Here are the facts. Over the course of the 20th century the average global temperature went up about 1.3 degrees Fahrenheit. We now know that this rise was primarily the result of human emission of greenhouse gases into the atmosphere. In 2006 the Intergovernmental Panel for Climate Change (IPCC) estimated that in the 21st century the global temperature could increase another 2.0 to 11.5 degrees. Even at the low end of that projection, the risks of disruptions to terrestrial and ocean ecosystems, extinction of plants and animals, and increased number of extreme weather events are uncomfortably high. If the global temperature increases 6.3 degrees, the risks to all sectors of our planet, from plants and animals to economic stability, would increase dramatically.

This realization will bring 200 countries to the bargaining table in Copenhagen in December 2009, with the primary aim of agreeing on an international plan to decrease greenhouse gas emissions. The fate of our lives and the lives of future generations depend largely on the outcome of the Copenhagen meeting. It would be hard to overestimate how consequential this moment is.

This course was originally presented in Stanford's Continuing Studies program.

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