The conclusion that observed climate change is our fault rests on the pattern of warming, too. As it happens, "human and natural factors that affect climate have unique signatures," says climatologist Ben Santer of Lawrence Livermore National Laboratory, part of the U.S. Department of Energy. The clearest signature is differences in the warming of different layers of the atmosphere. According to satellites and weather balloons, the lower atmosphere, or troposphere, has warmed; the upper atmosphere, or stratosphere, has cooled. That's not what a hotter sun would do. "If you increase output from the sun, you increase the amount of energy that arrives at the top of Earth's atmosphere," says Santer. "And you get heating throughout the whole column. Have we observed anything like that? The answer is a very clear no." Greenhouse gases such as carbon dioxide from the burning of coal, oil and natural gas and methane from, among other surprising sources, rice fields (where bacteria thriving in the submerged paddies release this and other gases) act from the bottom up. That is, they warm the troposphere and cool the stratosphere by trapping heat waves wafting off the planet's surface. The warm troposphere and cool stratosphere "is entirely consistent with our best understanding of how temperatures would change with an increase in greenhouse gases," says Santer.
But that raises a question for those who emphasize nature's contributions to global warming and other aspects of climate change. Let's suppose that those are nudging the climate toward worse storms and more droughts and more heat waves, just as greenhouse gases are. In that case, you'd think the world would want to control the causes of global warming that it can. At last check, no one had figured out how to turn down the sun.
This article has a good. understandable explanation of why climate scientists overwhelmingly believe the global waming we are experiencing is from man-made, rather than natural sources.
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