Some say that today's climate change is merely part of a natural cycle.
In a small college town like Corvallis, Ore., it's not unusual that George Taylor would ride a bike to his job on the Oregon State University campus. He commutes this way for the exercise, he says, but also because it's good for the planet.
Mr. Taylor manages the Oregon Climate Service, and much of his work has to do with global warming. "I'm certainly in favor of doing prudent things to reduce the human impact," he says.
But unlike most climate scientists, he does not believe that anthropogenic (human-caused) greenhouse gases – mainly from coal-fired power plants and motor vehicles spewing carbon dioxide – are the main culprits. In fact, he says, "It's my belief that in the last 100 years or so natural variations have played a bigger role."
Among the forces of nature he cites are changes in solar radiation, "very significant influences" of the tropical Pacific (El Niño and La Niña events in decades-long cycles), as well as changes in Earth's tilt and orbit over cycles lasting thousands of years.
Above all, says Mr. Taylor, who is past president of the American Association of State Climatologists, "The climate system is very, very complex, and the more we learn, the more we see that we really don't understand it."
Taylor may be in the minority among climate experts, but he is not alone.
Other planets in our solar system have expanding and contracting ice caps, too, other skeptics point out, and those worlds have no people as far as we know – certainly no gas-guzzling muscle cars and trucks. Antarctica and Greenland at times have been warm and green before humankind invented machines, indicating to these skeptics that this is just a natural cycle.
In Phoenix, where it's been very hot indeed this summer, Warren Meyer has written "A Skeptical Layman's Guide to Anthropogenic Global Warming." He is not a professionally trained climate scientist, but he studied physics and engineering at Princeton University, then earned an MBA at Harvard University before entering the business world.
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