Catastrophic Arctic methane release feedback?

NewImageThere is high concern in some quarters about the possibility of near-term catastrophic Arctic methane release. Example: the Arctic Methane Emergency Group which promotes videos such as Arctic Methane: Why the Sea Ice Matters. I’ve reviewed the recent peer-reviewed publications via Google Scholar, concluding that near-term (decades) disaster is extremely unlikely. The potential for long-term (centuries) feedback remains one of many climate change risks that we just don’t know much about. The current climate forcing is so much faster than anything seen in the geologic record — we are definitely exploring new territory.

A good summary of what I’ve learned can be found in this post at the Arctic Methane blog by Prof. Euan Nisbet. Here’s a brief excerpt that addresses the recent media-frenzy prompted by the Guardian articles (which stemmed from the Whiteman paper).

Is Godzilla about to arise? Is there a methane monster?

In the 25th July issue of Nature this year, Whiteman et al. suggested a monster methane release is about to occur in the Arctic. They modelled a release of 50 Giga-tons of methane from Arctic hydrate, at 5 Gt a year over 10 years from 2015 to 2025. One Giga-ton is 1000 million tons, or 10^15 grams. To put this in context, the total amount of methane in the world’s air now is about 5 Gt, and the annual input is about 0.5 Gt, so this would double the methane in the air within the first year. They based this number on a ‘single stage blowout’ scenario from another paper by Shakhova et al, (2010). The Whiteman et al. paper had immediate press interest, from newspapers as prestigious the Guardian and the New York Times to a wide range of blogs.

Contrary voices were also heard, in particular from researchers on methane and hydrates (including the present author). They were widely sceptical of such large releases. Responses were both published later in Nature, and also a posted comment that is accessible by scrolling far down the page on:

http://www.nature.com/nature/journal/v499/n7459/full/499401a.html

The full text is on:

http://equianos.com/wordpress/wp-content/uploads/Response-to-Whiteman_et-al-Comment.pdf

There’s clearly a great deal of methane hydrate in the Arctic, and much of it is likely to be destabilised by Arctic warming. But is it going to come out as a great sudden burst in a few years? Or is it going to dribble out as a chronic release, as suggested in 2008 by David Archer, a recognised hydrate expert? Remember also that the northern wetland methane emissions respond very fast to warming. There’s much evidence that at the end of the last glaciation it was not primarily the hydrates but the wetland response that drove the very rapid increase in methane.

Archer, et al (2008) Ocean methane hydrates as a slow tipping point in the global carbon cycle, Proc. Natl. Acad. Sci. 106, 20596–20601

Nisbet, E.G. and Chappellaz, J., (2009) Shifting gear, quickly. Science 324, 477-8

The scepticism of Arctic researchers about the 50 Gt blowout scenario was initially dismissed by an influential Guardian blog as “narrow arguments of scientists out of touch with cutting edge developments in the Arctic.” http://www.theguardian.com/environment/earth-insight/2013/aug/05/7-facts-need-to-know-arctic-methane-time-bomb

However, later the comment was modified:

http://planet3.org/2013/09/05/nafeez-ahmed-responds/#comment-40721

The answers to these puzzles is what we’re trying to find out….

Dr. Nisbet’s post is written for the lay public – highly recommended. To repeat, Dr. Nisbet and colleagues wrote a detailed response in Nature to the Whiteman et al paper. Nisbet mentions this in his blog post — so politely that it may not to be noticed.