Why I must voice concerns about climate change - James Hansen

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View full lesson: http://ed.ted.com/lessons/why-i-must-speak-out-about-climate-change-james-hansenTop climate scientist James Hansen tells the story of his involvement in the science of and debate over global climate change. In doing so he outlines the overwhelming evidence that change is happening and why that makes him deeply worried about the future. Talk by James Hansen. Learn more about your ad choices. Visit megaphone.fm/adchoices