The most recent IPCC assessment projects a loss of near-surface permafrost of between 37 and 81 percent by 2100, though most scientists still believe that carbon will be released slowly, and mostly as less-terrifying carbon dioxide. But as far back as 2011, NOAA and the National Snow and Ice Data Center predicted that thawing permafrost would flip the whole region from being what is called a carbon sink, which absorbs atmospheric carbon, to a carbon source, which releases carbon, as quickly as the 2020s. By 2100, the same study said, the Arctic could release a hundred billion tons of carbon.
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