James Schlesinger has a great piece on global warming in today's WSJ:
- Almost unnoticed, the theology of global warming has in recent weeks suffered a number of setbacks. In referring to the theology of global warming, one is not focusing on evidence of the earth's warming in recent decades, particularly in the Arctic, but rather on the widespread insistence that such warming is primarily a consequence of man's activities -- and that, if only we collectively had the will, we could alter our behavior and stop the warming of the planet.
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The issue of climate change urgently needs to be brought down from the level of theology to what we actually know. It is, of course, quite likely that the greenhouse effect has to some extent contributed to global warming -- but we simply do not know to what extent. The insistence that global warming is primarily the consequence of human activity leaves scant room for variation in solar intensity or cyclical phenomena generally.
Over the ages, climate has varied. Generally speaking, the Northern Hemisphere has been warming since the end of the Little Ice Age in the 17th century. Most of the global warming observed in the 20th century occurred between 1900 and 1940, when the release of greenhouse gasses was far less than later in the century. Between 1940 and 1975, temperatures fell -- and scientists feared a lengthy period of global cooling. The reported rise in temperatures in recent decades has come rather suddenly -- probably too suddenly given the relatively slow rise of greenhouse gases in the atmosphere.
We must always bear in mind that the earth's atmosphere remains a highly complex thermodynamic machine. Given its complexities, we need to be modest in asserting what we know. Knowledge is more than speculation.