Chan's Personal Blog

Forget planting trees to negate your SUV's contribution to global warming -- according to Stanford University atmospheric scientist Ken Caldeira, forests in the wrong location can actually make the Earth hotter.

Plants absorb large amounts of carbon dioxide during photosynthesis, so scientists and policy makers have long assumed new forest growth helps combat global warming. At an American Geophysical Union conference in San Francisco earlier this month, however, Caldeira rolled out a provocative new finding: Trees may be good at capturing carbon dioxide from the atmosphere, but their dark leaves are also very efficient at soaking up sunlight, which is later released as heat. At certain latitudes, the net effect of these two processes is warming, rather than cooling.

"Forests do store carbon, and as a result, the planet initially cools a little -- maybe tenths of degrees," Caldeira said. "But over the long term, trees' heat absorption warms things up more." [...]

If future studies confirm Caldeira's findings, his work could have a substantial impact on environmental policy. Currently, programs like Carbonfund and the Chicago Climate Exchange support the planting of temperate forests in various regions of the United States in order to reduce global warming.

In the United Kingdom, for-profit Climate Care offers customers the chance to "cancel out" the carbon-dioxide emissions they produce by donating to a fund that supports reforestation efforts. Its Stratus package, which costs about $130, is billed as making one person "completely climate-neutral for the whole year."

Caldeira's research suggests efforts like these are off base. "Organizations should not be giving these kinds of credits," he said. "Planting forests in mid-latitudes should not be considered equivalent to using renewable resources."