Heatwaves and wildfires are not just scorching forests, they add to tipping-point risks in the world’s vast permafrost regions, which contain three times more carbon than all living vegetation on Earth. This is a big concern for Gustaf Hugelius, a professor at the Bolin Center for Climate Research at Stockholm University, Sweden, and a leading authority on the risks of melting tundra and peatlands. In this Q&A, he explains why the world should pay attention. What is permafrost? Permafrost is ground frozen all year round. It is mainly found in Russian Siberia, Canada, Alaska and parts of Europe. The permafrost region is huge, covering 20 million square kilometres, five times the size of the EU. Why is permafrost a climate problem? Permafrost stores 1,500 gigatonnes of carbon, which is three times more than all the living vegetation on Earth, including all the trees in the Amazon. It’s a really huge amount, so even small changes in this system can cause big changes in the atmosphere. How can you reach a tipping point? Most of the time, permafrost has been frozen for thousands of years and contains many remains of ancient plants. This means that a lot of carbon is essentially locked in a freezer. But as humans warm the climate by burning gas, oil and coal, the permafrost begins to thaw and those plants become exposed to microbes, which eat the organic matter and then release carbon dioxide and methane. This enters the atmosphere and produces even more warming. This process can become self-reinforcing. MapCan’t it just refreeze later? No, because the thawing of the tundra creates a fundamentally different landscape. There is a lot of pure ice below the ground surface. When it melts, the water drains away and the surface collapses. This can create lakes, wetlands or river ravines. These new land formations, called thermokarsts, have a completely different hydrology that changes the thermal conductivity of the soil and snow conditions in winter. Once the permafrost threshold is passed and the ice disappears and the landscape changes, it will not appear again for hundreds of years. On a human time scale, those systems have effectively become a system that will continue to emit carbon for decades or centuries. Thermokarsts can turn the earth into a system that will continue to emit carbon for decades or centuries. Composite: Guardian Design/Supplied Could the entire system suddenly tilt? Not on a global level. The permafrost region is too large for the entire system to exceed a threshold at the same time, unless global warming reaches 6°C, which we hope will not happen now. But as the thaw progresses, there will be many local tipping points that will occur in succession. This has begun and some places have already passed irreversible tipping points. This increases pressure on the climate system and by the end of the century permafrost will become a major emitter in its own right. How much greenhouse gas could be released from permafrost this century? We could lose between 200 and 300 gigatonnes of CO2 equivalents if the world warms between 1.8°C and 3.6°C by the end of the century. This is many times more than the current EU emissions. Under even greater warming scenarios, the amount could be close to what the United States or even China are emitting today. Are there even more gloomy predictions than these? A couple of scientific papers predict very high methane flows, but those extreme scenarios are now considered unrealistic. The release of thawing permafrost is not expected to exceed all human emissions this century, but the general assumption is that this is a very serious problem, which is worsening the global challenge of reducing emissions. What difference does it make if permafrost releases methane instead of CO2? Methane is about 30 times more potent as a greenhouse gas, although only in the short term because it decomposes more quickly within 10 to 15 years. That makes it a strong and immediate concern for future generations. Carbon dioxide, by comparison, is less potent but persists much longer, making it a greater threat on a time scale of centuries. What factors determine whether permafrost releases methane or CO2? It depends on whether the thaw leads to a dry or humid environment. If the exposed landscape is dry (such as bare rock or soil), microbes will be able to oxidize carbon from previously frozen plants into CO2. But if the new landscape is a wetland or a lake, then the microbes will not have access to oxygen and will produce methane. One of the biggest research challenges we face is determining how much of the melting permafrost will become wetter and how much drier. How much permafrost loss has already been incorporated into the climate system? There is a decades-long lag between climate warming and permafrost thawing. This is because it is isolated in many parts of the tundra or boreal forest by vegetation and a thick layer of peat soil that delays the impact of snowmelt. The downside is that some areas of permafrost are already condemned, such as in northern Sweden and northern Finland. Even if we could stabilize the climate today, several million square kilometers of permafrost, mainly along the southern fringe of its range, are going to disappear because we passed its threshold a decade or more ago. On the plus side, if we could lower the temperature again, there are large areas where melting might never occur. The permafrost of Siberia and Canada may remain largely intact if the UN climate negotiations are successful. Researchers study the soil beneath grasslands. Composite: Guardian Design/Supplied What changes have we seen? Since my first long expedition in 2007 to the Russian Arctic, I have seen increasing evidence of rapid thawing of permafrost. What is clearer is the increasing frequency of strong fires and really hot summers in Siberia and Canada. Interactions between these climate extremes and fires are accelerating melting. That is very worrying. After a very warm summer, new lakes are seen in the following years. Are there benefits to thawing permafrost? There may be some small benefits, such as expanding agricultural frontiers and opening up mineral resources, but they in no way outweigh the negative impacts. In reality, thawing permafrost will make access to resources in the Arctic much more difficult because the ground will become more unstable. That will make it more expensive and difficult to extract something. Infrastructure in Canada and Alaska will be affected, but Russia will be hit the hardest. Half of Russia’s oil and gas comes from permafrost areas, which are not going to do well for a couple of decades. The Russians are also beginning to realize that they will not be able to expand agriculture into permafrost areas for a long time because suddenly food cannot be grown on forested soils. Therefore, the economic damage from thawing permafrost will be enormously greater than the economic benefits. What can be done? Unfortunately, there are no viable large-scale geoengineering solutions. The only way to limit the melting of millions of square kilometers is to rapidly reduce emissions. We need to act urgently. For every degree of global warming we limit, we prevent 4 million square kilometers of permafrost from melting and releasing greenhouse gases. The greater our action to reduce emissions, the easier the challenge will be. And vice versa. It’s a feedback loop: the more we disrupt the Earth system, the more it will emit on its own, making the challenge even more dire. How much scientific uncertainty is there? The fact is that this is a big problem. It is virtually certain that a large amount of CO2 and/or methane will be released. We are confident in the processes and feedback. Global warming is up to four times greater in the Arctic than the global average and we are also virtually certain that it will accelerate. What is less clear is the precise rate of change and whether we will enter wetter or drier roads, which will determine how much methane or CO2 will be released. What do you think of your research? Even in isolation, it’s really worrying. Then there is a growing understanding that permafrost is just one of many tipping-point processes that are irreversible. The damage we are causing now will mean that the Earth will continue to emit greenhouse gases for centuries. So it’s not just my children, it’s five, six, seven, ten generations of humans that will have to deal with the problems we are creating now. To me, this is an obvious truth, which is why it’s frustrating that we can’t communicate the urgency of what we know well enough to drive action. I don’t believe humanity will be wiped out, but many people will suffer greatly and unnecessarily due to the combination of these cascading effects. That’s worrying and really sad.
