A hill of permafrost “slumping” on Aug. 10, 2009 in the Northwest Territories, Canada. (Rick Bowmer/AP)

The Arctic is one of the most vulnerable parts of the world when it comes to climate change, and has the potential to contribute some costly climate-related effects, such as sea-level rise from melting glaciers. But one of the biggest emerging talking points in conversations about climate change in the Arctic involves something else — permafrost.

This frozen soil typically contains large amounts of carbon-containing organic matter. That’s fine as long as the soil stays frozen — but as the Arctic continues to heat up year after year, more and more permafrost is starting to thaw, unleashing its stored carbon into the atmosphere in the process in the form of both methane and carbon dioxide, mostly the latter. Altogether, scientists estimate that Arctic permafrost could contain 1,700 gigatons (which is equal to 1.7 trillion tons) of carbon.

The release of some of this carbon, even gradually, could have dramatic consequences for the climate, leading to an acceleration in global climate change, more warming in the Arctic, and more thawing, which would consequently cause more carbon to be released in a kind of vicious cycle. But what haven’t been closely examined, until now, are the economic consequences of this thawing permafrost.

As it turns out, they could be very large. Chris Hope, an expert in policy modeling at the University of Cambridge, and Kevin Schaefer, a research scientist at the National Snow and Ice Data Center, have concluded that carbon emissions from thawing permafrost could cost the world trillions of dollars over the next 200 years.

In a study published Monday in the journal Nature Climate Change, the researchers used two models — one that estimates emissions from thawing permafrost and one that calculates the resulting temperature increases and global climate-related impacts — to evaluate the global economic impact of permafrost emissions up through the year 2200. They suggest that carbon emissions from thawing permafrost could cause climate effects which will cost the world approximately $43 trillion over the next 200 years. This would increase the total economic impact of climate change, which is currently estimated to come to about $326 trillion, by 13 percent.

“There is almost nothing in the literature on this,” said Hope, the lead author, in an e-mail to The Post. “We are the first to combine a physical model and an integrated assessment model in this way.”

When carrying out the modeling, the researchers assumed a climate scenario in which anthropogenic greenhouse gas emissions (that’s emissions caused by humans actions, like coal-burning) are allowed to continue until the year 2100, when their atmospheric concentration reaches 700 parts per million — a high emissions scenario. But after 2100, the researchers assumed there would be no more anthropogenic greenhouse gas emissions — an assumption they consider conservative.

As the planet heats up in this scenario, thawing permafrost in the Arctic releases both carbon dioxide and methane — enough to cause global temperatures to rise by between 0.11 and 0.25 degrees Celsius in 2100, on top of the warming that anthropogenic emissions would have already caused, according to the researchers’ calculations.

And even though Hope and Schaefer assumed that anthropogenic emissions would cease after 2100, warming is expected to continue for decades afterward. That means permafrost will continue to thaw up through 2200 and beyond, and will continue to add to rising temperatures throughout that time.

The extra warming is expected to cause a variety of serious consequences, including agricultural losses, an increased need for air conditioning, greater incidence of disease and detriments to natural ecosystems — all of which will cost the world money. Altogether, using their model, the researchers predict that the extra climate impacts from permafrost emissions could cost anywhere from $3 trillion to $166 trillion, with $43 trillion being the average.

It’s a big number no matter what — but the huge potential monetary range speaks to the many uncertainties still associated with the behavior of permafrost and our understanding of the planet’s reaction to greenhouse gas emissions. There are many factors that could change the amount of warming the planet will experience in the future and the consequences that will occur as a result. 

“The large range is just an honest reflection of the uncertainty that exists,” Hope said in his email. “We think it is important to model the full range of risks that we might face.”

The biggest uncertainty factor affecting the models, said senior author Schaefer, is a phenomenon known as the “transient climate response,” which refers to uncertainties in 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,” Schaefer said. “If it’s a smaller value, then the warming is less.” Accounting for these potential differences in the Earth’s future response to emissions is a big influence on the model, and could lead to greater or lesser climate consequences in the future, which will translate to higher or lower costs.

Continued collaboration between scientists and economists could narrow the range of potential impacts over time, Hope said, “but we have to make decisions while there is still considerable uncertainty, so modelling the full range of risks is the appropriate course to take.”

The most important of these decisions, Schaefer said, is to reduce anthropogenic emissions as quickly as possible. “There’s only one way to stop the thawing of permafrost, and that’s to stop climate change,” he said.

In fact, in their study the researchers also calculate the effects of aggressive emissions reduction efforts and find that it’s possible to scale back the economic impacts of thawing permafrost to a mean of about $6 trillion, rather than $43 trillion.

“The whole thing about reducing emissions is that it’s portrayed as environment versus jobs, the economy versus the climate, and it’s not that case at all,” Schaefer said. By investing in renewable energy and setting up the appropriate incentives for consumers to choose low-carbon options, he said, “We can grow the economy by harnessing the same market forces that caused the climate change problem in the first place.”

Also in Energy & Environment:

The world’s 3 trillion trees, mapped

Global warming ‘pause’ never happened, scientists say

Why storing solar energy and using it at night is closer than you think

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