Natural Resources and the Environment - Dot Earth Blog - NYTimes.com
December 28, 2011, 1:13 pm
More Views on Climate Risk and Arctic Methane
By ANDREW C. REVKIN
In trying to clarify what’s known, unknown and learnable about the possible contribution to global warming from vast methane deposits beneath Arctic seas, I reached out to a host of scientists working on this question. I also received a lot of reader input, as you can see from the comment threads in the string of posts on this important issue. Here’s a roundup of some additional views from the scientific community and one filmmaker focused on question:
Raymond T. Pierrehumbert, a climate scientist at the University of Chicago and contributor to Realclimate.org (and sometimes Dot Earth), sent this thought:
Regarding the methane time-bomb issue, I do understand the need to respond to unwarranted predictions of catastrophe. I’ve made responses of this type myself. For example I think that Jim Hansen is demonstrably wrong in his assertion that a Venus-type runaway greenhouse is a virtual certainty if we burn all the coal; he is right about almost everything and I greatly admire him, but he is wrong about this.
Countering an assertion like that has the unfortunate consequence that some people say, “Whew, ducked a bullet there,” and go on to think that the rest of the consequences of global warming don’t look so bad in comparison with turning into Venus, not remembering that a lot of those consequences can still be very bad indeed.
But the clathrate release problem is in a rather different category from the runaway greenhouse issue. It has to be seen as just one of the many fast or slow carbon catastrophes possibly awaiting us, in a system we are just groping to understand. The models of destabilization are largely based on variants of diffusive heat transport, but the state of understanding of slope avalanches and other more exotic release mechanisms is rather poor — and even if it turns out that rapid methane degassing isn’t in the cards, you still do have to worry about those several trillion metric tons of near-surface carbon and how secure they are. It’s like worrying about the state of security of Soviet nuclear warheads, but where you have no idea what kind of terrorists there might be out there and what their capabilities are — and on what time scales they operate.
Edward Brook, a climate scientist and geochemist at Oregon State University, sent a comment as part of a group e-mail exchange that included this relevant thought:
One problem with this discussion is that there is no definition of “time bomb” so people get confused. It seems quite likely that continued global warming will increase the emissions of methane from permafrost deposits and marine hydrates. Some of that will get in to the atmosphere, though … some will also be consumed in the water column and in soils. This “chronic” source may increase over time, and affect climate, but for the reasons you discussed it is likely to be slow, and not a catastrophic risk. Of course it is still important. For a somewhat dated view of this topic, see [link].
Gary Houser, an environmental writer and producer of a documentary that’s being made about Arctic methane, sent a rebuttal of my initial post in this string, “Methane Time Bomb in Arctic Seas – Apocalypse Not.” Here’s an introductory riff and link to his full piece:
As co-producer of an upcoming in-depth documentary on the methane issue, I am stunned at how Revkin has dismissed the concerns of those trying to alert the world to the danger of a methane runaway feedback. It is one of the scenarios most feared by climate scientists. Once triggered, an abrupt downward spiral could ensue which humanity might be helpless to stop. When the factors which could unleash a runaway are beginning to line up, it is a time for humanity to take a pause from its many distractions and look.
Revkin’s search for unequivocal “evidence” that such “runaway disruption” is already underway ignores the key danger we face. If humanity waits until this level of “proof” is obtained, it will very likely be far too late to stop the colossal forces that will already be in motion.
In my full counterpoint, I present seven major reasons why the situation is one of great urgency. They are listed below. I urge the reader to please consider my more complete statement.
1) A force that has already demonstrated its awesome power during earlier periods on Earth-
2) Grasping the meaning of “irreversible” runaway train-
3) Insistence on “evidence” trumped by need to act preventatively-
4) The factors present which could launch a “runaway”-
5) The creation of a collision course toward methane release-
6) A classic moment to invoke the precautionary principle-
7) An immediate need to escalate a scientific inquiry of methane-
Read the full piece here.
Richard B. Alley, the climate scientist and ice sheet prober at Pennsylvania State University (and host of the PBS series “Earth: The Operators’ Manual“), wrote this: Read more…
Leaders of Arctic Methane Project Clarify Climate Concerns - NYTimes.com
January 4, 2012, 5:18 pm
‘Much Ado About Methane’
By ANDREW C. REVKIN
David Archer, the author of “The Long Thaw” and a Realclimate.org contributor, has weighed in at length on questions and assertions about the greenhouse risk posed by methane released from warming Arctic seabeds and tundra.
Josh Haner/The New York Times
In an Alaskan lake, bubbles of methane, a potent greenhouse gas, collect beneath the ice. More Photos
I encourage you to have a look in relation to the string of recent posts here aiming to restore some scientific weight to an overheated debate that has even led one online community, the Arctic Methane Emergency Group, to call for urgent geoengineering countermeasures.
Here’s one excerpt and a link to the rest of the piece, which concludes, as many climate scientists do, that CO2, not CH4, remains the key target if the goal is limiting disruptive greenhouse warming:
The possibility of a catastrophic release is of course what gives methane its power over the imagination (of journalists in particular it seems). A submarine landslide might release a Gigaton of carbon as methane (Archer, 2007), but the radiative effect of that would be small, about equal in magnitude (but opposite in sign) to the radiative forcing from a volcanic eruption. Detectable perhaps but probably not the end of humankind as a species.
What could happen to methane in the Arctic?
The methane bubbles coming from the Siberian shelf are part of a system that takes centuries to respond to changes in temperature. The methane from the Arctic lakes is also potentially part of a new, enhanced, chronic methane release to the atmosphere. Neither of them could release a catastrophic amount of methane (hundreds of Gtons) within a short time frame (a few years or less). There isn’t some huge bubble of methane waiting to erupt as soon as its roof melts.
And so far, the sources of methane from high latitudes are small, relative to the big player, which is wetlands in warmer climes. It is very difficult to know whether the bubbles are a brand-new methane source caused by global warming, or a response to warming that has happened over the past 100 years, or whether plumes like this happen all the time. In any event, it doesn’t matter very much unless they get 10 or 100 times larger, because high-latitude sources are small compared to the tropics. [Read the rest.]
In case you missed it, there’s more on the seabed methane emissions from Justin Gillis on the Green blog and an analysis of methane media coverage by Charles Petit at the Knight Science Journalism Tracker and another by Curtis Brainard at the Columbia Journalism Review