Posted on Wed, Aug. 29, 2007

Melting polar ice caps, soaring summer heat and rising sea levels make global warming pretty scary, but some economists see it coolly as just another problem to tackle.

Michael Greenstone, a professor of environmental economics at the Massachusetts Institute of Technology in Cambridge, takes the clinical approach to global warming.

"We're about to undertake very costly policies to mitigate climate change," Greenstone said. "If we want to know how much to spend, we have to know what the damages from doing nothing would be."

Greenstone and colleague Olivier Deschenes, of the University of California in Santa Barbara, recently released a 60-page paper that examines health-related costs related to global warming.

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HOW THEY DID IT

Greenstone and Deschenes realized early that the predicted rise in temperatures due to increased greenhouse gas emissions are within the range of temperature increases seen today.

"Our starting point was that maybe we can look at something from the past to predict the future," Greenstone said.

They collected data from every U.S. weather station over the past 35 years and obtained a database of every single death in the United States over the past 35 years. The death certificate database told them exactly where a person died, cause of death, age and gender.

"What we tried to do is look at places that had abnormally hot days to see if the death rate increased," he said.

Based on their findings, they estimated that climate change would lead to an overall increase of .5 to 1.7 percent in the mortality rate by the end of the 21st century. That number is statistically insignificant, but lead to their economic finding.

The bottom line for the researchers was that the U.S. may not see a very large increase in mortality, but what the country would likely see is many people changing their behaviors.

"The first change in their behavior will be lots of extra energy consumption, or lots of extra air conditioning to be precise," Greenstone said.

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CRANKING UP THE A/C

"When it gets really hot, it's not like you'll just sit around and die," Greenstone said. "You'll make changes in your life that will allow you to carry on."

The economists combined their death data with energy consumption data at the state level for the past 35 years.

"We found a pretty large increase in energy consumption," he said.

They estimate that energy consumption by the end of the century will increase by 15 to 30 percent due to global warming, which is roughly equivalent to $15 billion to $35 billion in 2006 dollars.

The estimated increase in energy consumption will create a feedback loop, since most energy production involves the release of greenhouse gases, Greenstone said. Greenstone and Deschenes believe that current climate models don't account for this feedback loop that would lead to yet higher temperatures.

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WHAT'S NEXT

Greenstone and Deschenes plan to next look at the health impacts from global warming in India where temperatures are already higher than in the United States and people are poorer.

"There could be a lot more death and a lot less increase in energy consumption in response to higher temperatures," he said. "But we don't know, we're going to find out."

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Paul Chavez is an asap reporter based in Los Angeles.