Methane bubbles surfaced beside Smith Lake as ecologist Ted Schuur walked along its edge in Alaska, where thawing permafrost is adding greenhouse gases to pollution from coal, oil and natural gas. Two studies project that permafrost gases could add about a quarter degree Celsius of warming by the end of the century; other estimates in the research put the potential contribution at nearly half a degree.
The ground is shifting beneath homes, roads and pipelines that communities and industry have long relied on. In Kotzebue, Alaska, thawing permafrost warped a road. In Newtok, coastal permafrost was melting. Photographers dated the images documenting those conditions Sept. 26, 2025, and Aug. 16, 2024, respectively. People treated the frozen ground as a stable foundation. It isn’t behaving like one now.
The carbon beneath the ground
Permafrost is ground that remains frozen below 32 degrees Fahrenheit, or zero degrees Celsius, for at least two years; in many places, it has stayed frozen for centuries or millennia. It holds decomposing plants and animals before they release greenhouse gases. As the Arctic warms four times faster than the rest of the globe, that stored material is thawing and decaying into 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 the process one of climate change’s “scary tipping points” and said, “Essentially every year is setting a permafrost record.” Permafrost contains three times as much carbon as is currently in the atmosphere, he said.
For thousands of years, the Arctic acted as a carbon sink: plants drew heat-trapping gas from the air and stored it in frozen ground. A few years ago, warming shifted that balance, and thawing ground began 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.”
A September study co-authored by Sue Natali of the Woodwell Climate Research Center found that permafrost thaw and other warming-induced emissions from fires and changes to wetlands and lakes are likely to increase warming by 20% by the end of the century. Natali and Hugelius said political and scientific estimates of future warming usually leave out the additional greenhouse gases from thawing permafrost. The United Nations estimate of 2.6 degrees Celsius above pre-industrial levels by the end of the century, without policy changes, excludes a few tenths of a degree from permafrost thaw.
A foundation giving way
Thaw doesn’t only release gases. It can destabilize the ground, causing formerly solid land to collapse and sink, Natali said. In Galbraith on Alaska’s North Slope, scientists recently saw a craterlike hole 10 feet deep. Ice melts to form these depressions, called slumps, and the land collapses, releasing methane. Using satellites, a Woodwell team has identified more than 40,000 slumps across the Arctic, according to scientist Kyle Arndt.
Flooding in Nepal killed more than 1,000 people this summer after part of a glacier collapsed following a heat wave that set records for the location and time of year, according to Berkeley Earth climate scientist Robert Rohde. Dmitry Streletskiy of George Washington University said weakened frozen ground was likely one of several factors in the disaster, though researchers haven’t determined the factors.
The problem is already here
University of Alaska Fairbanks geophysicist Vladimir Romanovsky said that when he began studying permafrost in the 1970s, “everybody believed permafrost was very stable. People thought it was forever.” He said that’s no longer the case. “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 preserves icy walls containing bison and mammoth bones. Workers artificially cool the tunnel, which they use for training. Its sewage-like odor comes from the source of Arctic methane. “Every time I go there, I’m reminded of the magnitude of the problem. You smell it. You see it. You feel it all around you,” Natali said. “This isn’t a problem of 100 years from now. This is a problem of right now.”