Updated, July 26, 9:45 a.m. |
Jason Samenow’s posts at the Capital Weather Gang blog are always valuable reading. But he has outdone himself with a new piece helpfully laying bare the glaring problem at the heart of a much-discussed commentary in this week’s issue of Nature calculating how many trillions of dollars in economic costs would attend a burst of methane emissions from the warming Arctic.
Here’s an excerpt from his critique:
Methane mischief: misleading commentary published in Nature
A catastrophic release of the potent greenhouse gas methane in the Arctic could cause a sudden warming with massive economic consequences says a commentary published in the esteemed scientific journal Nature Wednesday. Yet most everything known and published about methane indicates this scenario is very unlikely. This piece should never have been published without discussing this critical point.
Samenow adds this devastating detail:
Nature, the same journal which published Wednesday’s commentary, published a scientific review of methane hydrates and climate change by Carolyn Ruppel in 2011 which suggests the scenario in said commentary is virtually impossible. The review states:
Catastrophic, widespread dissociation of methane gas hydrates will not be triggered by continued climate warming at contemporary rates (0.2ºC per decade; IPCC 2007) over timescales of a few hundred years. Most of Earth’s gas hydrates occur at low saturations and in sediments at such great depths below the seafloor or onshore permafrost that they will barely be affected by warming over even [1,000] yr.
[Update, July 26, 9:45 a.m. | Peter Wadhams, an author of the Nature commentary, has posted a response to Samenow’s piece.]
Gavin Schmidt of NASA and the Realclimate blog, which has provided repeated reality checks on the Arctic methane question, did what he could on Twitter to push back, posting repeatedly on the implausibility of the methane pulse scenario [this is an updated Twitter string added since initial post]:
@elmarveerman @karelh @BVerheggen threshold releases even 1/10 as lg as postulated would be clear in ice cores. There is nothing there.
I encourage you to look at the entire string from Schmidt from which I extracted this sequence:
9) in more recent past, there have been a number if times when Arctic (not necessarily globe) has been significantly warmer than today.
10) Most recently, Early Holocene, which had significantly less summer sea ice than even 2012. Earlier, Eemian 125kyrs ago was sig warmer
11) At neither of these times is there any evidence for CH4 emissions or concentrations in excess of base pre-industrial conditions.
12) this means that we are not currently near a threshold for dramatic CH4 releases. (Though we may get there)
13) Much of the concern re dramatic changes in Arctic methane come from one off surveys and poorly calibrated remote sensing
14) thus potential for Arctic CH4 to have threshold behaviour is real, but very lg scenario used in Nature comment is not realistic
There are other climate zombies roaming the world, as Richard Alley of Pennsylvania State University has explained.
This one will continue to rise from the Arctic, I’m sure, no matter how many times scientists remind people about the lack of evidence that such an outburst is plausible.
Updated, Aug. 2, 11:40 a.m. | It’s encouraging to see Michael Tobis at Planet 3.0 weigh in:
I have some knowledge in this field. Wadhams’ and Shakhova’s claims are incoherent and implausible; for practical purposes there remains no evidence of the purported massive emission.
Updated, Aug. 21, 1:41 p.m. |
In the Guardian, Nafeez Ahmed has renewed his effort to mainstream the idea that methane outgassing from subsea permafrost is of global concern.