Seven facts you need to know about the Arctic methane timebomb
Dismissals of catastrophic methane danger ignore robust science in favour of outdated mythology of climate safety
5 August, 2013
Debate over the plausibility of a catastrophic release of methane in coming decades due to thawing Arctic permafrost has escalated after a new Nature paper warned that exactly this scenario could trigger costs equivalent to the annual GDP of the global economy.
"There is no evidence that methane will run out of control and initiate any sudden, catastrophic effects."
1. The 50 Gigatonne decadal methane pulse scenario was posited by four Arctic specialists, and is considered plausible by Met Office scientists
"Extremely high concentrations of methane (up to 8 ppm) in the atmospheric layer above the sea surface along with anomalously high concentrations of dissolved methane in the water column (up to 560 nM, or 12000% of super saturation)."
"Since the area of geological disjunctives (fault zones, tectonically and seismically active areas) within the Siberian Arctic shelf composes not less than 1-2% of the total area and area of open taliks (area of melt through permafrost), acting as a pathway for methane escape within the Siberian Arctic shelf reaches up to 5-10% of the total area, we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. That may cause ∼12-times increase of modern atmospheric methane burden with consequent catastrophic greenhouse warming."
"about 1.85 parts per million, the highest in 400,000 years" and "on par with previous estimates of methane venting from the entire World Ocean."
2. Arctic methane hydrates are becoming increasingly unstable in the context of anthropogenic climate change and it's impact on diminishing sea ice
"Large volumes of methane in gas hydrate form can be stored within or below the subsea permafrost, and the stability of this gas hydrate zone is sustained by the existence of permafrost. Degradation of subsea permafrost and the consequent destabilization of gas hydrates could significantly if not dramatically increase the flux of methane, a potent greenhouse gas, to the atmosphere."
"... causing the liberation of methane from decomposing hydrate... If this process becomes widespread along Arctic continental margins, tens of Teragrams of methane per year could be released into the ocean."
"... 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."
"... in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap."
3. Multiple scientific reviews, including one by over 20 Arctic specialists, confirm decadal catastrophic Arctic methane release is plausible
"... while many deep hydrate deposits are indeed stable under the influence of rapid seafloor temperature variations,shallow deposits, such as those found in arctic regions or in the Gulf of Mexico, can undergo rapid dissociation and produce significant carbon fluxes over a period of decades."
"The time scales for destabilization of marine hydrates are not well understood and are likely to be very long for hydrates found in deep sediments but much shorter for hydrates below shallow waters, such as in the Arctic Ocean... Overall, uncertainties are large, and it is difficult to be conclusive about the time scales and magnitudes of methane feedbacks, but significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out... The risk of a rapid increase in [methane] emissions is real but remains largely unquantified."
"The [ESAS] is a powerful supplier of methane to the atmosphere owing to the continued degradation of the submarine permafrost, which causes the destruction of gas hydrates. The emission of methane in several areas of the [ESAS] is massive to the extent that growth in the methane concentrations in the atmosphere to values capable of causing a considerable and even catastrophic warning on the Earth is possible."
4. Current Arctic methane levels are unprecedented
"IASI data for the autumn months (October-November) clearly indicate Eurasian shelf areas of the Arctic Ocean as a significant methane emitter. The maximal methane concentrations were found over Kara and Laptev Seas. According to IASI data, during the last three years in autumn time, methane over Eurasian shelf has been increased by 25 ppb, over the N. American shelf, by 23 ppb, and over the land between 50 N and 70 N for both Eastern and Western hemispheres, by 20 ppb."
5. The tipping point for continuous Siberian permafrost thaw could be as low as 1.5C
6. Arctic conditions during the Eemian interglacial lasting from 130,000 to 115,000 years ago are a terrible analogy for today's Arctic
"... the key distinction is that the warming today is from Greenhouse gases being higher and occurs 'twenty-four seven', namely the cooling at night is much less (diurnal variation smaller); in the Eemian the tilt of the Earth was much greater so there was much more seasonality, thus winters were much colder so the sea ice extent, thickness, and thus volume could build up much more, and the summers were warmer in the daytime, however the cooling at night was much greater than now (less greenhouse gas [GHG], more diurnal variation); net result is that the ice was much more durable in the Eemian. Greenland temps were higher during the daytime, but cooled off much more during the nighttime in the lower GHG concentration world."
7. Paleoclimate records will not necessarily capture a large, abrupt methane pulse
"The length of time for the methane pulse is very important here. If most of the methane came out in a decade, for example then within a subsequent decade or so most of the methane will have been broken down to CO2 and H20 and also been dispersed/distributed around the planet, away from the pulse source area in the Arctic. The CO2 produced would have been small (CO2 stayed within 180-280 ppm range). It takes about 50 years or even more (depending on the snowfall rate and surface melt rates) for snow at the surface to be compacted into firn that closes off the air spaces creating the bubbles in the ice that are reservoirs of the methane and other atmospheric gases. Because of that 50 year bubble closure time, the large pulse of methane that was burped out of the marine sediments and terrestrial permafrost would be long gone and not result in a detectable signal in the ice core record. Just because the record does not capture it does not mean that it was not produced."