One of Bob Parson's (Godaddy.com) 16 rules to live by talks about not only accepting the worst thing that can happen, but actually quantifying it. Very seldom will the worst thing that can happen be as bad as a cloud of undefined consequences. Check out the government's latest attempt at quantifying climate change over the next 25-50 years:
While it looks scary....I usually imagine these changes happening much more rapidly. It makes sense that they would take a long time to fully unleash their consequences. There's no denying we need more action as soon as people can take it, but it's just a better life to imagine we do have hope and that we're not irreversibly destroying the planet right now. I sometimes think the people who truly believe we're completely doomed are as much a part of the problem as people in denial about the whole thing.