“Lately, as summers have lengthened and winters have warmed, this seasonal transformation has lost its symmetry. What biologists call the permafrost’s “active layer”—the part of the dirt where microbes and other forms of life can live—now reaches farther underground, and further north, than it has for tens of thousands of years.
The newly active permafrost is packed with old stuff: dead plants, dead animals, mosses buried and reburied by dust and snow. This matter, long protected from decomposition by the cold, is finally rotting, and releasing gases into the atmosphere that could quicken the rate of global warming.
This matter is also full of pathogens: bacteria and viruses long immobilized by the frost. Many of these pathogens may be able to survive a gentle thaw—and if they do, researchers warn, they could reinfect humanity.
Climate change, in other words, could awaken Earth’s forgotten pathogens. It is one of the most bizarre symptoms of global warming. And it has already begun to happen.”