Europe has the largest market for carbon permits in the world. The idea is, the more a company has to pay for permits to pollute, the greater incentive it has to reduce pollution. But the economic slowdown has greatly reduced the cost of permits.

It's official: Companies must now purchase permits to emit excess levels of carbon dioxide and other greenhouse gases in the state of California.

Global warming didn't get even a mention in the three presidential debates, but a new study says the U.S. is on track to meet its pledge to reduce emissions by one-sixth. A major reason: the power of federal regulation.

Shipping across the ice-free Arctic appears closer than ever. The new route will save fuel, but bring emissions and soot directly to the Arctic -- possibly accelerating the ice melt.