Green philanthropy got a major shot in the arm in September when Virgin CEO Richard Branson announced that he was giving $3 billion-the anticipated profits from Virgin Group's airline and rail businesses-to fund renewable energy research and development by non-profit organizations and for-profit businesses during the next 10 years. It was perhaps the largest amount of cash that any single person had devoted to the renewable energy cause in one fell swoop.

Hello, optimism. Goodbye, doom, gloom and futile handwringing.

Green philanthropy is suddenly hot, as it takes on the climate crisis with big money and fresh tactics.