Weather MattersAugust 20, 2000Published in the Mid-Valley SundayGeorge H. Taylor, State Climatologist |
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Global Warming Theories Questionable
In 1988, during an extremely hot, dry summer, Dr. James Hansen of NASA told a Senate subcommittee, "with 99% confidence...global warming is affecting our planet now." He went on to say "it is time to stop waffling," and that severe emission controls on carbon dioxide and other "greenhouse gases" should be implemented.
Hansen's computer models at the time showed that a doubling of CO2 in the atmosphere would cause tremendous temperature increases -- 10-15 degrees F, which is pretty close to natural variations from ice age to milder periods over the last few million years. In the 1970s, the big climate fears involved "the coming Ice Age," but following Hansen's testimony the real concern became "global warming."
Hansen talked about an "enhanced greenhouse effect." The atmosphere has been likened to a giant greenhouse because of the presence of certain "greenhouse gases" which allow light from the sun to reach the earth but trap infrared radiation (heat), causing the atmosphere to be much warmer than it would be otherwise. Water vapor accounts for a very significant percentage of the greenhouse effect, especially in warmer climates, while CO2, methane, and other trace gases account for the remainder. Without the greenhouse effect, the atmosphere would be about 60 degrees F colder than it is now, and life as we know it would simply not exist. "Global warming" is based on the theory that if we increase the amount of greenhouse gases we raise the earth's temperature.
At the time, I went along with Hansen's theories. I even participated in the "Oregon Global Warming Task Force," which produced a set of recommendations for how Oregon could reduce its emissions of CO2 in order to do its part to combat global warming. This follows the time-honored slogan "think globally, act locally" which I endorse. If everyone cleaned up their own part of the world, the world would be a cleaner place!
But 4 or 5 years ago I began to doubt some of the global warming projections. I was challenged by state climatologists in several other states to "examine the data." I began studying the literature more systematically. And I concluded that the effects of CO2 and other greenhouse gases on global temperatures would be quite a bit less severe than Hansen (and I) had concluded earlier.
I still believe that if we continue to increase the amount of greenhouse gases in the atmosphere that temperatures will increase (all other things being equal). I still believe that there are lots of good reasons to reduce our usage of fossil fuels and other things that emit greenhouse gases (that's why I ride a bicycle as often as possible, even in winter). But I believe that the human contribution to climate change is a great deal smaller than natural variations. I looked at the evidence and I changed my mind.
I've expressed that opinion in public on a number of occasions, and have incurred the ire of many people. I have been called "irresponsible," "an idiot," "dangerous," and other names. I have heard statements like "the vast majority of credible scientists believe that global warming is a significant problem that must be dealt with immediately." In other words, I'm either in a tiny minority or I have no credibility!
Next week: a surprising new development in
James Hansen's opinions
George Taylor is the State Climatologist for Oregon, and is a faculty member at OSU's College of Oceanic and Atmospheric Sciences. Send your weather-related questions to him at:
Oregon Climate Service
316 Strand Ag Hall
Oregon State University
Corvallis OR 97331
Voice: 541-737-5705 Fax: 541-737-5710
e-mail: taylor@oce.orst.edu Web: www.ocs.orst.edu