In the run up to Copenhagen even supermodels are jumping into the fray. There is a new viral video (700,000 views in just over 10 days) in which some supermodels “strip for climate change” on behalf of Bill McKibben‘s new outfit 350.org. How exactly this video will assist in mitigating greenhouse gas emissions or in getting us back to 350 ppm is not entirely clear. (but I suppose the same could be said about our blog)
Ove and Charlie Veron discussed the importance of getting back to 350 ppm here; The coral reef crisis: The critical importance of <350 ppm CO2
The utility and some of the nuances of the 350 concept, e.g., how soon do we need to get back there, have become a bit controversial within certain AGW circles. Witness this dust up among AGW blogosphere titans Bill McKibben, Andrew Revkin and Gavin Schmidt (click on the comments and read comments #3-5). Also see this view of the idea and campaign by Dr. Ray Pierrehumbert, a University of Chicago climate scientist (and fearless debunker of the rubbish about climate change being peddled by Steve Levitt):
Hansen’s specific reasoning behind 350 was based largely on an estimate of the CO2 level when Antarctic glaciation started, plus a bit of margin of safety thrown in. There is a lot of uncertainty regarding that CO2 level, but it is certainly an interesting line of thinking. One needs to recognize,though, that this specific argument for 350 involves relatively slow climate responses. It is unlikely that Antarctica would deglaciate if we exceeded 350 for just a decade or two. So, you have a bit of wiggle room on the overshoot, so long as the CO2 doesn’t stay above 350 for several hundred years (the precise duration where you get worried being contingent on aspects of the response time of ice sheets that are still poorly understood).
Now, the problem is the slow recovery time of atmospheric CO2 after you stop burning fossil fuels. But, what is certain is that if we go to 600 or 700, the CO2 could easily remain over 350 for a thousand years, which gives a long time for bad stuff to happen. So, the “350” goal may still be attainable if it is interpreted as meaning we have to keep the CO2 300 years out (say) from exceeding this value. – Dr. Ray Pierrehumbert via a comment on Dot Earth
Update (15/11/09); a reader emailed to ask how the “dust up” mentioned above could be found. It can be seen in the DotEarth story on the 350 movement (note the mildly critical comments by Gavin Schmidt, Andrew Revkin (the author), and Ray Pierrehumbert (above) and in articles on the 350 idea on why how we get back to 350 matters and on the Hansen paper much of this movement is based on on the Real Climate web site, and in the comments section of one of these articles. To make it really easy, ill paste some of the comments below:
I’d hoped to retain that great final line, but in the eternal space crunch, it got dropped.
The vital question, I’m told repeatedly by specialists in the non-science arenas you list (economics, technological change, politics), is what policies have the best shot of producing a peak and decline that limits climate risks as delineated by the science.
And most of those curves are quite similar no matter what end point is chosen, given the change required just to stablize at ANY concentration in a world heading toward 9 billion people seeking decent lives.
A couple of useful additional perspectives that didn’t fit in print were offered by Rajendra Pachauri of the IPCC (who endorsed the 350 campaign):
“We are dealing with a dynamic system. Hence, what would really be relevant is the trajectory of concentration levels and therefore emission trajectories. The 350 number has some appeal, because it would to some extent determine the peaking period and the rate of decline. Of course 350 by itself provides no solution. It would merely be the end point of a trajectory which theoretically can have infinite alternatives.”
And Mike Hulme, the British climate maven who wrote “Why We Disagree About Climate Change”:
“I never quite know what targets like 400, 350 or 280 mean…. If we mean stabilise back at 280 by 2200, say, then we can pump a lot of CO2 in the meantime, before some really good carbon scrubbing technologies in the 22nd century come along. Same argument actually for 280 by 2100 if you’re a technology optimist. So really if one wants to deal in long-term numbers then talk either about future C budgets (how many gigatons are you going to allow), or else set the peak concentration and by when. My guess is that for CO2 we will hit 500ppm sometime this century (harder to guess what CO2-equiv will be). On what to aim for – I wouldn’t play politics will long-term numbers: far too easy for them to be hijacked and used for all sorts of dubious reasons and causes. Much better is to focus on near-term goals (2015, 2020) and to break them down into manageable sectors (e.g. aviation, municipalities, aluminium sector, etc.). The rhetoric of global long-term targets raises the illusion that we can govern globally over the long-haul (the illusion of Copenhagen) – and we can’t.”
Many thanks to Gavin for his clarification, and for his work (and everyone else’s at RC) over the years. For whatever reason Andy chose to paint the 350 effort as unlikely in his story, but it was reported the day before we actually showed you could mobilize millions of people in 5200 events in 181 countries in what the press is calling ‘the mose widespread day of political action in the planet’s history,’ all around a scientific data point. I think tht should be heartening to all.
The biggest point the number gets across, i think, is that climate change is not some future threat but a present crisis. If you have a moment, I recommend browsing through the photos we’ve got up at 350.org (a tiny subset of the 21,000 now in our flickr photostream) to get a sense of the people who are waking up to this reality.
thanks to all who participated Saturday
Andy Revkin says:
Just one last thought here, upon reading Bill’s comment.
There were two things to report on (and my reporting continued through the actual day of action):
1) The amazing coordinated globe-spanning mosaic of actions
2) the basis for the focal point of that action.
On the first, there’s no question an epic effort was carried off with astonishing scope and skill.
On the second, there remain large, substantive and vital questions. As I said in a comment response somewhere on my blog, a keystone question is 350 by when? As Pachauri and others explained, 350 ppm on its own is kind of like judging a car’s mileage by “miles” without the “per hour.”
My story had to examine both the news and the context. We’ve been pilloried in the past for simply reporting what folks are saying without examining the evidence and argument. I’m not drawing ANY comparisons at all, but examples that come to mind are when a president pumps up the WMD threat, or when candidates rattle off jargon like “clean coal.”