In a 2007 report, a panel of United Nations scientists said evidence that man was causing global warming is "unequivocal." Earlier this month, 650 scientists from around the globe criticized the finding in a U.S. Senate minority report.

But while some groups, scientists, politicians and Web sites, like www.globalwarminghoax.com, rebut any link between man and rising global temperatures, local scientists say there is no longer any debate on the matter.

"There is almost no debate anymore over the fact that the Earth is getting warmer due to the emission of greenhouse gases from consumption," said Christopher Lant, a professor at Southern Illinois University Carbondale who specializes in water resources. "That is as close to settled as you can get. The debate now is over how severe are the impacts from a human standpoint and what should be done about it."

Justin Schoof, an atmospheric scientist at SIUC who studies global warming, agreed.

"The question amongst scientific groups if global warming is human induced has pretty much been put to rest," Schoof said. "There are a few, maybe four or five scientists, that are very well-respected that still have doubts about whether humans are responsible for climate change."

Schoof said most widely credited models show temperatures will increase between 5 and 9 degrees in the next 100 years.

"But if we change our ways and embrace new energy technologies now, we could certainly be on the low end of the range," he said. "It's reversible, but it's going to take a long time."

Much of the recent popular debate about global warming has included warnings that a tipping point is at hand, or has already been crossed. Worst-case scenarios say increased carbon emissions have set off a domino effect that begins with warmer temperatures and moves on to disasters, among them extreme weather events, global catastrophes in agriculture and disease.

But Schoof said it might not be so simple.

"There are many, many tipping points in the climate system," he said. "Different parts of the climate system that could reach tipping points at different times. Perhaps the most important point is that it's almost a guarantee that there are tipping points that we don't know of."

Steven Kraft, an agricultural economist at SIUC, said that while the planet's response to higher temperatures might not be known, one can look at what the remnants of Hurricane Ike did when they crossed Southern Illinois in September.

High winds from the storm flattened local corn crops, he said, making them far more difficult and expensive to harvest.

"If you remember, we don't normally have winds like that coming through here," Kraft said. "The cost to farmers to harvest shot up very quickly just as a consequence of that one storm. That is an indication of how something as small as the increase in the severity or frequency of storms can have a real impact on agriculture."

blackwell.thomas@thesouthern.com

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