Our climate is now changing at a rapid rate, and even greater climate change is very likely in the 21st century. Temperatures are projected to rise more rapidly in the next one hundred years than in the last 10, 000 years. This Assessment has involved thousands of Americans in an ongoing national dialogue about climate change and its impacts. The report identifies key climatic vulnerabilities of particular regions and sectors in the context of other changes in the nation's environment, resources, and economy. It also explores ways Americans can adapt to an uncertain and continuously changing climate.