By Bill McKibben


Let’s say you’re interested in the outdoors. Maybe you like to wander around in it: hiking, skiing, swimming, surfing, biking. Maybe you like to sell people hiking boots, skis, bathing suits, surfboards or handlebar extensions. Maybe you like to do both.


In that case, what you need to understand, at the very core of your being, is that the world is changing, and changing fast. The planet on which hiking and skiing and surfing makes sense is suddenly turning into a different planet. Not in our children’s time, not in our grandchildren’s time. In our time, right now. As we watch.


There’s a number-a new number-that makes this point most powerfully. It may now be the most important number on Earth: 350. As in parts per million of carbon dioxide in the atmosphere.


A few months ago, NASA’s chief climatologist, James Hansen, submitted a paper to Science magazine with several coauthors. The abstract attached to it argued-and I have never read stronger language in a scientific paper-that “If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm.”


Hansen cites six irreversible tipping points, massive sea level rise and huge changes in rainfall patterns among them, that we’ll pass if we don’t get back down to 350 soon. The first of them, judging by last summer’s insane melt of Arctic ice, may already be behind us.


It’s a tough diagnosis. It’s like the doctor telling you that your cholesterol is way too high and if you don’t bring it down right away, you’re going to have a stroke. So you take the pill, you swear off the cheese, and if you’re lucky, you get back into the safety zone before the coronary. It’s like watching the tachometer edge into the red zone and knowing that you need to take your foot off the gas before you hear that clunk up front.


In this case, though, it’s worse than that because we’re not taking the pill and we are stomping on the gas-hard. Instead of slowing down, we’re pouring on the coal, quite literally. Two weeks ago came the news that atmospheric carbon dioxide had jumped 2.4 parts per million last year. Two decades ago, it was going up barely half that fast.


So, let’s say you want to do something about that. What could you do?


Well, you could change your light bulbs, you could convert your delivery van to use veggie oil, and you could buy carbon offsets for your snowmaking equipment. Those are all good and useful things. My roof is covered with solar panels and my garage has housed a hybrid since the first year they were available. My daughter calls me the Dark Lord for my light-dousing habits.


But you can’t make the math work one light bulb at a time. If Hansen is correct-and Hansen is the guy who first told Congress, 20 years ago this June, that global warming was real-then we don’t have time for a series of individual switches to add up to the kind of change we need. Instead, we need change from the top. We need a federal, and then an international, agreement to put a price on carbon, so that markets can go to work. If we were paying a price for all that CO2, then everyone would quickly be learning to conserve. Earlier this year, when an Alaskan utility line was snapped in a slide and prices soared, people in Juneau cut their consumption 30 percent in a week.


How do we get that kind of change? How do we overcome the power of the fossil fuel lobby? Only by building a real political movement. We did that last year in the U.S., when a few of us spearheaded Step It Up, which organized 2,000 demonstrations in all 50 states. That persuaded Barack Obama and Hillary Clinton to promise they’d meet our demand: 80 percent emission cuts by 2050.


But even if that happens, we still need to reach an international agreement, and soon. The nations of the world meet in Copenhagen in December 2009 to hammer out a treaty that will replace the expiring Kyoto Protocols.


That’s why we’ve formed 350.org, the first real attempt at a grassroots global climate movement. Our website works in 14 languages, and it’s already been used to organize demonstrations and rallies on every continent. We’ve had 350 surfers on the beach at Maui, and 350 bicyclists circling the Utah Statehouse. Some of our greatest outdoor athletes have already signed up for Team 350, spreading the word.


Our only real goal is to take that number, 350, and spread it everywhere on earth; to tattoo it onto every human brain. If we manage to do that, then there’s a chance that we can nudge those international negotiations in the direction of the science, in the direction of real change.


Please help. Come to 350.org. Organize an action. Put the number on the breast pocket of your next fleece. Stick it in the corner of your ads. Join in. You happen to be alive at the moment the world is coming apart, but if we work together fast, we have a chance to hold it together.