We really don't know what's going to happen in the next 20 years. Most predictions made by experts about the future are wrong. I very much doubt we're heading for the Apocalypse that some environmentalists claim. As someone above said throughout history climates have changed dramatically. Thousands of years ago Egypt was a green land, and England had Meditterranean weather.
I can't see much being done about global warming while people still like to use cars and fly to foreign countries for their holidays. And I don't see that many people willing to give them up or any government, who want to stay in power, forcing them to.