It's a pleasure-a deep comfort-to have a president who is smarter than most of the rest of us, a president who will be able to deal with complexity. But I have to tell you that, in one sense, there's never been a president who's taken office with a simpler job. I can knock it down to a single number-a number that will set the boundaries for many of the major decisions you must make in what is clearly a perilous time.
That number is 350, and a year ago no one knew it. Shaken by the rapid melt of Arctic sea ice and spurred by mounds of new paleo-climatic data, our leading climatologist at that time, James Hansen at NASA (now one of your employees!), calculated that 350 parts per million of carbon dioxide in the atmosphere was the absolute maximum "if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on earth is adapted." Which, one assumes, you would.
If so, you have your work cut out for you. Because we're already past that number. Two centuries of burning coal and gas and oil have filled the atmosphere with 387 parts per million of carbon dioxide-that's why the Arctic is melting. It's why we're seeing huge increases in storms, why mosquitoes are spreading across Asia and South America, why Greenland is beginning to disintegrate. Forget, say, terrorism-climate change is the one civilization-shaking challenge we face.
The policy implications are large. Essentially, we must get off fossil fuel very, very soon-Hansen said that if humans are still burning coal by 2030, we'll never get back to 350 because we'll have triggered so many feedback loops. That's the biggest job humans have ever undertaken, probably by an order of magnitude: it means every other decision will need to be made in its light. Economy cratering? The way out must be through a radical attempt to create green jobs. Not necessarily because it's the best way to save the economy (though it may well be), but because any other tactic will use up time we can't squander. Foreign policy? Jobs one, two, and three must all be reaching an international agreement that cajoles and bribes China and India into slowing their consumption of coal. Budget policy? If you can't figure out a way to make the U.S. military a climate-fighting force, there's probably not going to be enough cash to get the job done.
There's no question that this new number complicates your life. It sets profound boundaries-boundaries that truly won't yield to rhetoric. (Rhetoric is good stuff-it can change human hearts and minds, so by all means keep it up. It's made it a happy year for me. But it can't change the laws of physics). On the other hand, this number simplifies your job as well. Taken seriously, it immediately closes off a number of paths down which you might otherwise wander.
But it will also require an almost incredible level of nobility. The die will finally be cast during your presidency: the head of the Intergovernmental Panel on Climate Change, Rajendra Pachauri, said recently that if we haven't begun to make fundamental change by 2012, it will be too late to reverse trends (2012-there's a number!). But the worst effects won't be felt until much later, in someone else's reign. It's a moral test of incredible dimension-will you take political pain without much hope of reaping the political reward? It's almost too much to ask, but only almost.
Bill McKibben is cofounder of 350.org, an international grassroots campaign organizing people everywhere to spread the 350 number. He is also a scholar in residence at Middlebury College, and author of Deep Economy.
