The answer is in part in the enclosed article.
Methane increased from about 700 ppb to about 1800 ppb since about 1800 AD – we have few examples for such sharp rise since about 55 million years ago.
Transient cooling due to cold ice melt water and the La-Nina temporarily slows down CO2 and CH4 release.
Of course the pro-carbon lobby will use any irregularity in the multi-decadal trend to justify their false claims.
Andrew
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METHANE AND THE ANTARCTIC ICE SHEET.docx.pdf 367K View Download |
28-2-2012
December 14, 2011, 5:43 pm
Methane Time Bomb in Arctic Seas – Apocalypse Not
By ANDREW C. REVKIN NEW YORK TIMESDec. 19, 1:44 p.m. | Updated below |
A very important research effort has been under way during recent summers in the warming, increasingly ice-free shallows off Russia’s Siberian coast. There, an international array of scientists has been investigating widening areas of open water that are disgorging millions of tons of methane each year.
Given that methane, molecule for molecule, has at least 20 times the heat-trapping properties of carbon dioxide, it’s important to get a handle on whether these are new releases, the first foretaste of some great outburst from thawing sea-bed stores of the gas, or simply a longstanding phenomenon newly observed.
If you read the Independent of Britain, you’d certainly be thinking the worst. The newspaper has led the charge in fomenting worry over the gas emissions, with portentous, and remarkably similar, stories in 2008 and this week. [Dec. 29, 1:44 p.m. | Updated | Steve Connor, the writer (also science editor) at The Independent, alerted me that the article has been revised with a new headline and expanded to include content that didn’t make it into the piece when first published.]
If you read geophysical journals and survey scientists tracking past and future methane emissions, you get an entirely different picture:
A paper published in Dec. 6 in the Journal of Geophysical Research appears to confirm pretty convincingly that the gas emissions seen in recent years are from a thawing process that has been under way for 8,000 years — since seas rose sufficiently to cover the near-shore seabed. Sharp warming of the sea in the region since 1985 has clearly had an influence on the seabed, according to the paper, led by Igor Dmitrenko of the Leibniz Institute of Marine Sciences in Kiel, Germany.
But read this summary of the paper from the American Geophysical Union, which publishes the journal, and see if you feel reassured that the “methane time bomb” there is safe for a long time to come:
[T]he authors found that roughly 1 meter of the subsurface permafrost thawed in the past 25 years, adding to the 25 meters of already thawed soil. Forecasting the expected future permafrost thaw, the authors found that even under the most extreme climatic scenario tested this thawed soil growth will not exceed 10 meters by 2100 or 50 meters by the turn of the next millennium. The authors note that the bulk of the methane stores in the east Siberian shelf are trapped roughly 200 meters below the seafloor… [Read the rest.]
Here’s the link to the paper itself: “Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability.”
To review, the authors confirm “drastic bottom layer heating over the coastal zone” that they attribute to warming of the Arctic atmosphere, but conclude that “recent climate change cannot produce an immediate response in sub-sea permafrost.” That’s the understatement of the year considering their conclusion that even under sustained heating, the brunt of the sub-sea methane won’t be affected in this millennium.
It’s worth considering the risks of “single-study syndrome,” given that other recent work continues to find disturbing amounts of methane emissions in Arctic shallows.
But scientists who track methane in the atmosphere in the Arctic and elsewhere around the planet see no big surge that can be pinned on such releases. Before I distributed the link to the new paper above to relevant scientists, I’d already heard from Ed Dlugokencky, one of the top federal researchers tracking methane trends. He sent a detailed review of atmospheric measurements from the Arctic to the Equator and concluded, quite simply:
[B]ased on what we see in the atmosphere, there is no evidence of substantial increases in methane emissions from the Arctic in the past 20 years.
This all builds on what I was told in 2010, when I last visited the question of methane releases from Arctic seas. (There’s an entirely different set of questions, also with relatively reassuring answers, about the vast amounts of methane locked in permafrost on land.) I urge you to read, and pass around, the 2010 post — “The Heat Over Bubbling Arctic Methane.”
So the next time you see a “science stunner” about Arctic methane time bombs, reach out to a couple of scientists working on this gas before you run to the ramparts.
