Ralph Nader once said that it would likely be up to a small group of intelligent and wealthy people to save the planet by stepping in when government fails. And that is just what these five men are doing.

In the last week two big announcements came from two multibillionaires — Bill Gates, who announced his pledge to find and fund clean energy solutions, and Richard Branson, who announced a "war on carbon" through a Green Capital Global Challenge which will fund the greening of 10 cities around the world.

The private sector may lead the way, but can they solve the whole problem? What do you think? Leave comments below.

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