I've been dismayed by claims of "good" science and "bad" science that are frequently made these days - where "good" means results that the claimants agree with and "bad" means results that they don't like. So it's refreshing to see the scientific process working as it should in a report that appeared in Science magazine this month. The problem is that temperature data on the earth's surface show unequivocal evidence of global warming that agrees with theoretical models, but satellite records of temperatures in the lower atmosphere over the last 35 years apparently did not. There is lots of other evidence besides surface temperatures to support a conclusion that our globe is warming, but many skeptics based their contrary conclusions on the disagreement between these two sets of results. Real scientists were bothered by the discrepancy, regardless of conclusions they may have reached. As in any scientific work, both sets of data are imperfect. We don't have temperature measurements over every square mile of the earth, for example, and perhaps the data are skewed by too many recordings in warm urban areas. The satellite data are even more questionable since the recordings are less direct. The Bush administration's Climate Change Science Policy Office asked for a report to clarify the issue (one of 21 such studies it requested). The National Climatic Data Center organized the review by scientists including both skeptics and believers, and, to much amazement, they were able to resolve the discrepancies between the two data sets. A unanimous report was issued to the effect that when uncertainties in the data are reduced, the two data sets give the same results over most of the earth. Science magazine announced, "no doubt about it, the world is warming" by about 0.15 degree Celsius (0.27 degree Fahrenheit) per decade, with an uncertainty of about 0.05 degree C (0.09 degree F). Interestingly, the data sets still do not agree in the tropics, and further study will be required to reconcile those differences. Nevertheless, the results of the report were powerful enough to change the position of many skeptics. Gregg Easterbrook, an outspoken skeptic, published an op-ed piece in the New York Times this week acknowledging the significance of new results and his change of mind. I'll admit to a bit of smugness - the satellite measurements are much more complex to interpret than the surface data, so I blame the discrepancy on the satellite data, which showed little or no atmospheric warming. As it turns out, I'm right. But more importantly, the scientific process worked the way it is supposed to. It was possible for objective scientists to look at all the data and reach a common conclusion. Science is a process, not the results of the process. Good science is an objective process, not results that you agree with. Bad science is a subjective process, not results you disagree with. What the new consensus on global warming means for U.S. energy policy remains to be seen. Folks in the White House have yet to admit that they are no longer skeptics. According to the administration's Council on Environmental Quality, Bush continues to believe that greenhouse emissions can be brought down by better use of energy, whatever that means. There is much left to learn about global warming, but now there is one fewer puzzle to solve. The biggest question is what, if anything, we should try to do about it. As I reported a few weeks ago, California has announced its intention to rely on energy sources that produce less carbon dioxide, a strategy I don't see the current president endorsing. The argument about whether or not the globe is warming is effectively over, thanks to good scientific work. We humans are indeed increasing the amount of heat trapped by the atmosphere, primarily because of the amount of fossil fuels we burn. Now the debate can focus on what to do about it.
