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Global Warming Denialists Misrepresenting Science

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The Tampa Tribune

Published: June 29, 2008

Lorne DeWitt's latest global warming letter is a laundry list of denialist talking points, complete with the ritual denunciation of Al Gore. DeWitt has escalated the rhetoric. In his previous letter, the bulk of the scientific community were "environ-whackos." Now, they're "... sick, demented, pathological liars."

But, rather than engage in mutual hatemongering, let me just answer his claims:

First: CO2 levels have fluctuated over the millennia, true. But ice samples dating back 600,000 years show a variation of 175-280 ppm of CO2. The current level is 385 ppm. That is far higher than the variation over several ice age cycles.

The ice age cycles themselves appear to be related to wobbles in Earth's orbit which vary its distance from the sun. These Milankovich cycles create alternating freezing and warming of the planet.

The planet was never caught in a Little Ice Age, as DeWitt claims. The Little Ice Age is the name given to a period of unusually cold weather in the North Atlantic region. Usually it is dated from 1400 to about 1800 AD; although some say it started in 1300. Nobody knows whether the cold weather was continuous or whether a few extra cold winters got all the "press." There was a 50 year period of observed low sunspot activity from about 1645-1715. This is called the Maunder Minimum and is often associated with the Little Ice Age. As astronomy was primitive in those days, there are serious questions as to whether the Maunder Minimum existed, how long it lasted and whether it had anything to do with the Little Ice Age.

At any rate, a 2006 study by the National Center for Atmospheric Research established that the difference in solar luminosity between peak sunspot years (maxima) and years of low sunspot activity (minima) is only 0.07 percent. (That's seven one hundredths of 1 percent), leading the chief researcher on the project to note: "Our results indicate that, over the past century, climate change due to human influence must far outweigh changes in the sun's brightness."

As to DeWitt's comment that we've been getting more sunlight since the 1980s. True, but it is well established that the "global dimming" prior to the mid 1980s was due to particulate pollution (aka sulfate aerosols) which blocked sunlight but have been steadily reduced by environmental regulations in the developed world.

DeWitt's allegation that the sun is "10 percent hotter" has no basis in fact and borders on the ridiculous.

His comment about global warming on Mars was apparently inspired by widespread media misreporting of a 2005 study of retreating glaciers in the South Polar region of the planet. The study itself made clear that the shrinking ice cap was due to the fact that it was summer. Only the southern hemisphere of Mars was affected.

As to his "30,000 scientists" petition. I have no idea why scientists would sign a petition that makes factual claims about a matter outside their fields of expertise, particularly when it contradicts the established science. I doubt that very many actually did so. Normally, scientists debate by doing research and publishing articles in peer reviewed journals. From time to time, the global warming denial industry conjures up a petition. Reporters actually contacted the signers of a recent petition. It turned out that many of the signers were dead. Others denied having signed. Petitions of scientists are almost always phony.

What DeWitt has done is pass on a bunch of denialist claims that are factually wrong. If he is really interested in learning what's going on, he should bone up on basic science.

Also, in his recent letter, John S.V. Weiss alleges that global warming peaked in 1998. Unfortunately, Weiss has fallen for a misrepresentation that is being circulated by the global warming denier network.

Per the Goddard Institute for Space Studies (www.giss. nasa.gov), the hottest year on record was 2005. The year 2007 is tied with 1998 for second hottest year on record. In fact, eight of the hottest years ever have occurred since 1998.

Far from peaking, the planet's temperature is climbing relentlessly upward.

Dallas Dunlap

Brooksville

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