Syndicated columnist Cal Thomas recently noted that Arctic Ocean ice cover in late summer last year was 409,000 square miles larger than two years earlier. He used the data to express skepticism about so-called global warming.

An astute reader of the Lansing State Journal took him to task for offering too limited a perspective. The reader investigated statistics from a group called the National Snow and Ice Data Center (NSIDC) based at the University of Colorado in Boulder.

It turns out that the 2009 ice extent was still relatively small, nearly 24 percent below the 1979-2000 average. The "lowest on record" was in 2007, and increases since then merely made 2008 the second lowest and 2009 the third lowest. From 1980 to 2007 the ice coverage shrank by roughly one-third. An NSIDC official cautioned in a press release against assumptions of a return to "conditions seen back in the 1970s."

The headline chosen for the rebuttal was "Thomas was selective on arctic ice report."

Of course, the broader data are also "selective." The reference point is 1979 and 1980. But the 1970s included a series of brutally cold winters. So was the ice extent in '79 and '80 abnormally large? What were the figures in the 1960s and 1950s? What was the ice coverage in the 1930s, a decade of searingly hot summers? How did the 1930s compare with the 1920s? And with the warm 1910s?

As far as that goes, how do the present conditions stack up against the warming of a millennium ago when Greenland was more habitable for human settlement than today?

The answer, of course, is that nobody knows. A precise record began with satellite images about 30 years ago. Everything before that is in a sense prehistoric. So talk about "the lowest on record" refers to only a three-decade span, a mere blink in time. Generalizations from such limited data are immediately suspect.

Manipulation of statistics through selective use of base points is a treasured tactic in the pseudosciences. Climatologists Patrick J. Michaels and Robert C. Balling Jr., in their 2000 book "The Satanic Gases," offer an example that would be amusing if it were not so chilling.

The United Nations sponsored a conference in Kyoto, Japan, in 1997 to bind certain nations to targeted emissions reductions of so-called greenhouse gases. The groundwork was laid in previous meetings, including one in Geneva, Switzerland, in 1996. Four days before it started, a paper was published in a leading scientific journal alleging a "human fingerprint" on purported warming between 1963 and 1987.

Michaels and Balling immediately saw a red flag. Data were available between 1958 and 1995. So why was the study constricted to the shorter period? A major volcanic eruption occurred in Indonesia in 1963, soon skewing global temperatures downward and providing a nice take-off point for demonstrating later warming. In a simple step, Michaels and Balling added the data prior to 1963 and after 1987. All of a sudden the "warming" line on a published graph flattened. This "confirmation" of human-caused warming crumbled.

Michaels flew to Geneva with a one-page summary exposing the deception. His work was warmly received by attendees opposed to mandated emissions reductions, but was railed against by advocates. One was a Clinton administration official who viewed criticism of the global warming party line as being raised by "naysayers and special interests bent on belittling, attacking and obfuscating climate change science."

Given the complexities of climate, "climate change science" is a product susceptible to overselling. So far it can't even explain the Ice Age. For all the mistiness on its rear-view mirror, it peers even more blurrily into the future through a foggy windshield. A "scientific" guess is still a guess.

But not to the true believers. They degrade the skeptical spirit essential to scientific inquiry into a device for obfuscating, attacking and belittling. Skeptics are branded "special interests." The warning message: Desist from dissent.

The chill that hangs over "climate change science" is the progressive subverting of science into a parasitic propaganda adjunct of ideology.

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Daniel Hager is an adjunct scholar with the Mackinac Center for Public Policy, a research and educational institute headquartered in Midland, Mich. Permission to reprint in whole or in part is hereby granted, provided that the author and the Center are properly cited.