The first commitment period of the Kyoto Protocol covers the five years from 2008 to 2012. Now is the time to start discussing the international framework for the second commitment period, which begins in 2013.

In considering the international framework for the post-Kyoto Protocol era, the crucial question is whether the United States will return to the agreement.

The U.S. accounts for 25 percent of the world's carbon dioxide (CO2 emissions, and without its participation, any agreement for controlling global warming will be ineffective.