Free The World in 2050: Four Forces Shaping Civilization's Northern Future by Laurence C. Smith

perhaps even offsetting the greenhouse effect thanks to faster-growing plants, thus storing more carbon even faster than before? Or will the microbes wake up and chow down, feasting on thousands of years of accumulated compost and farting voluminous quantities of methane and carbon dioxide back into the air? I’m not suggesting that sixteen hundred gigatons of deeply frozen soil carbon could all be returned to the atmosphere at once, but even 5% or 10% of it would be enormous.
    This possibility is another one of those climate genies that we are only just beginning to assess. Compared with the previous two, relatively little work has been done on it. Most permafrost research has traditionally focused on engineering, i.e., how to build structures without thawing the ground, thus slumping it and destroying what was built. Hardly anyone cared much about permafrost carbon until recently.
    We don’t know how quickly or deeply permafrost will thaw or how quickly and deeply the microbes will get to work. The microbes themselves generate heat, and we’re not sure how much this will further enhance the permafrost thawing process. The net outcome—net carbon storage versus net carbon release—hinges on a small difference between two far larger and opposed numbers (i.e., the rates of plant primary production versus microbial decomposition). Both numbers are difficult to measure and have large uncertainties associated with them.
    Much also depends on hydrology. The millions of lakes sprinkled across permafrost landscapes are themselves heavy greenhouse gas emitters and even bubble forth with pure methane, so their fate, too, is intimately tied to our climate future. Also, if thawed permafrost soils become dry and aerated (as might be expected if deep permafrost goes away), then microbes will release stored carbon in the form of carbon dioxide. If soils stay wet (as might be expected from climate model predictions of increased northern precipitation), then microbes will release it as methane, which is twenty-five times more potent a greenhouse gas than carbon dioxide. Given all these uncertainties, our current generation of computer models contain significant knowledge gaps. I’d wager we have twenty years’ work ahead of us before a solid scientific consensus can be reached on what will happen to this big mess of carbon as it defrosts. 509
    We do know this very same landscape switched on to become a major source of greenhouse gas once before—at the end of the last ice age, when northern peatlands first began to form. About 11,700 years ago, as temperatures rose at the end of the Younger Dryas cold shudder, a threshold was crossed, plants began growing, and peatlands sprang up all around the Arctic, pumping out enormous volumes of methane. 510 We also know, from a single study in Sweden, that rising air temperatures penetrate permafrost soils more quickly and deeply than we thought. From two other studies in West Siberia, we know that although thawed soils ooze up to six times more dissolved carbon into rivers and lakes than frozen soils, they also store carbon faster—or at least they did for the past 2,000 years. This is at odds with a different study in Alaska, which suggests that faster-growing plants will not be able to outpace the faster-decomposing microbes once the permafrost disappears. Finally, we know some simple math: If even 2% of this frozen carbon stock somehow returns to the atmosphere between now and 2050, it will cancel out the Kyoto Protocol Annex 1 target reductions more than four times over. Like the West Antarctic Ice Sheet, this is one genie with global repercussions that we should all hope stays asleep.

CHAPTER 10
    The New North
    W ithin hours after the CCGS Amundsen docked at Churchill, my life had changed completely. After months of railroads through desolate boreal forest, long empty coastlines, and the cold salt air of Hudson Bay, I sank back into the smog-choked din of my sweating desert megacity. It