This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: As Ted Schuur stepped along the edges of Smith Lake, a bubble surfaced from the muck underfoot. They're bubbles of methane, a potent heat-trapping gas made from decomposing plants and animals that had once been stuck in Alaska's frigid permafrost.
But that frozen ground is thawing because the Arctic is warming four times faster than the rest of the globe. For thousands of years that frozen ground stored dead plants and animals, but the accelerating thaw is allowing them to decay 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," said Schuur, an ecologist at Northern Arizona University, calling it one of climate change's scary tipping points.
"Essentially every year is setting a permafrost record." There's three times as much carbon still frozen in permafrost than what's now in the air, but all over the Arctic those heat-trapping gases are escaping into the atmosphere. Their release adds to what's already in the air from humanity's burning coal, oil and natural gas, changing the delicate balance of how a warming world deals with the buildup of heat-trapping carbon, Schuur said. Permafrost is ground that stays frozen—below 32 degrees Fahrenheit (zero degrees Celsius)—for at least two years and often for centuries and even millennia.
That frozen ground—found in Alaska, Canada, Siberia, Antarctica and high mountain elevations elsewhere—has special advantages, trapping decaying matter, keeping it from turning into greenhouse gases and just being firm enough for communities and industries to build their lives upon. Two different studies project that by the end of this century, those previously trapped gases in permafrost will add nearly half a degree of warming (about a quarter degree Celsius) in addition to warming from the burning of fossil fuels. Over that time period, that'll warm the Earth about as much as a major industrialized country like the United States or the whole of Europe, scientists said.
"The permafrost system is really like a sleeping giant," said Gustaf Hugelius, a permafrost expert at Stockholm University. For thousands of years, when the climate was somewhat stable, the Arctic helped Earth's delicate carbon cycle by acting as a sink. That means plants in the cold areas used to pull some heat-trapping gas out of the air and capture it in the frozen ground, with the Arctic essentially withdrawing more carbon from the air than it added, benefiting the entire globe.
A few years ago, warming caused that balance to shift so that once-frozen ground is venting more heat-trapping gases than it takes in. Instead of reducing climate change, the Arctic is now adding to the problem, said Columbia University ecologist Duncan Menge. Permafrost thaw, along with 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, according to a September study co-authored by Arctic ecologist Sue Natali of the Woodwell Climate Research Center.
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