With the Bush administration and Congress failing to act, many states are devising sweeping climate and energy policies that could be a blueprint for a future national climate policy.

In an interview with Yale Environment 360, the chairman of the Intergovernmental Panel on Climate Change says the next U.S. administration must play a leading role in global climate change policy and cautions that China and the developing world must not follow the same path of industrialization as the United States and western Europe.

New evidence suggests that we have already passed a dangerous threshold for the amount of carbon dioxide in the atmosphere and that the time for taking strong action is slipping away.