Carbon dioxide isn't the only greenhouse gas out there. Other substances, such as water vapor and nitrous oxide, also trap heat to varying degrees. Discussions about global warming focus on CO2 for a couple of key reasons: the first is that human activities have demonstrably increased carbon dioxide; the second is that the other gases tend to cycle out of the atmosphere pretty quickly. For the most part, unless there's a sudden, massive increase in the amount of the other greenhouse gases, we can safely focus on CO2.
Well, guess what?
Scientists from Alaska's International Arctic Research Center, the Russian Academy of Sciences, and Stockholm University have published an article in Science magazine indicating the discovery of a startlingly large amount of methane coming from the East Siberian Arctic Shelf—methane that was thought to be frozen, in the form of methane clathrates. How much methane? An amount equivalent to the total of methane coming from the rest of the world's oceans. The key paragraph, from the National Science Foundation press release:
They found that more than 80 percent of the deep water and more than 50 percent of surface water had methane levels more than eight times that of normal seawater. In some areas, the saturation levels reached more than 250 times that of background levels in the summer and 1,400 times higher in the winter. They found corresponding results in the air directly above the ocean surface. Methane levels were elevated overall and the seascape was dotted with more than 100 hotspots. This, combined with winter expedition results that found methane gas trapped under and in the sea ice, showed the team that the methane was not only being dissolved in the water, it was bubbling out into the atmosphere.
Okay, it's a lot of methane... so what?
Methane—CH4—actually traps a significantly greater amount of heat than does CO2. The NSF article cites it as 30 times greater greenhouse impact than carbon dioxide, and I've seen references between 20x and 72x, depending upon how it's measured. Regardless, this is a big difference, and the amount of methane frozen under the Siberian permafrost can be measured in the millions of tons (up to 70 billion tons across the entire permafrost region). If the East Siberian methane melts, it would be akin to tripling the amount of CO2 in the atmosphere, raising temperatures around the world by 8-10° C, and arctic temperatures by 20° C by the end of this century. That would be very, very bad, like you-really-don't-want-to-go-there bad.
You see, the East Siberian methane is fairly close to the surface; as temperatures rise, methane clathrates deeper down will start to melt, making temperatures go up faster, melting even deeper stores of methane ice, and so on. It's a runaway feedback loop—what some folks call the "clathrate gun." This whole process would take just a few decades. Melting methane clathrates are pretty much the scariest of the so-called "tipping point" effects of anthropogenic global warming. We don't need to burn every fossil fuel on the planet to make something awful happen, we just have to burn enough to start to thaw out methane ice, and natural processes take it from there.
There are two immediate questions we need to answer:
1) Does this study show us that there's a runaway methane event underway? The short answer is no. This is the first detailed study of methane concentrations in the region, so we don't know for sure whether the methane concentrations are increasing slowly, increasingly quickly, or not increasing at all. That the amount of methane is so disproportionate (and is higher than amounts found in ice core samples from thousands of years ago) suggests that something is happening, but in my expert opinion, it's not yet time to panic.
2) What can we do about it? It depends on how fast the methane clathrates are melting. If they're melting slowly, our best bet would be to do everything humanly possible to cut anthropogenic carbon emissions to zero. We have to avoid pushing the climate into a runaway methane tipping point; the faster we cut our carbon emissions, the better chance we have of avoiding this catastrophe.
If the methane clathrates are melting quickly, however, the story gets more complicated. Although we'd want to get to zero as quickly as we could, because of the carbon we've already put into the atmosphere—which keeps warming us—and because of ocean thermal inertia—the pace at which the ocean warms up and cools down—we'd still see another few decades of warming. Simply going to zero wouldn't be enough to avoid a methane runaway, if the clathrates are already melting quickly.
This is where the desperation moves come in. It's quite likely that, for many people, a clathrate melt would mean geoengineering goes from being a "Plan B" to "Plan Ohmygodyouhavetostartdoingthisnow." At the very least, we would need to step up the study of how temperature-management geoengineering would affect the overall environment, because there's a very good chance we'll want to use it.
We also would want to look at ways to remove the methane from the oceans and the atmosphere. I have a long post over at my main blog detailing what this would entail, but it's enough to say here that while it wouldn't be easy, it looks like it might be possible. This would have its own side-effects, too, of course... but probably not as bad as a mass extinction event.
The big lesson here is that the Earth's environment is a fantastically complex system, and changing one parameter—in this case, the temperature—can have effects far beyond what a simple straight line extrapolation would suggest. If we're lucky, follow-up studies will show that the methane emissions are either stable or only growing slowly, giving us enough time to upgrade how we live without having to do anything risky. But even if this is the case, good luck can't hold on forever.