After failing to pass a climate bill through a Democratic-controlled Congress, he proposed rules to control heat-trapping pollution from future power plants.
Due to the subtropical summer heat and the pollution that blows down from the factories on the Chinese mainland, Hong Kong is a punishing place to run.
Any policy to reduce heat-trapping pollution will inevitably target the main sources of Americans' energy: the coal burned by power plants for electricity and the oil that is refined to run automobiles.
Such a change in temperature -- which many scientists believe is being caused by pollution trapping heat in the atmosphere -- would mean widespread droughts and floods and massive economic and natural damage, experts say.