Friday, October 24, 2014

Methane Hot Spots and Global Warming

(contributed by Emma Seddon)

Recent reports by the Intergovernmental Panel on Climate Change (IPCC) have concentrated more on the effects of rising greenhouse gases and how we can mitigate their impact and adapt to changing conditions rather than on the problem itself, the reasons for these increases. It acknowledges the large contribution to global mean temperatures made by methane, which has a radiative flux (RF) factor 34 times greater than carbon dioxide, i.e. as a greenhouse gas it is extremely efficient at trapping heat within the atmosphere. The conclusion has to be that although carbon dioxide persists in the atmosphere for thousands of years compared to methane’s average lifetime of 12 years, if you take into account methane’s global warming potential of around 25 times that of carbon dioxide over the timescale of a century, and 72 times its potency over 20 years, tackling the methane problem has to be a good short-term aim.

Emission hot spots

Although most of the methane present in the atmosphere is due to natural causes such as emissions from wetlands and ruminative animals, human activity has played a large part in the increased levels seen during recent decades. There is no easy solution to the problem of trying to reduce these emissions. On the one hand, much of the methane we release into the atmosphere comes from our vast herds of livestock, and without a mass movement towards vegetarianism there is no real likelihood that these can be reduced in the near future.

On the other hand, various “hot spots” of methane emissions have been observed, and it is not always clear why these are occurring and why there has been a dramatic rise in methane levels during the past year following a general slow reduction of levels over the past 20 years. These emissions are made up of a mix of natural sources and the results of human activity, the most visible being the natural release of methane cause by the warming arctic waters off the Siberian coast thawing methane hydrates on the ocean floor, and the leakages from natural gas production, particular as a result of the booming fracking industry. In Utah alone, it has been estimated that up to 12% of natural gas produced by fracking is released into the atmosphere, although this is probably a worst-case scenario: other fracking sites such as those in Colorado are somewhat cleaner, with only 4% leakage measured in one Denver field. This in itself is no small figure, which has caused concern amongst the industry’s critics. A solution to the spiraling level of emissions caused by human activity is already present in the drive towards a greater reliance on eco-friendly methods of energy production, but this can only happen if there is strong political backing that provides the energy industry with incentives for change.

One methane hot spot discovered in the US Southwest that was so large it was initially put down as an erroneous instrument reading. Another even larger hot spot has been detected by satellite covering an area of about 2,500 square miles where the borders of Colorado, Arizona, Utah and New Mexico meet, the Four Corners Region, which has produced the largest concentration of natural methane emissions ever discovered in the US. This is over three times the volume for any other emission hot spot. Several theories were put forward to explain the anomaly, one of which attempted to blame methane produced by coal mining and the release of natural subterranean pockets of gas. However, the Four Corners Region is close to the San Juan Basin, which one of the areas of the country with the most intensive fracking activity and which still holds huge quantities of methane despite having been the site of oil and gas extraction by drilling since the 1920s.

If fracking is to blame, other major fracking sites such as Jonah Field and Powder River Basin in Wyoming, and Piceance Basin and Weld County in Colorado, should show the same levels of methane emissions. This is not the case. The picture is further confused: Weld County also has a high concentration of cattle feedlots, which are known to produce high levels of methane, yet in an apparent contradiction to this, the largest beef producer in California at Harris Ranch is also one of the largest hot spots. The answer appears to be both good and bad. It’s most probable that poor management of the various processes is to blame, producing leaks that are avoidable. We should be able to remedy the problem, but the continued high levels of methane being released into the atmosphere from the collective fossil fuel industries suggests that this may not happen very soon.

The Siberia leakage

The undersea leakage of methane in the East Siberian Sea was originally observed by a team of Russian and Swedish scientists as small columns of bubbles rising to the surface; these have recently been seen to have grown considerably, with hundreds of them in one small area described as “powerful and impressive seeping structures more than 1,000 meters in diameter.” The suggestion was that there were probably many thousands of these all around the Siberian coast.

On August 12, 2014, peak methane levels of 2441 ppb were recorded in the area at 19,820 ft, and these eruptions pushed the mean global methane levels up to 1832 ppb. One member of the observation team, Örjan Gustafsson, from the Department of Geological Sciences at Stockholm University, described methane levels in the seawater as being ten times the background level. The most reasonable current hypothesis is based around observation of the changing Gulf Stream in recent years: a tongue of warm Atlantic water at a core depth of between 200-600 meters has moved north and east along the Siberian continental shelf, destabilizing the methane hydrates along the upper edge of the submerged slope of the shelf and producing the high levels of methane released into the sea.

Negative arctic oscillation

These increased natural sources of methane pose a more difficult problem than that produced by fracking and other industrial processes, although they are undoubtedly caused, at least in part, by the warming seas and atmosphere, which is affected by the entire range of human activity that produces greenhouse gases. For many years, the arctic has borne the brunt of these changes. Arctic weather systems are becoming erratic, and this has produced some unusual effects known as negative arctic oscillation, or the polar vortex, the reversal of the usual temperature gradients towards the pole produced by the changing path of the jetstream—for example, last year Lake Erie froze before Hudson Bay, which is about 500 miles farther north, and Greenland’s ice melt season was extended by fifty days. The Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the University of Washington’s Polar Science Center has observed that the arctic ice sheets are thinning as well as receding, and this has been confirmed by the European Space Agency’s CryoSat-2 probe. The result is a reduction in arctic ice volume, which is now only one fifth the minimum recorded in 1980.



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