FAIRBANKS, Alaska — Methane trapped for millennia in Arctic permafrost is increasingly escaping into the atmosphere as the frozen ground thaws, accelerating global warming, scientists warn. Researchers say the Arctic is warming about four times faster than the rest of the planet, causing once-stable frozen soils to release potent heat-trapping gases such as methane and carbon dioxide.

Ted Schuur, an ecologist at Northern Arizona University, observed methane bubbles surfacing from thawing muck along Smith Lake in Alaska. He described the phenomenon as a “scary tipping point,” noting that permafrost contains about three times more carbon than currently present in the Earth's atmosphere. As the permafrost thaws, the organic matter previously preserved in the frozen soil decomposes into greenhouse gases, which then add to emissions from fossil fuel combustion.

Permafrost is soil that remains frozen for at least two consecutive years and often for centuries or longer. It is found across the Arctic, including Alaska, Canada, Siberia, as well as Antarctica and high mountainous regions elsewhere. This frozen ground historically acted as a carbon sink by trapping dead plants and animals, preventing their decay into greenhouse gases. It also provides a stable foundation for communities and industries in cold regions.

However, rising temperatures are undermining these functions. Two recent studies project that by the end of the 21st century, greenhouse gas emissions from thawing permafrost could contribute approximately 0.25 degrees Celsius (0.45 degrees Fahrenheit) of additional global warming, on top of emissions from human activities. Scientists note this level of warming would be comparable to the overall emissions impact of an industrialized region like the United States or the entire European Union.

Gustaf Hugelius, a Stockholm University permafrost expert, described the permafrost as a “sleeping giant” that has maintained Earth’s carbon balance for thousands of years. Historically, the cooler Arctic climate allowed plants to absorb substantial amounts of atmospheric carbon, storing it safely in frozen soils. But warming has reversed this balance, turning the Arctic into a net source of greenhouse gases.

Columbia University ecologist Duncan Menge emphasized that the Arctic now contributes to climate change rather than mitigating it. Alongside permafrost thaw, other climate-driven changes such as increased wildfires and alterations in wetlands and lakes are projected to raise global warming by roughly 20 percent by century's end, according to a recent study led by Arctic ecologist Sue Natali of the Woodwell Climate Research Center.

These findings highlight the urgent need to understand and address feedback loops from permafrost thaw, which could complicate global efforts to limit climate change. Scientists caution that ongoing emissions from thawing permafrost may set in motion long-term changes that persist even if human greenhouse gas emissions are reduced.