A methane scoping questionSeptember 23, 2008 at 11:51 am | Posted in Climate change, Environment, Global warming | 5 Comments
Tags: Arctic, Carbon dioxide, CH4, Climate change, CO2, Context, GHG emissions, Greenhouse gases, GWP, Melting, Methane, Permafrost
Can any climate scientist knowledgable on the significance of Arctic sub-sea methane release put today’s Independent Front Page ‘Exclusive: The methane time bomb‘ into context for me, please? It is a perspective on the scale of today’s news that would be good to have. Just because the intensity of release in certain areas is high and millions of tonnes of methane are being released, does not mean that this is as significant as implied by the article, nor that such releases have not already been catered for in model scenarios. Although, when I read on RealClimate Ray Ladbury’s comment dated 18 May 2008:
There is evidence for positive feedback that is not in the models (e.g. outgassing from thawing permafrost, oceans, etc.)
it makes me wonder how to begin to quantify today’s news (while acknowledging this information has been released in mainstream media before preliminary findings are published in AGU literature).
Here are a couple of quotes:
Orjan Gustafsson of Stockholm University in Sweden, one of the leaders of the expedition, described the scale of the methane emissions in an email exchange sent from the Russian research ship Jacob Smirnitskyi.
“We had a hectic finishing of the sampling programme yesterday and this past night,” said Dr Gustafsson. “An extensive area of intense methane release was found. At earlier sites we had found elevated levels of dissolved methane. Yesterday, for the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface. These ‘methane chimneys’ were documented on echo sounder and with seismic [instruments].”
The preliminary findings of the International Siberian Shelf Study 2008, being prepared for publication by the American Geophysical Union, are being overseen by Igor Semiletov of the Far-Eastern branch of the Russian Academy of Sciences. Since 1994, he has led about 10 expeditions in the Laptev Sea but during the 1990s he did not detect any elevated levels of methane. However, since 2003 he reported a rising number of methane “hotspots”, which have now been confirmed using more sensitive instruments on board the Jacob Smirnitskyi.
Steve Connor did a parallel backgrounder here:
Although I don’t like the use of ‘ultimate’—as it implies finality—nor am I keen on the überscary word ’dreaded’ in the title, I accept, with a sigh, that headlines are written to grab attention in the hope that some people read beyond …
Anyway, methane emissions are hardly on the radar screens of most policymakers or businessmen, as far as I am aware. There is not a lot they can do about it, but with headline stories like this, if methane has the potential to wreak havoc on a large scale, and significant climate change seems inevitable, people will perhaps ask “Why bother trying to reduce carbon emissions?” Context would help …
If radiative forcing is used to measure climate impacts of GHGs, the total methane contribution to warming to date appears to be less lethal compared with the total contribution from carbon dioxide, which accounts for three times the warming so far. According to wiki, methane concentrations have increased 150% since industrial revolution, giving an RF of +0.48 W/m2, while carbon dioxide concentrations have increased 38% to give RF of +1.46 W/m2.
Steve Connor is underestimating the power of methane when he says it is about 20 times more potent than carbon dioxide as a greenhouse gas: it has a century-timescale global warming potential (GWP) of 23, but the relevant figure for its potency in the first 20 years after its release is 62, dropping to 23 over 100 years, and 7 over 500 years.
Some of that CH4 gets converted to CO2 along the way, but the point is that for the same mass of gas, methane packs 62 times the punch of carbon dioxide in the first two decades after its release into the atmosphere. This is obviously not good if we consider targets for reducing CO2 emissions by 2020, 2030 or even all the way to 2050, as methane has the ability to increase the greenhouse effect dramatically sooner and add to the long-lasting carbon dioxide concentrations later.
I just wonder how climate scientists would frame an answer to members of the public who noticed the front page methane story in today’s Independent newspaper and who want to, somehow, gauge its significance.
P.S. Two days later, and Steve Connor has another story about methane bubbles from the Arctic seabed, this time discovered by British research scientists near the Norwegian island, Svalbard: