Methane gas can dramatically change the global climate

There are large uncertainties in the $60tn figure

Methane gas is one of the wildest of wild cards in the game of trying to assess future climate change. But among the many uncertainties, scientists know two things for sure: there is a vast amount of methane stored in the Arctic region, and if it were to be suddenly released into the atmosphere, it could dramatically change the global climate.

The latest study, it has to be said, is only the first, tentative stab at trying to assess the economic impacts of a sudden methane release from the Arctic. Unlike the usual peer-reviewed research papers in Nature, this one was clearly published under the rubric of “comment”.

The three researchers – an economist, a social scientist and an Arctic ice specialist – have broken new ground by tackling the difficult issue of assessing the economic costs of a large-scale escape of methane, which as a greenhouse gas is 20 times more potent than carbon dioxide over a 100-year period.

They used an economic computer model called PAGE09 which was also used by the Stern Review into climate change costs and the US Environmental Protection Agency. They estimated, on average, it would cost a staggering $60 trillion (£40tn) if just one of the known Arctic methane reserves were to be suddenly released as a result of melting permafrost.

Some will no doubt argue that these kinds of computer models are not to be trusted, and there are many assumptions and uncertainties lying behind this kind of work. Nevertheless, the researchers believe this is a useful exercise in balance given the optimism over the supposed economic benefits of Arctic oil and gas exploration, to say nothing of the shipping bonanza offered by an ice-free Northern Sea Route between Japan, China and Europe.

There are large uncertainties even in this $60tn figure. There is a 5 per chance that the costs could be as little as $10tn and a 5 per cent chance of them being as high as $220tn. But 80 per cent of this extra financial burden is likely to fall on the poorer nations of Africa, Asia and South America, which will suffer most as methane magnifies the risk of flooding to low-lying areas, extreme heat stress, drought and storms.

“What the model does is allow us to work out how much extra temperature rise there is and we find in average terms it brings forward the date at which the 2C temperature rise is exceeded by somewhere between 15 and 35 years,” explained Chris Hope, an economist at Cambridge University.

“As the temperature and sea levels rise, we can the go on to estimate the extra impacts in the regions around the world and in different economic sectors,” Dr Hope said.

“Of course the answer is uncertain, as everything about the climate is uncertain, but we can run the model many thousands of times to try to take account of this uncertainty,” he said.