DALLAS – The effects of global warming will be felt for several centuries even if the world’s nations could somehow immediately stabilize the amount of heat-trapping “greenhouse” gases in the atmosphere, two new computer modeling studies suggest.
Were gas levels held constant, worldwide temperatures would still rise about 1 degree Fahrenheit by 2100, while sea level would rise more than 4 inches, according to one of the studies.
The research is the most detailed look yet at how the world is irrevocably committed to climate change.
“The longer you wait, the worse it gets,” said lead researcher Gerald Meehl, a senior scientist at the National Center for Atmospheric Research in Boulder, Colo.
“That may be kind of an obvious thing,” he said, “but with each passing day and week and year, the more greenhouse gases we put into the atmosphere commits us to even more climate change in the future.”
A second study, by climate expert Tom Wigley, used a simpler computer model than Meehl’s, but reached similar conclusions. Both studies appeared in a recent issue of the journal Science.
“No matter what we do, the climate is going to change pretty significantly in the future,” said Wigley, also of the national atmospheric center. His study showed that sea levels could rise 10 inches each century through 2400.
People affect climate by putting extra amounts of greenhouse gases, such as carbon dioxide and methane, into the atmosphere through the burning of fossil fuels and other industrial activities.
Meehl’s study used two sophisticated computer models to simulate both past and future climate. Future studies were based on the assumption that greenhouse gas concentrations would stay at what they were in 2000.
Loaded with data points to simulate all aspects of the atmosphere, oceans and land, the models ran for months on some of the world’s most powerful computers. Both came up with similar results, with slightly more warming in the newer and more complex model.
The predicted 1-degree temperature rise is similar to the global warming observed during the latter half of the 20th century, said Meehl. But the real surprise was that the oceans would continue rising until at least 2500.
“That was the thing that got my attention,” he said. Rising sea levels threaten not only to drown coastal communities but also to cause more damage inland during storms because of higher storm surges.
The study accounted only for how much sea level would rise because of thermal expansion – the fact that water expands when it gets warm – and did not include the extra water that would be added into the oceans by melting glaciers or ice sheets.
“They’re really working at the lower end of the scale, so if these numbers give people pause for thought, then in the real world it’s going to be a heck of a lot worse,” said Tim Barnett of the Scripps Institution of Oceanography.
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AP-NY-03-24-05 0621EST
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