A lot of Arctic infrastructure is threatened by rising temperatures

AQUARTER OF the northern hemisphere’s land is covered by permafrost, defined as ground that remains at or below 0°C for at least two years in succession. Most of this is above the Arctic Circle, a part of the world that is warming at a rate double the global average, with significant consequences for the rest of the planet. Arctic permafrost is thought to contain some 1.7trn tonnes of carbon, most of it in frozen organic matter. That is double the amount of the stuff currently residing in the atmosphere. Rising temperatures mean that much of this material may turn into carbon dioxide and methane as the ground thaws and micro-organisms get to work. That will drive further warming, causing a feedback loop of more melting and yet more greenhouse-gas emission.These risks are re-emphasised in a paper just published in . It warns that warming of the top three metres of permafrost alone could result in the release of 624m tonnes of carbon a year by 2100, a figure similar to the current emissions of Canada or Saudi Arabia. But a thawing Arctic poses other, more immediate, problems. Another paper published in the same journal highlights the threat posed to circumpolar infrastructure as the ground beneath it thaws.