🔗 원문 전체 보기 → MIT Technology Review
요약
How much do you know about permafrost?
Maybe, like me, you’ve been aware that this layer of frozen soil is thawing, that it’s important in the global puzzle of climate change … and that’s about the extent of it.
The great news for both of us is that my colleague James Temple just published two in-depth stories about permafrost. His reporting took him to the boreal forests of Alaska, where he helicoptered into the wilderness to learn more about how this material could affect our climate both now and in the future.
I’d recommend you give both of James’s stories a read. There’s this feature about efforts to tackle the intensifying fires that are threatening permafrost, as well as this look at how researchers are trying to understand the complicated tangle of potential climate effects. Here are three things I took away.
Permafrost is a massive blind spot for climate change
Permafrost is the frozen layer of soil that’s under about 15% of land around the Northern Hemisphere. While technically material needs to be frozen for only two consecutive years to count as permafrost, most of our current permafrost formed during the last ice age.
That means there’s organic material that’s been frozen, and essentially locked away, for thousands of years. But as global temperatures tick up and this layer thaws, microbes are able to break down that organic matter, releasing carbon dioxide and methane—powerful greenhouse gases that drive climate change. Those emissions form a feedback loop, accelerating warming further.
The steady rise in global temperatures has already shrunk the footprint of the Arctic permafrost by about 12% since 1850, and the pace has been picking up in the last 50 years.
The wild thing is, only a minority of the models that have been used in UN climate reports actually take into account the gradual loss of permafrost. And none of them include the abrupt thaw and collapse that can happen after events like heat waves and fires (more on those fires in a moment). There are efforts to make sure future UN reports reflect the growing science, but for now, all this means that we’re probably underestimating how much and how fast the planet is going to warm.
Wildfires can speed up permafrost loss
Fire is a natural part of boreal forests’ life cycle, but they’re getting more intense because of climate change. And crucially, fires can accelerate the thawing of permafrost. By the end of the century, this effect could release the equivalent of 80 billion metric tons of carbon dioxide.
Today, the policy across remote parts of Canada and Alaska is generally to let wildfires burn as long as they’re not threatening human habitats. But some researchers say we should explore fighting these fires to save the carbon trapped in the forests and the permafrost beneath them.
Researchers at the Woodwell Climate Research Center are developing a map of burn risk and carbon vulnerability across Alaska, essentially highlighting areas where fires are most likely to spread and which areas are home to certain types of permafrost that would release the most emissions. (Yes, apparently there are different types of permafrost. Yedoma is a particularly deep, carbon-dense form from the late Pleistocene era.)
That’s all just the beginning—once we figure out potential targets, the question is what to do about it. Some suggest setting more prescribed fires, something Indigenous groups have done for thousands of years, partly to reduce the danger of massive blazes. Or resources could go to early detection and efforts to put out fires before they grow.
The carbon cycle of permafrost is incredibly complicated
There’s about 1.5 trillion tons of carbon locked away in permafrost, about twice the amount in the atmosphere. We know that permafrost thawing can release greenhouse-gas emissions and drive climate change. But there are complications.
One particularly big wrinkle: Other effects from permafrost thawing and fire recovery might counteract the carbon lost from those events. For example, as temperatures warm, plants can gradually move north and take hold where they couldn’t have before. Those plants soak up carbon from the atmosphere as they grow, at least partly locking away what was emitted.
Researchers are working to better understand this ecosystem. And the more we learn, the more complicated the picture looks. How much carbon is lost from permafrost, and how much a given area will recover its carbon, depend on a huge array of factors. How severe are the fires that have accelerated local thawing? What’s the local climate and environment? And what kind of permafrost is at stake?
The higher we push the planet’s temperature, the more we mess with complicated natural phenomena that we’re only beginning to understand.
This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.