“The problem is, you can’t just turn off, let alone reverse, permafrost thaw,” one scientist said. “It won’t be possible to refreeze the ground and have it go back to how it was.” Photographs by Alexander Gronsky for The New Yorker

Joshua Yaffa reminds me, vividly, that my work in Yakutia 16 years ago was an exercise in futility:

The Great Siberian Thaw

Permafrost contains microbes, mammoths, and twice as much carbon as Earth’s atmosphere. What happens when it starts to melt?

Flying over Yakutia, in northeastern Russia, I watched the dark shades of the boreal forest blend with patches of soft, lightly colored grass. I was strapped to a hard metal seat inside the cabin of an Antonov-2, a single-­engine biplane, known in the Soviet era as a kukuruznik, or corn-crop duster. The plane rumbled upward, climbing above a horizon of larch and pine, and lakes the color of mud. It was impossible to tell through the Antonov’s dusty porthole, but below me the ground was breathing, or, rather, exhaling.

Three million years ago, as continent-­size glaciers pulsed down from the poles, temperatures in Siberia plunged to minus eighty degrees Fahrenheit and vast stretches of soil froze underground. As the planet cycled between glacial and interglacial periods, much of that frozen ground thawed, only to freeze again, dozens of times. Around eleven and a half millennia ago, the last ice age gave way to the current interglacial period, and temperatures began to rise. The soil that remained frozen year-round came to be known as permafrost. It now lies beneath nine million square miles of Earth’s surface, a quarter of the landmass of the Northern Hemisphere. Russia has the world’s largest share: two-thirds of the country’s territory sits on permafrost.

In Yakutia, where the permafrost can be nearly a mile deep, annual temperatures have risen by more than two degrees Celsius since the Industrial Revolution, twice the global average. As the air gets hotter, so does the soil. Deforestation and wildfire—both acute problems in Yakutia—remove the protective top layer of vegetation and raise temperatures underground even more.

Over thousands of years, the frozen earth swallowed up all manner of organic material, from tree stumps to woolly mammoths. As the permafrost thaws, microbes in the soil awaken and begin to feast on the defrosting biomass. It’s a funky, organic process, akin to unplugging your freezer and leaving the door open, only to return a day later to see that the chicken breasts in the back have begun to rot. In the case of permafrost, this microbial digestion releases a constant belch of carbon dioxide and methane. Scientific models suggest that the permafrost contains one and a half trillion tons of carbon, twice as much as is currently held in Earth’s atmosphere.

Trofim Maximov, a scientist who studies permafrost’s contribution to climate change, was seated next to me in the Antonov, shouting directions to the pilot in the cockpit. Once a month, Maximov charters the plane in order to measure the concentration of greenhouse gases in the atmosphere above Yakutia. He described the thawing permafrost as a kind of feedback loop: the release of greenhouse gases causes warmer temperatures, which, in turn, melt the permafrost further. “It’s a natural process,” he told me. “Which means that, unlike purely anthropogenic processes”—say, emissions from factories or automobiles—“once it starts, you can’t really stop it.”

A hose attached to the plane’s wing sucked air into a dozen glass cylinders arrayed on the floor of the cabin. By comparing the greenhouse-gas numbers over time, and at various altitudes, Maximov can estimate how permafrost is both affected by a warmer climate and contributing to it. When he started taking airborne measurements, half a decade ago, he found that the concentration of carbon dioxide in the air above Yakutia was increasing at double the rate of historical averages. Methane has a shorter life in the atmosphere than carbon dioxide, but it is more than twenty-­five times as effective at trapping heat. According to Maximov’s data, methane is also being released at an accelerated rate: it is now accumulating fifty per cent faster than it was a generation ago.

At the moment, though, I was mainly concerned with the stomach-turning lurches the plane was making as it descended in a tight spiral. We had dropped to a few hundred feet above the ground so that Maximov’s colleague, a thirty-three-year-old researcher named Roman Petrov, could take the final sample, a low-altitude carbon snapshot. The plane shook like a souped-up go-kart. Petrov held his stomach and buried his face in a plastic bag. Then I did the same. When we finally landed, on a grass-covered airstrip, I staggered out of the cabin, still queasy. Maximov poured some Cognac into a plastic cup. A long sip later, I found that the spinning in my head had slowed, and the ground under me again took on the feeling of reassuring firmness—even though, as I knew, what seemed like terra firma was closer to a big squishy piece of rotting chicken.

Throughout the seventeenth and eighteenth centuries, as the Russian Empire expanded eastward, reports filtered back to the capital of a “firm body of ice” in the ground, in the words of one explorer, that “was never heard of before.” In Yakutsk, the capital of Yakutia, early settlers struggled to grow crops and find sources of fresh groundwater. In the summer of 1827, a merchant named Fedor Shergin, whom the tsar had dispatched to Yakutia as a representative of the Russian-­American Company, tried to dig a well. Shergin’s team of laborers spent the next decade chiselling a shaft, reaching three hundred feet down, only to find yet more frozen earth. Finally, in 1844, Alexander von Middendorff, a prominent scientist and explorer, made his way from St. Petersburg to Yakutsk and estimated, correctly, that the soil under the shaft was frozen to a depth of at least six hundred feet. His findings jolted the Russian scientific academy, and eventually reached the salons of Europe…

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