In 2007 the Intergovernmental Panel on Climate Change-representing a global consensus of hundreds of scientists-concluded that "warming of the climate system is unequivocal," citing observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.

And they noted that human activity is "very likely" the cause. Whatever your views on climate change, it's important to understand how the current scientific consensus on global warming evolved out of basic physical principles and a broad range of observations.

This lucid series of twelve lectures is designed to do exactly that-reviewing the most up-to-date research and explaining the concepts, tools, data, and analysis that have led an overwhelming number of climate scientists to conclude that Earth is indeed warming and that we humans are in great part responsible.

In clear and accessible lectures designed for nonscientists, you'll learn about the "fingerprints" of global climate change-ranging from borehole temperatures to melting glaciers to the altered behavior of plant and animal species and other indicators-that convince scientists that our Earth has been warming at an unprecedented rate in recent decades. The lectures address only scientific issues and make no policy recommendations. Instead, they have been designed to serve as your personal scientific briefing to equip you to engage knowledgeably in one of the most important environmental issues of our time.