It is New Year’s Day, 2101. Somehow, humanity survived the worst of global warming—the higher temperatures and sea levels and the more intense droughts and storms—and succeeded in stabilizing Earth’s climate.

What did humanity do in the twenty-first century, and especially in 2009 and the years immediately following, to snatch a threatened world from the jaws of climate change catastrophe? State of the World 2009 examines solutions that may help us avoid climate catastrophe and build a sustainable society.