Until recently, its vast forests vacuumed up carbon dioxide. Now that process has been thrown in reverse.
Readers write about a cap-and-trade policy for CO2 emissions, why the West shouldn't lecture China about greenhouse-gases, the need for Afghanistan's neighbors to help contain the volatile country, and mandatory service in the US.
Economic retreat could hamper green investment – but it could also spur a drive to move economies away from fossil-fuel dependencies.
Readers write about extracting oil from shale and tar sands, the challenges Obama will face in Afghanistan, and how Hamas impedes the possibility of peace with Israel.
Experts fear the credit crunch will discourage governments worldwide from turning to taxpayers for assistance in climate-change efforts.