Greenhouse gases released as global warming thaws permafrost in Arctic regions could increase the economic toll of climate change by trillions of dollars, scientists say.

The release of the carbon dioxide and methane normally trapped in the frozen ground could increase the economic damage from climate change by as much as $43 trillion by the end of the next century, a study by U.S. and British researchers predicts.

The researchers at the University of Colorado and the University of Cambridge have created the first models of the economic impact of melting Arctic permafrost and added that to the $326 trillion impact already predicted by other climate and economic modeling.

The researchers combined two models, one estimating total likely emissions of greenhouse gases from melting permafrost, the other calculating the temperature increases that would result in climate-related impacts worldwide, to create their prediction for 2200.

"There is almost nothing in the literature on this," says Chris Hope, a policy modeling expert at Cambridge.

"We are the first to combine a physical model and an integrated assessment model in this way," says Hope, lead author of the study appearing in the journal Nature Climate Change.

The researchers based their estimates on the assumption that anthropogenic greenhouse gas emissions resulting from human activities such as fossil fuel burning would continue until at least 2100.

By that year, release of methane and carbon dioxide from melting permafrost could push global temperatures up by between 0.11 and 0.25 degrees Celsius over what would already be present due to human-caused emissions, they predict.

By 2100, those human activities by themselves are expected to boost carbon dioxide levels by 75 percent over what they are today, they say.

The Arctic — where around 1,700 gigatons of carbon are trapped in permafrost — is warming at twice the rate of the global average, the researchers note, and if that rate continues, hundreds of billions of tons of greenhouse gases will be released as the permafrost thaws.

"These results show just how much we need urgent action to slow the melting of the permafrost in order to minimize the scale of the release of greenhouse gases," Hope says.

The researchers acknowledge that their models have a large uncertainty factor due to something known as the "transient climate response," a difficulty in gauging just how sensitive global temperatures are to atmospheric carbon dioxide concentrations.

"If you assume a bigger transient climate response, the model climate is warmer for the same amount of carbon dioxide input," says study senior author Kevin Schaefer at the National Snow and Ice Data Center at the University of Colorado. "If it's a smaller value, then the warming is less."

Still, says Hope, the study findings point to a clear need to reduce human-caused emission levels as much as possible and as soon as possible.

"There's only one way to stop the thawing of permafrost, and that's to stop climate change," he says.

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