Global warming will defrost much more permafrost than we thought, a new study finds. Every 1°C (1.8°F) of additional warming would thaw one-quarter of the earth’s frozen tundra area — releasing staggering amounts of heat-trapping greenhouse gases (GHGs).
Those GHGs would in turn warm the planet more, melting more permafrost, releasing more GHGs, and so on. This is perhaps the most dangerous amplifying carbon-cycle feedback humanity faces — considering permafrost contains twice as much carbon as the atmosphere does today.
That’s why it’s so vital the U.S. adheres to its commitments in the 2015 Paris climate agreement — a landmark accord in which the world unanimously committed to keep ratcheting down carbon pollution to ensure total warming stays “well below 2°C [3.6°F] above pre-industrial levels.” And that’s why President Donald Trump’s efforts to undermine the deal are so dangerous, since they may put the permafrost — and hence our livable climate — across a point of no return.
If we could limit total warming to the 1.5°C target identified in the Paris deal, that would save 800,000 square miles of permafrost compared to 2°C warming. But if the Trump administration succeeds in thwarting Paris, then we may lose more than half of the permafrost.
By way of background, the permafrost, or tundra, is soil that stays below freezing (0°C or 32°F) for at least two years. Normally, plants capture CO2 from the air during photosynthesis and slowly release that carbon back into the atmosphere after they die. But the Arctic acts like a very large carbon freezer — and the decomposition rate is very low. Or, rather, it was. We are leaving the freezer door wide open. The tundra is being transformed from a long-term carbon locker to a short-term carbon unlocker.
Significantly, while most of the carbon in a defrosting permafrost would probably be released as CO2, some would be released as methane, which which traps 86 times as much heat as CO2 over a 20-year period.
Yet one study found that the feedback from just the CO2 released by the thawing permafrost alone could add 1.5°F to total global warming by 2100, if we don’t sharply curtail carbon pollution as soon as possible. Worse, none of the models for the recent Fifth Assessment of the climate by the world’s top scientists incorporate loss of the permafrost in their warming assessments.
The bottom line of this new study was well summed up in the headline of its news release: “Huge permafrost thaw can be limited by ambitious climate targets.” And that means huge permafrost thaw can be caused by undermining those targets.