IV. Arctic Permafrost and Methane

Another scare story coming out of the Arctic is that Arctic warming will release untold amounts of the potent greenhouse gas methane into the atmosphere from widespread melting of the Arctic permafrost. However, a douse of cold water was recently thrown to this alarmist scenario.

The alarmist theory of Arctic permafrost goes something like this.

Permafrost is a sink for carbon dioxide and other greenhouse gases such as methane. Basically, the soils of the high latitudes froze at the beginning of the last ice age, and when they froze, they entrapped very large amounts of organic material (carbon rich grasses, animal remains, soil material) in the frozen permafrost. As the permafrost thaws, carbon trapped within the once-frozen soils is released largely as methane, and as this methane is mixed into the global atmosphere it will cause even more warming which feeds back onto itself and causes more permafrost melting and more methane release and more warming.

The entire process is described by many as a time bomb that is going off before our very eyes. The bomb is not just causing the world to warm at a more rapid pace, but the melting permafrost is also routinely connected to the destruction of forests (recall Gore’s pictures of “drunken forests” in An Inconvenient Truth), collapse of homes and other structures (e.g., pipelines), erosion of coastal areas and hillsides, disruption of animal habitats, etc.

On this particular point, observations by Professor Syun-Ichi Akasofu, founding director of the International Arctic Research Center of the University of Alaska Fairbanks, are noteworthy:

[People] say permafrost is melting, and houses are collapsing. What happens is that, when permafrost is in the area, housing is cheap and the land is cheap. When people build a house directly over the permafrost, and then warm the house in the wintertime, and the ice underneath melts and the house collapses, that's a man-made effect! [sic.]

In addition, Gore’s methane bomb was recently factually defused in an article appearing in Geophysical Research Letters entitled “Near-surface permafrost degradation: How severe during the 21st century?” by Georg Delisle, a scientist from Germany’s Federal Institute for Geosciences and Natural Resources (the central geoscientific authority providing advice to the German Federal Government in all geo-relevant questions).

The final sentence of the abstract states “Based on paleoclimatic data and in consequence of this study, it is suggested that scenarios calling for massive release of methane in the near future from degrading permafrost are questionable.”

Delisle acknowledges that warming is occurring in the Arctic regions and that the warming will undoubtedly impact the permafrost of the high latitudes. The author notes, however, that many numerical models used to simulate the impact of warming on permafrost deal only with the upper 10 feet of the earth’s surface. The previously-used models do not take into account the cooling effect of deeper and colder zones that interact thermodynamically with the active layer near the surface. Delisle also exposes other assumptions of previous models that are “in clear conflict with field evidence.” In other words, the models driving lurid headlines and political anxiety get it wrong, again.

Delisle instead presents “a unidimensional long term permafrost temperature model of general application” “which is fully capable of incorporating all relevant thermal processes within the active layer and the permafrost, and between the permafrost and the non frozen ground below. The model space is made up of 600 layers with a minimum spacing of 10 cm within the active layer and the uppermost ‘permafrost zone’.” Rather than look at only 10 feet into the surface as was done by previous models, the new model goes 100 yards into the surface, and is deemed as more realistic.

With the improved model, Delisle reports that continuous permafrost in Alaska and Siberia will survive over the next 100 years, even if a significant warming takes place. Further, he states that “Based on this result and on the presented analysis, it appears that all areas north of 60°N will maintain permafrost at least at depth. North of 70°N, surface temperature values today are in general below -11°C. These areas should maintain their active layer. It appears unlikely that almost all areas with near-surface permafrost today will lose their active layer within the next 100 years” as concluded by others. Delisle claims that the new model is far more consistent with field measurements and far more realistic in terms of including the energy flux component from the deeper and colder core.

Delisle adds a zinger at the end of his article stating:

A second, rarely touched upon question is associated with the apparently limited amount of organic carbon that had been released from permafrost terrain in previous periods of climatic warming such as e.g. the Medieval Warm Period or during the Holocene Climatic Optimum. There appear to be no significant CH4-excursions in ice core records of Antarctica or Greenland during these time periods which otherwise might serve as evidence for a massive release of methane into the atmosphere from degrading permafrost terrains.

In other words, the ice cores that have long been relied upon to show the chemical fluctuations in the atmosphere over many tens of thousands of years into the past—the ones that are used to related changes in atmospheric greenhouse gases such as carbon dioxide and methane to changes in global temperatures—fail to capture a large methane release during previous warm periods during the Holocene. This finding suggests that warmer temperatures in the Arctic—recall that Arctic temperatures were as warm as or warmer than present for several thousand years during the Climatic Optimum lasting from approximately 9,000 to 4,000 years ago—did not prompt a massive release of methane from permafrost melting.

The recent paper by Schaefer and colleagues in Science, also reported lack of evidence supporting the “catastrophic methane emissions from melting permafrost” scenario:

[O]ur δ¹³CH₄ record support neither catastrophic nor gradual clathrate emissions at the YD-PB [roughly 12.2 to 11.2 thousand years ago] transition." And this transition period has been estimated to have undergone perhaps as large as 28˚C (!) changes in winter temperatures or about 16˚C in annual-mean temperatures by Broecker in a 2006 paper in Global and Planetary Change. Such a large change in temperatures around the Greenland and Arctic region will not likely to be soon surpassed under any future man-made emission scenarios.

In fact, there is no evidence in the atmospheric record of methane concentrations to indicate that the current warm-up is causing a significant methane release from melting permafrost. In fact, the build-up of methane in the atmosphere has been dramatically slowing since the early 1980s, and is now quite close to zero on a year-over-year basis. This behavior of methane is documented (among other places) in a recent paper by Khalil and colleagues from Oregon Graduate Institute entitled “Atmospheric Methane: Trends and Cycles of Sources and Sinks” appearing in the journal Environmental Science and Technology.

Khalil et al. start their article noting “Methane concentrations in the atmosphere have more than doubled over the last century, raising concerns that it is contributing to global warming and will continue to do so in the future,” but then continue “Although these past increases were alarmingly rapid, subsequent measurements showed a persistent slowdown in the trends to nearly zero at present.”

They continue:

It is apparent that there are ups and downs, but these are superimposed on a systematically declining rate of accumulation. The slowdown of methane trends has been known and discussed for a long time; however, it is particularly noteworthy that the decrease of the methane trend is not a new phenomenon, but rather it has occurred from the time that systematic measurements were first taken. Most probably it started even before then. Since fluctuations are superimposed on a generally decreasing trend, there have been years in recent times when methane has not increased at all or has even fallen slightly relative to the previous year. This has attracted more interest than in the past when there were similar short-term down turns but on the whole methane still increased over previous years. The recent incursions of the trend into negative territory are therefore part of a much longer term process.

The annual trend in atmospheric methane concentration as compiled by Khlail et al. (2007). The trend has been declining since the early 1980s and currently approaches zero.

Khalil and colleagues summarize their findings thus:

The present data set spans more than two decades. It shows that both methane emissions and its lifetime may have been constant over this period. To quantitatively explain the decreasing trends of methane it is not necessary to look for decreasing sources or increasing OH [hydroxyl radical]. During the time of the measurements if either has changed the other must also have changed by a proportionate amount to account for the observed trends. Moreover, while such circumstances may have occurred, if the sources have increased in the past they would have no environmental consequences such as increased global warming, because the extra amounts put into the atmosphere would be the same amounts that would have to be taken out by the increased OH to be consistent with the observed concentrations of methane during the last two decades. The concentrations behave exactly as if the sources and sinks had been constant. A confirming aspect of this apparent constancy of sources and sinks is that the trend has been decreasing for the last two decades until the present when it has reached near zero, thus attracting renewed attention. The major agricultural sources such as rice agriculture and cattle have little or no potential for large increases in the future and have already shown reduction in emissions from some regions. Seeing that the total source has remained constant for at least the last two decades, it is questionable whether human activities can cause methane concentrations to increase greatly in the future. This prediction is within the lower range of the IPCC SRES scenarios. [emphasis added]

The great majority of projections of future methane concentrations as put forth by the Intergovernmental Panel on Climate Change (IPCC) likely err on the high side as the build-up rate of atmospheric methane concentration has slowed for the past 30 years and now is near zero.

Secondly, there is absolutely no indication at all that global methane emissions have increased (from sources such as permafrost melting) during the past 30 years despite the global warming that has taken place. This finding, coupled with the results from Delisle that a massive methane release from future permafrost melting is not anticipated, is strong indication that alarmist scare stories about Arctic warming leading to a runaway greenhouse effect are simply ungrounded in the best available science.

References:

Broecker, W. S., 2006. Abrupt climate change revisited. Global and Planetary Change, 54, 211-215.

Delisle, G. 2007. Near-surface permafrost degradation: How severe during the 21st century? Geophysical Research Letters, 34, L09503, doi:10.1029/2007GL029323.

Khalil, M.A.K., C.L. Butenhoff, and R.A. Rasmussen, 2007. Atmospheric Methane: Trends and Cycles of Sources and Sinks. Environmental Science and Technology, available on-line (10.1021/es061791t).

Schaefer, H., et al., 2006. Ice record of δ¹³C for atmospheric CH₄ across the younger-dryas-preboreal transition. Science, 313, 1109-1112.