Arctic melt: Increasing temperatures in the Arctic region are reducing sea ice cover and increasing the possibility of methane leaching from the sea bed. Scientists say that the release of large amounts of methane from thawing permafrost in the Arctic could have huge economic impacts for the world. The researchers estimate that the climate effects of the release of this gas could cost $60 trillion (£39 trillion), roughly the size of the global economy in 2012. The impacts are most likely to be felt in developing countries they say. Scientists have had concerns about the impact of rising temperatures on permafrost for many years. Large amounts of methane are concentrated in the frozen Arctic tundra but are also found as semi-solid gas hydrates under the sea. Price of gas Previous work has shown that the diminishing ice cover in the East Siberian sea is allowing the waters to warm and the methane to leach out. Scientists have found plumes of the gas up to a kilometre in diameter rising from these waters. In this study, the researchers have attempted to put an economic price on the climate damage that these emissions of methane could cause. Methane is a powerful greenhouse gas, even though it lasts less than a decade in the atmosphere.

Scientists have identified thousands of sites in the Arctic where methane that has been stored for many millennia is bubbling into the atmosphere. The methane has been trapped by ice, but is able to escape as the ice melts. Writing in the journal Nature Geoscience, the researchers say this ancient gas could have a significant impact on climate change. Methane is the second most important greenhouse gas after CO2 and levels are rising after a few years of stability. There are many sources of the gas around the world, some natural and some man-made, such as landfill waste disposal sites and farm animals. Tracking methane to these various sources is not easy. But the researchers on the new Arctic project, led by Katey Walter Anthony from the University of Alaska at Fairbanks (UAF), were able to identify long-stored gas by the ratio of different isotopes of carbon in the methane molecules. Using aerial and ground-based surveys, the team identified about 150,000 methane seeps in Alaska and Greenland in lakes along the margins of ice cover. Local sampling showed that some of these are releasing the ancient methane, perhaps from natural gas or coal deposits underneath the lakes, whereas others are emitting much younger gas, presumably formed through decay of plant material in the lakes. "We observed most of these cryosphere-cap seeps in lakes along the boundaries of permafrost thaw and in moraines and fjords of retreating glaciers," they write, emphasising the point that warming in the Arctic is releasing this long-stored carbon.