A press release from the federally supported National Center for Atmospheric Research (NCAR) claims a “New Look at Satellite Data Supports Global Warming Trend.” That claim is likely to be trumpeted by supporters of the Kyoto Protocol, who want to restrict drastically the use of energy in the U.S. and abroad.
But the NCAR findings are based on the wishful thinking of well-known global-warming promoters, rather than on sound science.
The NCAR findings were reported by the journal Science on May 1 at http://www.sciencexpress.org, well before the normal publication date and just before hearings by Sen. John McCain (R-Arizona). Coincidence?
The lead author of the NCAR report is Ben Santer of the Lawrence Livermore National Laboratory–who became notorious for surreptitiously altering the text of a crucial chapter in the 1995 Intergovernmental Panel on Climate Change’s Report on Climate Change in order to make it conform to its politically inspired Summary for Policymakers.
The NCAR study is based on an analysis of weather satellite data by Frank Wentz and colleagues at Remote Sensing Systems (RSS); they proclaim a warming trend of about 0.1° Centigrade per decade between 1979 and 1999. These results are at odds with previous analyses of the same satellite data by John Christy and Roy Spencer of the University of Alabama at Huntsville (UAH), who found virtually no warming over the 20-year period.
Over the past 25 years, a series of instruments aboard 12 U.S. satellites has provided a unique temperature record extending as high as the lower stratosphere. Each sensor intercepts microwaves emitted by various parts of the atmosphere, with emissions increasing if temperatures rise. These data are used to infer the temperature of key atmospheric layers, the (lower) troposphere and (higher) stratosphere.
Since the 1990s, the absence of an observed warming signal in the satellite-derived lower-atmospheric temperatures has stood in contrast to a distinct warming trend in temperature at Earth’s surface. A 2000 report from the National Research Council concluded both trends might be correct–in other words, the global atmosphere might be warming more quickly near the ground than higher up. By contrast, all theoretical climate models predict a higher rate of warming for the troposphere than for the surface.
Clearly, the RSS results would be a closer match with surface warming, as well as with computer-model simulations, and are therefore preferred by the NCAR group. But are the RSS results correct? I don’t think so:
- Wentz presented the RSS analysis of the satellite data on December 4, 2002, in Washington DC at a panel organized by the federal Climate Change Science Program. Christy, Santer, and I were members of this panel and heard his presentation, but there was no time for discussion of his startling results. However, Wentz was kind enough to give me a copy of his full paper so I could study it.
It is a careful piece of work that must be taken seriously; but of course, that does not make it correct. I mailed him a number of comments, to which his co-author Carl Mears responded. I then suggested they perform some crucial tests on the internal consistency of their results, but there has been no reply so far. I did receive comments from Christy that discussed the weak points in the RSS work.
- Independent atmosphere temperature data from radiosonde instruments carried aloft in weather balloons do not support RSS but agree with the UAH result of a negligible warming trend (which will become even smaller as the huge 1998 El Niño warming is gradually washed out). Of course, the balloon data have problems of their own that require correction; but the latest reanalysis has further reduced the trend result. On the other hand, the surface data at weather stations are subject to large corrections as well. A most important one–and difficult to remove completely–is the well-known “urban heat-island” effect, the local heating produced over time by the expansion of housing, traffic, and energy release in the vicinity of the stations.
- Finally, we have a large amount of non-instrumental data. Such proxies include measurements of the widths of tree rings, isotope data from ocean and lake sediments, ice cores and corals, etc. All of these can be calibrated in terms of temperature. I have personally examined many of these published results and have yet to find any that show a recent warming. It is another strong piece of evidence that supports the conclusion that the surface data from weather stations are contaminated by local heating effects and cannot be relied on to support global warming.
But if the RSS analysis is not correct, then the NCAR study is mostly hot air. As science journalist Ron Bailey points out: “Evidently, the strategy being used by Santer et al. is that if their models don’t agree with the data, then change the data.” Our hope is that Congress does not buy into this shell game.
S. Fred Singer is professor emeritus of environmental sciences at the University of Virginia and president of the Science & Environmental Policy Project. http://www.sepp.org His email address is [email protected].