December 15, 2006

Scientists: Planting Trees No Cure for Global Warming

As Green Wombat reported Thursday, California utility Pacific Gas & Electric will invest in forestry projects to neutralize greenhouse gas emissions from its customers' energy use. Today, scientists presenting research at a San Francisco conference said, in effect, don't bother. At least not in North America and Europe. The reason: computer modeling shows that while trees indeed do remove carbon dioxide from the atmosphere, in the planet's mid-latitudes their dark leaves also absorb heat and thus have a marginal benefit in reducing global warming, according to Govindasamy Bala, a climate scientist at Lawrence Livermore National Laboratory in California. If the scientists' findings are confirmed by further research, it could spell trouble for corporate efforts to mitigate companies' contributions to global warming by planting trees rather than taking action to actually reduce their emissions of greenhouse gases. "This suggests that planting forests would not slow down global warming," Bala told fellow scientists attending the big American Geophysical Union confab as he showed slides depicting the results of the study he co-authored. Tree-planting also is being used by so-called carbon offset services that promise to neutralize consumers' personal emissions of carbon dioxide from driving, flying and their consumerist lifestyle. It makes more sense, Bala said, to plant trees in the southern hemisphere as tropical forests also absorb more water vapor, creating clouds that cool the planet. Bala cautioned that his conclusions come from a preliminary investigation based on computer modeling of what would happen if the planet was deforested - temperatures would drop slightly, the scientists found - and not on actual on-the-ground measurements. "Forests have a lot of value in our economy and for ecosystems," Bala emphasized.

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THIS REPORT WAS ISSUED WITH STANFORD.