Climate change: coldest place on earth is on fire, it’s getting worse

A study led by researchers from the CSIC and CREAF, and published in Science, shows that rising temperatures have caused an exponential increase in fires in the Arctic.

In the years 2019 and 2020, an unusual number of fires were recorded in the Arctic. This set off alarms in the scientific community since in the Arctic there are large areas of permafrost peat bogs, a permanently frozen subsoil layer that accumulates large amounts of carbon.

Fires deteriorate permafrost and contribute to the emission of carbon in the form of greenhouse gases. The unknown until now was whether this increase in fires in 2019-2020 was punctual or if it is a trend that will continue to increase due to the warming of the Arctic.

Global warming fuels frequent wildfires

“In 2020 alone”, details Adrià Descals, first author of the work, “423 fires were detected in the Siberian Arctic, which burned some three million hectares (an area almost equivalent to that of all of Belgium), which caused the emission of 256 million tons of CO 2 equivalent”. The researcher adds that "with future warming, these large fires will be repeated at the end of the century and will have different implications, both for the Arctic and for the global climate."

The authors have quantified, from satellite observations from 1982 to 2020, the area burned in Siberia above the Arctic Circle, a region that covers 286 million hectares. "While observations indicated that the 2020 fire season was exceptional, no precise quantitative assessment had been done in this remote region until now," comments co-author David Gaveau.

In this work, the scientists show that the risk factors for fires associated with temperature have increased in recent decades and that there is an exponential relationship between the area burned annually and these factors.

4.7 million hectares burned in 2 years

"Temperatures are reaching a critical threshold in which small increases above the summer average of 10 °C can exponentially increase the area burned and the associated emissions," explains Josep Peñuelas.

The summer of 2020 was the warmest in four decades and the large area burned between 2019 and 2020 is unprecedented, the authors explain. Between 2019 and 2020, some 4.7 million hectares were burned, which meant total emissions of 412.7 million tons of CO 2 equivalent.

“In 2020, fires were detected above the 72nd parallel north, more than 600 kilometres north of the Arctic Circle, in areas where fires are unusual and where winter snow was still visible at the start of the fires,” he explains. “Many fires were detected just a few days apart, so we hypothesized that increased dry storms and lightning are the main cause of the fires, although more research is needed to show the extent to which human activities in this remote region can influence these fires.

Increased air temperature and risk of fire

Several of the factors that can exacerbate fire risk have increased significantly, and all of these factors are related to rising temperatures. Factors such as drier weather conditions, longer summers and more vegetation have shown a consistent trend over the past four decades, the authors say.

The authors note that "the average summer temperature of 2020 - which was 11.35 degrees - will be very common from the second half of the century if Arctic warming continues at the same rate." As the first author, Adrià Descals warns, "these temperature anomalies increase fire risk factors, so the conditions that gave rise to the 2019 and 2020 fires will be repeated in the Arctic at the end of the century."

An explanatory model of how the factors are chained

In 2019 and 2020, fire rates in the Siberian Arctic exceeded those of the last four decades. In 2020 alone, there were seven times more fires than the average since 1982, damaging an unprecedented peatland area. Josep Peñuelas explains that "the concatenation of these factors has generated this increase in the rate of fires".

"Higher temperatures account for earlier ice melting, which allows for more vegetation growth and increases fuel availability."

"When there is more vegetation and earlier, the availability of water in the soil decreases and the plants suffer greater water stress," says Aleixandre Verger, a researcher at the CSIC and CREAF.

In 2019 and 2020, fire rates in the Siberian Arctic exceeded those of the last four decades

In turn, “extreme heat waves, such as 2020 one in the Siberian Arctic, increase vulnerability to drought, as they can dry out plants and reduce peat moisture, thereby increasing fire intensity and carbon emissions".

On the other hand, heat waves and, above all, the increase in surface temperature, can increase convective storms and lightning, which, although they are rare phenomena in the Arctic so far, "are expected to increase as the climate improves."

"Climate warming, therefore, has a double effect on the risk of fires: it increases the susceptibility of vegetation and peat bogs to fire and, on the other hand, it increases the number of ignitions caused by electrical storms," ​​explains Adrià Descals.

The work suggests that the Arctic is already experiencing a change in fire regimes caused by climate warming. "Areas burned in 2019 and 2020 could be one-off events, but recent temperature trends and projected scenarios indicate that by the end of the century, large fires like those in 2019 and 2020 will be frequent if temperatures continue to rise at current rates."

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