I'm at the TTI/Vanguard conference and have just had the honor of hearing a presentation by James Lovelock, one of the historical leaders and visionaries of global environmentalism.
His message is pretty straightforward. I'll try to paraphrase it here: We've screwed things up so much that we have to start thinking of big things we can do to counteract the mess we've made. Nothing we can do as humans can operate at a large enough scale and fast enough to stop the processes we've put into place. What we need to do is use the power of the earth itself to correct the problem.
He's proposing a systems approach to the earth, and with radical ideas like large scale heat pumps. He believes is that we're already making dramatic changes to the earth, so the risk of other radical changes is negligible compared to what we're already doing.