Just a week after researchers placed the cost of Arctic ice and permafrost melt as high as US$70 trillion, albeit over a span of nearly three centuries, a commentary in the journal Nature concludes that sudden permafrost collapse could double the warming from greenhouse gases released from northern tundra.
Last week, a study in the journal Nature Communications placed the cost of permafrost melt to the global economy in the trillions of dollars, noting that how many trillions will depend on whether countries adopt more ambitious controls on today’s greenhouse gas emissions, InsideClimate News reports . Now, a team of authors led by Merritt R. Turetsky, Canada Research Chair in the University of Guelph Department of Integrative Biology, is warning  that those long-feared Arctic feedbacks are already accelerating.
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“For tens of thousands of years, grasses, other plants, and dead animals have become frozen in the Arctic ground, building a carbon storeroom in the permafrost that’s waiting to be unleashed as that ground thaws,” InsideClimate explains. “It’s considered one of the big tipping points in climate change: as the permafrost thaws, the methane and CO2 it releases will trigger more global warming, which will trigger more thawing. The impacts aren’t constrained to the Arctic—the additional warming will also fuel sea level rise, extreme weather, drought, wildfires, and more.”
The economists and climate scientists behind the Nature Communications study put a price range on those impacts for the first time, based on a series of different outcomes for average global warming.
“Even if the goals of the Paris climate agreement are achieved—if the world keeps warming below 2.0°C from pre-industrial temperatures, or ideally below 1.5°C—the costs will be significant,” InsideClimate notes. “At 1.5°C of warming, thawing permafrost and loss of sea ice will have cost the global economy an estimated $24.8 trillion in today’s dollars by the year 2300. At 2.0°C, that climbs to $33.8 trillion.”
If all countries do is meet their promises under the 2015 Paris Agreement, the long-term price tag rises to $66.9 trillion.
“Those figures represent only a fraction of the total cost of climate change, somewhere between and 4% and 5%,” writes InsideClimate reporter Sabrina Shankman, citing lead author Dmitry Yumashev.” But they send an important message to policy-makers: namely, that the costs associated with keeping global warming to 1.5°C are less than the costs of the impacts associated with letting warming go to 2.0°C or higher.”
Turetsky and her colleagues note that permafrost soils hold twice as much carbon as the atmosphere, about 1,600 billion tonnes. And based on their field research, the main assumptions about how much of that carbon will be released, and at what pace, “could be a vast underestimate,” they conclude. Ultimately, “the impacts of thawing permafrost on Earth’s climate could be twice that expected from current models.”
“Current models of greenhouse gas release and climate assume that permafrost thaws gradually from the surface downwards. Deeper layers of organic matter are exposed over decades or even centuries, and some models are beginning to track these slow changes,” they write.
But the bigger problem is that permafrost physically holds the landscape together, in addition to sequestering carbon.
“Across the Arctic and boreal regions, permafrost is collapsing suddenly as pockets of ice within it melt,” they write. “Instead of a few centimetres of soil thawing each year, several metres of soil can become destabilized within days or weeks. The land can sink and be inundated by swelling lakes and wetlands.”
That dynamic has led to some dramatic discoveries. “Returning to field sites in Alaska, for example, we often find that lands that were forested a year ago are now covered with lakes,” Turetsky and her colleagues note. “Rivers that once ran clear are thick with sediment. Hillsides can liquefy, sometimes taking sensitive scientific equipment with them.”
In addition to the atmospheric impact, the sudden changes create severe problems for Arctic communities: “Roads buckle, houses become unstable. Access to traditional foods is changing, because it is becoming dangerous to travel across the land to hunt. Families cannot reach lines of game traps that have supported them for generations.”
The authors flag gaps in the available data that make their new perspective on permafrost a major research priority. “We can’t prevent abrupt thawing of permafrost,” they conclude. “But we can try to forecast where and when it is likely to happen, to enable decision-makers and communities to protect people and resources.” And “reducing global emissions might be the surest way to slow further release of permafrost carbon into the atmosphere. Let’s keep that carbon where it belongs—safely frozen in the stunning soils of the north.”