It’s easy to blow off global warming, especially when we hardly notice it. The most dramatic and rapid effects of climate change are felt more by polar bears than humans — far, far away from human inhabitation in the permanently frosted-over soils of the Arctic.
Way up north among Arctic foxes and penguins, temperatures have risen 0.6 degrees Celsius in the last 30 years, which is twice as fast as the global average. We’ve all heard the stories of polar bear habitat demise, but a quieter, less well understood story is the effect that thawing has on greenhouse gas release.
Over thousands of years, countless plants and animals have died in Arctic regions, and their bodies have accumulated in perennially frozen soils, stored as carbon. Just like putting food in a freezer, freezing organic matter (once-living dead things) puts a stop to decomposition, storing the carbon in “carbon pools”.
Leave food out in the warmth, though, and it will start to decompose, releasing small amounts of carbon dioxide and methane into the atmosphere. The same goes for carbon stores in permafrost regions: once it’s warm enough, microbes go to work on the carbon and turn it into carbon dioxide and methane — greenhouse gases. The nasty twist is there is twice as much carbon stored in the Arctic as in the entire atmosphere. To top it off, the Arctic is warming faster than other parts of the Earth, but how fast are the greenhouse gases being released, and what are the effects?
Predicting the effects permafrost thaw will have on the Earth is difficult, simply because we don’t have enough data. Recently, Nature compiled research on permafrost carbon dynamics from the last few years. A major takeaway is how much we don’t yet understand.
Carbon stores in the top three metres of Arctic soil have been relatively well sampled; the result is an estimate of 1035 billion tons of carbon compared to 2000 billion tons of carbon in the rest of the world’s surface soil. Sampling below three metres is more difficult, and samples are scarce. Even with the newest research the estimate is vague, wavering between 210 and 456 billion tons of carbon. And reaching carbon stores far beneath the Arctic Ocean is even harder. To complicate undersea carbon dynamics, microbes have been decomposing unknown quantities of carbon and transforming it into greenhouse gases at a rate we also don’t yet know.
Permafrost carbon emissions will warm the earth steadily over decades to centuries: faster than they would without the help of human activities, but slower than some of the most drastic estimates. For the time being, there’s no need to panic; the Earth will remain intact for a few more years.