AGW: How We Know It's Bunk

AGW: (Anthropogenic global warming) How We Know It's Bunk

As the Obama administration takes shape, one important issue that will come to the fore is climate change. On this issue, like so many others, the Bush administration was rather schizoid: Bush himself acknowledged the "reality" of global warming, thereby ceding the issue on principle, but his sounder instincts caused him and his administration to drag their feet on doing anything that would be ruinous to the economy. Obama so far has displayed no such ambivalence. At present, there is no reason to doubt that his administration will try to implement severe measures in hopes of changing the world's weather.

So it is vitally important to revisit the argument over whether climate change, a constant throughout the earth's history, is driven principally by human activities and therefore lies largely within human control. The go-to source on this question is the Science and Environmental Policy Project. This is an excellent summary (Part 1, more to follow) from SEPP on the central issue in the global warming controversy: does the observed "footprint" of warming in recent decades correspond to the temperature patterns that are predicted by the computer models that ostensibly support the anthropogenic global warming theory?

The crucial question is: Is warming (predominantly) due to natural or human causes? How can one tell? The issue is of obvious importance since natural causes cannot be influenced in any way by policies that limit greenhouse (GH) gas emissions, such as CO2. Resolving the question is a difficult scientific task. Natural causes are plausible; the climate has been warming and cooling for billions of years on many different time scales [See, e.g., Singer and Avery 2007]. On the other hand, GH warming is also plausible, since the concentration of GH gases has been increasing due to human activities.

The method agreed to by everyone is the "fingerprint" method, which compares the pattern of temperature trends calculated from GH models with the pattern observed in the atmosphere. The first application of this method may have been by Santer et al in IPCC-SAR [1996]. However, Santer misapplied the method in order to force the conclusion that warming was due to human causes, namely GH gases.

In one attempt, he compared the geographic pattern of surface temperature trends, derived from GH models, with the observed pattern. He calculated a "pattern correlation coefficient" and claimed that it was increasing with time "as the human signal emerged from the background noise of climate variability" [IPCC-SAR, 1996, chapter 8]. However, when the graph there is compared to the one in his original publication [Santer et al 1995], one discovered that he had removed all of the trend lines, including zero and negative trends, except the one that suggested an increasing correlation in the last 50 years [Singer 1997]. When questioned about this by e-mail, he replied that it was done for "pedagogic reasons"**

Santer's second attempt, also in chapter 8 of IPCC-SAR, was to compare the modeled and observed latitude and altitude patterns of temperature trends. It was soon discovered, however, that his claimed "agreement" was due to a selective use of data; he had chosen a time interval (1963-1987) during which the tropospheric trend was increasing, while the overall trend during the period (1957-1995) was not [Michaels and Knappenberger 1996].

By then it had become quite apparent that there was a disparity between the observed trends in the troposphere and the surface [NRC 2000; Singer 2001]. Douglass, Pearson and Singer carried out a full-scale comparison of available model results and temperature observations from balloons, satellites, and reanalysis [2004]. They concluded that the observations did not confirm the expected increase (from GH models) in temperature trends with altitude in the tropics; but they did not delve into the implication of this disparity. As a result, their result was largely ignored.

Next, a full-scale investigation of this problem was carried out as part of the federally financed Climate Change Science Program. CCSP-SAP-1.1 [2006], the first and most crucial of the 21 reports of the CCSP, titled "Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences," confirmed the result of Douglass et al [2004].

To be sure, the abstract of CCSP 1.1 claims that the discrepancies between surface warming and tropospheric warming trends have been removed. This statement distorts the sense of the CCSP report and has been widely misunderstood as having confirmed the validity of GH models. CCSP-1.1 admits, however, (p.3) that in the tropics "the majority of observational data sets show more warming at the surface than in the troposphere....[but] almost all model simulations show more warming in the troposphere than at the surface." In other words, there exists indeed a discrepancy, which has not been removed. This Executive Summary was authored by Wigley, with the participation of the chapter lead authors, including Santer.

Following the publication of CCSP 1.1, and using best available models and data, Douglass, Christy, Pearson, and Singer [2007] extended their comparison between model results and observations in the tropical zone and concluded again that the observations did not confirm the GH model results. This paper was also ignored until a group of independent scientists, the Nongovernmental International Panel on Climate Change (NIPCC) published its summary report in 2008. Drawing mainly on the data from CCSP-1.1 and Douglass et al [2007], NIPCC [Singer et al 2008] showed conclusively the disparity between GH models and observations.

The NIPCC then drew the obvious logical conclusion: Since GH models cannot explain the observations, the warming of the past 30 years must be due predominantly to causes other than GH gases. In other words, the human contribution to the warming trend since 1979 is minor and insignificant - a conclusion contrary to that of IPCC [2007]. Another way of stating the NIPCC result: Climate Sensitivity is considerably less than the values quoted by the IPCC, i.e. 1.5 - 4.5 C, and more in accord with the much lower values deduced by other methods [Schwartz, Monckton, Lindzen, Spencer].

It will be interesting to see whether the Obama administration proves to be open to backtracking on AGW. As noted above, there is no sign of such indecision so far. But poll data indicate that most Americans don't buy the global warming theory, notwithstanding (or maybe because of) unremitting propaganda from the Left. And whatever mandate Obama may or may not have, he certainly does not have a mandate to devastate the economy through ill-considered environmental measures.

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