Witness the unveiling of Countdown, a major global campaign to cut greenhouse gas emissions. TED has partnered with scientists, policy makers, organizations, activists and more to create an initiative that everyone in the world can be part of. Check out http://countdown.ted.com to learn how you can get involved — and help turn the tide on climate. [Note: there are two unusual features of this TED Talk. One, it's much longer than our normal, extending a full hour. Two, it's made up of contributions from more than a dozen people, including UN Secretary-General Antonio Guterres, Al Gore, Katharine Hayhoe, Jimmy Kimmel and Yuval Noah Harari, among others. We're putting it out there because the topic deserves this kind of prominence.]

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How do you talk to someone who doesn't believe in climate change? Not by rehashing the same data and facts we've been discussing for years, says climate scientist Katharine Hayhoe. In this inspiring, pragmatic talk, Hayhoe shows how the key to having a real discussion is to connect over shared values like family, community and religion -- and to prompt people to realize that they already care about a changing climate. "We can't give in to despair," she says. "We have to go out and look for the hope we need to inspire us to act -- and that hope begins with a conversation, today."

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The TED Talks channel features the best talks and performances from the TED Conference, where the world's leading thinkers and doers give the talk of their lives in 18 minutes (or less). Look for talks on Technology, Entertainment and Design -- plus science, business, global issues, the arts and more.

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