Thawing Arctic permafrost could add about a quarter degree Celsius of warming by the end of the century, two studies project, adding to warming from fossil-fuel burning. A September study found that thaw and other warming-induced emissions from fires, wetlands and lakes are likely to increase warming by 20%. Scientists say many estimates of future warming don’t include those additional gases.
Carbon released from frozen ground
Permafrost holds three times as much carbon as the atmosphere currently contains, according to ecologist Ted Schuur of Northern Arizona University. When frozen ground thaws, plants and animals preserved for thousands of years decompose and release methane and carbon dioxide.
“Once you start leaking this carbon out, there’s so much in the ground that it’s not going to shut off,” Schuur said. He called it one of climate change’s “scary tipping points.” “Essentially every year is setting a permafrost record.”
Permafrost is ground that remains frozen below 32 degrees Fahrenheit, or zero degrees Celsius, for at least two years. It occurs in Alaska, Canada, Siberia, Antarctica and high mountain areas elsewhere. The Arctic is warming four times faster than the rest of the globe.
For thousands of years, Arctic plants pulled heat-trapping gas from the air and stored it in frozen ground, making the region a carbon sink. Warming shifted that balance “a few years ago,” and thawing ground started releasing more heat-trapping gases than it absorbs, said Duncan Menge, a Columbia University ecologist.
Gustaf Hugelius, a permafrost expert at Stockholm University, called the system “really like a sleeping giant.” Andrew Weaver, a University of Victoria climate scientist who first calculated the half-degree of expected permafrost warming in a 2012 study, said the amount may be small and not a “scenario of doom.” But it’s something “that we’re going to have to deal with” alongside other warming.
What climate estimates leave out
Without policy changes, the United Nations estimates the world will warm 2.6 degrees Celsius, or 4.7 degrees Fahrenheit, above pre-industrial levels by the end of the century. Sue Natali of the Woodwell Climate Research Center and Hugelius said political and scientific estimates usually leave out the extra greenhouse gases from thawing permafrost. They said the UN estimate excludes a few tenths of a degree from permafrost thaw.
Thaw can also weaken the ground. Formerly solid land may collapse and sink, Natali said. Using satellites, a Woodwell team identified more than 40,000 slumps across the Arctic, according to scientist Kyle Arndt. Ice melts, the land collapses, and methane escapes.
Ground instability in Arctic communities
Permafrost has supported homes, roads and pipelines in Alaska and other Arctic regions, but it’s becoming less reliable. In Galbraith on Alaska’s North Slope, scientists recently saw a craterlike hole 10 feet deep. A road warped in Kotzebue, Alaska, while coastal permafrost melted in Newtok, Alaska, according to photographs dated Sept. 26, 2025, and Aug. 16, 2024.
When University of Alaska Fairbanks geophysicist Vladimir Romanovsky began studying permafrost in the 1970s, “everybody believed permafrost was very stable. People thought it was forever.” That’s no longer the case, he said. “It took some thousands and tens of thousands of years to sequester this carbon into permafrost,” Romanovsky said. “You need a new ice age to put back this ice into the ground.”
A research tunnel drilled by the U.S. Army under a Fairbanks hill has icy walls that preserve bison and mammoth bones. The Army artificially cools the tunnel and uses it for training. Its sewage-like odor shows the source of Arctic methane, Natali said. “This isn’t a problem of 100 years from now. This is a problem of right now,” she said.