The evidence continues to mount: melting ice caps, rising temperatures, increasingly frequent natural disasters. As the devastating effects of global warming come into sharper focus, societies must work to both mitigate greenhouse gas emissions and adapt to ongoing and inevitable climate change. The actions taken in the coming century will be critically important in determining whether or not we can salvage our environment. We cannot shrink from the overwhelming magnitude of climate change or the radical solutions it demands. The Worldwatch Institute’s State of the World 2009 investigates a wide range of potential paths to change, including new technology, policy changes, consumption, and finance, with the ultimate goal of mobilizing humanity around climate change and revealing global warming as one of the truly great challenges of our time.