argued, based on the observed data on climate change, that the modelled warming was far too large, and therefore that any intrusive policy would not be based upon reliable models of global warming. This view, generated only by data, has been cast in a very negative political light, which has had a chilling effect on scientific free speech. At the same time, testimony has been repeatedly given before the

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U.S. Congress that the observed and modelled temperatures are "broadly consistent". In terms of federal funding, this view has been amply rewarded. But, the two views have never been reconciled scientifically. In fact, while models suggest a warming of roughly 4°C for doubling atmospheric carbon dioxide, the data suggested a much lower number, or approximately 1.0-1.5°C of additional warming.

The most important development in the last two years is that it is now acknowledged that the community that argued for the lower numbers appears more likely to be correct. Moreover, it is apparent that the climate model most heavily cited by the United Nations in its 1992 "Supplementary Report" on Climate Change, prepared specifically to provide technical backing for the Framework Convention on Climate Change, was known to be making large errors in its forecast of present temperature at the time of the adoption of the Framework Convention, and yet this was never entered into the debate concerning the Convention by the community that developed the models.

This observation argues strongly that the scientific review process that bases such international agreements has been flawed. Alternatively, there may have been omissions in communicating to responsible individuals how large the errors in these calculations were.

In a recent paper in the Journal of Climate, J.F.B Mitchell et al. examined a climate model that was very similar to what was heavily cited by the United Nations in 1992. They found that such models predict that the atmosphere should have already warmed between 1.3 and 2.3°C as a result of changes in greenhouse gases; the observed warming is 0.5°C.

As a graphic example of this, note the difference between the greenhouse warming model of Manabe et al. (1991), which was heavily cited by the U.N. in 1992, and observed temperatures as sensed by satellite (Figure 1). The only assumptions used in calculating this difference are that the climate model is correctly estimating the temperature before the greenhouse effect had changed, and that the satellite is correctly measuring the temperature of the lower atmosphere. Comparision of balloon-measured temperatures with the satellite data ensures that this is the case.

Figure two shows an additional comparison between the same model and ground-measured temperatures over the last hundred years in the Northern Hemisphere. An earlier version of this plot appeared in Bulletin of the American Meteorological Society (Michaels and Stooksbury, 1992), prior to ratification of the Framework Convention.

The 1995 "Second Scientific Assessment" of the U.N. Intergovernmental Panel on Climate Change (IPCC) now states that the climate models that supported the 1992 Supplementary Report were in fact predicting too much warming. Rather, it states that the model that best tracks the past climate is one which includes the compensating effects of sulfate aerosols. This model was published by Mitchell et al. in Nature on August 10.

Mitchell et al. state at the outset that models similar to those that based the Framework Convention "have produced a larger mean warming than has been observed", an admission

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Figure 1. Satellite-sensed lower tropospheric temperature vs. surface temperature in the coupled ocean-atmosphere transient model of Manabe et al. (1991), for the period January. 1979 (When the satellite record begins), through October, 1995. Top: Northern Hemisphere; Bottom: Southern Hemisphere.

that those who claimed this over the last decade indeed were correct. Mitchell et al. then ran two types of climate models: one ("A") in which only the greenhouse effect was changed (similar to all transient models that based the 1992 Framework Convention), and another ("B") in which a compensating effect of anthropogenerated aerosols was included.

Even though model "A" produced a warming of 2.5°C for doubled carbon dioxide, a relatively low figure, Mitchell et al. stated that it was "significantly different from the observed climate of the last quarter century"-in other words, it was predicting too much warming. They did find that model "B", which appears to calculate only 1.7°C of warming, was consistent with the climate of the last forty to fifty years.

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Figure 2. Comparison of land-based and modelled temperature of the Northern Hemisphere

in the model of Manabe et al., (1991). This type of model was prominently featured in the 1992 Supplementary Report of the U.N. IPCC, which was produced specifically for meeting at which Framework Convention on Climate Change was adopted.

In the most cited ground-based temperature history, that of the U.S. Department of Energy. there is a warming trend of 0.4°C in the same period. Thus model "B" is only projecting an additional warming of 1.3°C (1.7-0.4°) for doubled CO2, which is exactly the value estimated by the "minority" scientists over the last decade.

Nonetheless, I have reason to suspect that this model, too, is not correct. I published two recent papers (Michaels et al, 1994, 1995) that specifically tested the hypothesis that the non sulfate greenhouse effect models would perform best where sulfates would not compromise their forecast (such as the polar regions, particularly Antarctica), and perform worst where the sulfate effects were greatest. If these hypotheses were supported, then it seemed plausible that sulfates were a sufficient explanation for the planet's failure to warm a la the models that based the 1992 Framework Convention update.

The opposite was true. Where there were no sulfates to harm the model, the forecasts were worst. Where the sulfate density was highest (and therefore should have compromised model behavior), the model performed best.

Because model "B", the sulfate + greenhouse model, is so heavily cited in the 1995 IPCC report, it requires close examination in any peer review of that report. From illustrations presented in the draft for reviewers, it became apparent to me that this model might still be reproducing the major error of the circa-1992 models, namely, that it was predicting that too much warming of the high latitudes of the Northern Hemisphere had already taken place. To determine whether or not this is the case required an analysis of the behavior of the high latitude grid cells.

I requested this data for my review of the 1995 IPCC document in an e-mail to the United Kingdom Meteorological Office (UKMO) on May 10, 1995. The next day John Mitchell, one of the lead authors of the IPCC draft, replied that he "felt it inappropriate to send [me] gridpoint data at this time." I replied, on the same day, "I do not understand your statement that it is inappropriate...Science is a cooperative effort in which information should be freely shared... It is, in my mind, not proper to withhold scientific information to a colleague who has been asked by the IPCC itself to review its own work, when that information is critical to the review". The data were not forthcoming.

I then telephoned Dr. Michael MacCracken, head of the U.S. Global Change Research Program, and also head of U.S. review team of the IPCC, stating that I was being refused data absolutely critical to a proper peer review of this important document. He stated that he would be contacting IPCC, but the important data never appeared.

I specifically requested the data required to review this model in other correspondence, making five separate inquiries to IPCC.

There is no doubt their refusal to supply me the model results seriously compromises the scientific review process of climate models that now form the basis for policy proposals to

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