Earth nears tipping point on climate change

A rise of 1 degree Celsius could be enough to trigger 'dangerous' warming, scientists warn.

from the May 30, 2007 edition

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Dangerous climate change has not yet arrived, but the tipping point may not be far off. And it may be reached with a smaller temperature rise than recent studies suggest.

Those are among the conclusions from an international team of climate scientists in a study this month, which they say bolsters the case for an alternative strategy to combat climate change. The main idea: focus intensely on cutting greenhouse-gas emissions other than carbon dioxide in the short term, giving the world a little leeway in dealing with the trickier issue of CO2.

Most climate scientists point to rising carbon-dioxide levels from burning coal, oil, and gas as the main driver behind global warming. But the international team says that fighting ozone, soot, and other pollutants, which also can warm the atmosphere, could allow CO2 levels to rise a little higher without reaching the tipping point.

"This is good news," notes Gavin Schmidt, a member of the research team and a scientist at NASA's Goddard Institute for Space Studies (GISS), in an e-mail. "There is scope for effective action, even though it will fall short of stopping human-caused climate change completely."

Yet this more comprehensive approach to curbing emissions is unlikely to remain an option for too long, according to James Hansen, a climate scientist also at GISS and lead author of the study. If global CO2 emissions continue on their current "business as usual" path for another 10 years, he notes, "it becomes impractical to achieve the alternative scenario." The business-as-usual approach allows too many fossil-fuel intensive power plants and factories to be built – investments designed to last for decades, he adds.

While the 10-year window doesn't represent a "drop dead" date, the researchers say, it should be seen as a transition period during which CEOs take emissions-reduction needs into account as they lay out spending plans for new factories and offices, power plants, and lines of cars and trucks.

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