The vast majority of scientists agree that human activity has significantly increased greenhouse gases in the atmosphere--most dramatically since the 1970s. Yet global warming skeptics and ill-informed elected officials continue to dismiss this broad scientific consensus. In this new edition of his authoritative book, MIT atmospheric scientist Kerry Emanuel -- a political conservative -- outlines the basic science of global warming and how the current consensus has emerged. He also covers two major developments that have occurred since the first edition: the most recent round of updated projections from the Intergovernmental Panel on Climate Change climate simulations, and the so-called "climategate" incident that heralded the subsequent collapse of popular and political support in the United States for dealing with climate change.