350 is the most important number in the world—it's what scientists say is the safe upper limit for carbon dioxide in the atmosphere.
Two years ago, after leading climatologists observed rapid ice melt in the Arctic and other frightening signs of climate change, they issued a series of studies showing that the planet faced both human and natural disaster if atmospheric concentrations of CO2 remained above 350 parts per million.
Everyone from Al Gore to the U.N.’s top climate scientist has now embraced this goal as necessary for stabilizing the planet and preventing complete disaster. Now the trick is getting our leaders to pay attention and craft policies that will put the world on track to get to 350.

As we currently are at 387 ppm in the atmosphere, we have some work to do in order to get things into the minimally safe upper limit. The next question of course would be: How do we do that? McKibben's group's theory is that we do it by creating the political change to steer us toward 350 FAST. His grassroots movement is all about an international holding of feet to the fire (pun quite intentional) to use Copenhagen to produce a treaty that is strong, equitable and grounded in the latest science.

I've been working on this post since yesterday, and this morning came this email from McKibben and company, one last prod to keep me from wanting to sleep in tomorrow morning instead of joining one or more of the many events planned right here in New Mexico:

Dear Friend,
Saturday's the day -- October 24, the International Day of Climate Action. So join the nearest 350 action knowing you'll be part of something big.
Very big, in fact. This campaign has gone viral--there will be over four thousand events taking place simultaneously in over 175 nations. As far as we can tell, you'll be part of the single most widespread day of political action about any issue that our planet has ever seen.
There are too many incredible events to list in one place, but here are some of the highlights:
In Cambodia, citizens from across the country will gather at the famous Angkor Wat to take a giant 350 action photo.
In Hungary, hundreds of bathers will jump into the public baths in Budapest and do a 350 synchronized swimming performance.
In Nepal, over a thousand young people and monks will march to the Swayambhunath world heritage site temple where they will form a large 350 with traditional lanterns.
In the United States, 350 people will dance to Michael Jackson's Thriller in Seattle -- because if we don't stop global warming, we might as well be undead.
In Panama, indigenous youth will lead a moonlight vigil in Kuna Yala, their vulnerable low-lying islands off the coast of Panama, forming a 350 at sunrise.
When you're out there marching or rallying, biking or kite-flying, singing or taking part in whatever is going on in your community, take a minute and try to imagine all the other people doing the same kind of things all around the world--every one taking the same basic scientific fact and driving it into the public consciousness.
350 is the most important number in the world--scientists have told us that it's the most carbon dioxide we can have in the atmosphere, and now we're making sure everyone knows. We'll be taking photos from all the events, projecting them on the big screens in New York's Times Square, and delivering them to major media outlets and hundreds of world leaders in the coming weeks. The combined noise from these events will ensure that world leaders who gather next month at the UN climate talks in Copenhagen to create the world's new plan on climate change will hear our call. They will know that when negotiating the fate of our planet, there is a passionate movement out there which will hold them accountable.
After your event on Saturday, check out http://www.350.org/, where we will show a glorious slideshow of photos from events in every corner of the earth. Be proud of what you've accomplished.
And if you have any doubts about where the fun in your neighborhood is on Saturday, check out this link to find an event near you: http://salsa.democracyinaction.org/dia/track.jsp?v=2&c=NOCZi%2F44zIu8FiHjPF2EK15WuoA8ncEL
Onwards,
Bill McKibben for the 350.org crew

There's bound to be something happening where you are, please please please check it out and be part of this very creative demonstration. Everything you care about may depend upon it.

(Crossposted at Quid Nunc)