Poster's note - the 'Arctic methane emergency' has been a component of the arguments of the most vocal CE proponents for some time. This review challenges that framing, and appears to conclude that it's a distraction from the CO2 issue.
http://www.newscientist.com/article/mg22630221.300-methane-apocalypse-defusing-the-arctics-time-bomb.html?full=true#.VWCyQXnbLIU (£) Extract There is, then, no solid evidence to back the idea of a methane bomb and past climate records suggest there is no cause for alarm. "Is it right to be alarmist? Is it right to be too conservative? There are problems with both, so you want to get it right," says Crill. "Extraordinary claims require extraordinary proof, otherwise it's going to undermine credibility and slow down our ability to actually make the decisions that we are going to have to make as a society." No one is saying methane is not a concern. Levels are now the highest they've been for at least 800,000 years and climbing. The Intergovernmental Panel on Climate Change's worst-case emissions scenario does assume a big rise in methane, to as much as 4000 ppb by 2100. This scenario does not include some possible positive feedbacks, such as increases in methane emissions from wetlands if local water tables rise and if warming boosts microbial activity. This could lead to an additional rise of around 800 ppb, Schmidt's team estimates. So methane is seen as significant – just not apocalyptic. What about the gaping craters? They are certainly spectacular and scary-looking. The latest idea is that they are caused by the release of pockets of compressed methane as ice seals melt. But the amount of methane released per crater is minuscule in global terms. Around 20 million craters would have to form within a few years to release 50 gigatonnes of the gas, Archer has calculated. Far from being a sign of the methane apocalypse, the craters are a distraction from the real problem – the continuing massive emissions of CO2 from burning fossil fuels. CO2 levels are rising faster than ever. As a result, we're currently on course for warming of between 3 °C and 5 °C, or more, even without a methane bomb. And despite all the talk about reductions, the omens are not good. We've already discovered far more fossil fuel than we can afford to burn, but as yet not a single country has any plans to leave any of it in the ground. Now that really is scary. This article appeared in print under the headline "The methane apocalypse" Anil Ananthaswamy is a freelance writer based in Berkeley, California -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
