Arctic 'megafires' the size of Belgium released 256 million tonnes of CO2, scientists now know why
Scientists claim a rise in global temperatures is causing an exponential spike in Arctic "megafires," providing new insight into the cause of a 3-million-hectare burnt area in the Siberian Arctic. The new study was published today (Nov. 3) in Science.
The research suggests that the Arctic's fire regimes are already shifting due to the climate's warming, which could impact how much carbon dioxide is released into the atmosphere. Better yet, we can expect megafires to become more frequent by the end of the century if temperatures continue to climb at the current rate.
Satellite data 'chips' deeper into an unusually high number of fires in the Siberian Arctic between 2019 and 2020
In 2019 and 2020, there were an unusually high number of fires in the Siberian Arctic. The scientific community was alarmed by this since the Arctic contains substantial stretches of permafrost, a permanently frozen layer of subsoil that stores much carbon. Permafrost is damaged by fires, which also cause greenhouse gas emissions that contain carbon.
Unresolved was whether the rise in flames in 2019–2020 was a one-off or indicative of a trend that may worsen as the Arctic warms.
Using satellite measurements from 1982 to 2020 on a region burned in Siberia, a group of international researchers under the direction of Adrià Descals and Josep Peuelas (both from the Spanish Council for Scientific Research (CSIC) set out to analyze and quantify the associated CO2 emissions. This region lies above the Arctic Circle and covers 286 million hectares.
Satellite measurements revealed a link between fire risk and rising temperatures over past four decades
The study found that approximately 4.7 million hectares were burned between 2019 and 2020, resulting in total emissions of 412.7 million tonnes of CO2 equivalent.
"In 2020 alone, 423 fires were detected in the Siberian Arctic, which burned around 3 million hectares (an area almost as big as the whole of Belgium) and caused the emission of 256 million tonnes of CO2 equivalent," explained Descal in a press release. This sum is similar to Spain's total annual CO2 emissions.
The authors argued that 2020's summer was the warmest in four decades, leading the size of the area burned between 2019 and 2020 to be unprecedented. Fundamentally, the scientists demonstrate an exponential link between the amount burned annually and fire risk factors associated with temperature.
"Higher temperatures explain the earlier thaw, which in turn allows for greater vegetation growth and increases fuel availability"
Risk factors include drier weather conditions, longer summers, and more vegetation, which the study also indicates have increased over the past four decades.
"Higher temperatures explain the earlier thaw, which in turn allows for greater vegetation growth and increases fuel availability. The fact that there is more and earlier vegetation reduces the availability of water in the soil, and plants suffer greater water stress," explained Aleixandre Verger, a researcher at CSIC.
In turn, "extreme heat waves, such as in 2020 in the Siberian Arctic, increase vulnerability to drought, as they can desiccate plants and reduce peat moisture, and therefore increase the intensity of fires and carbon emissions".
A double effect: In addition to the fire risk of Arctic vegetation, rising temperatures can increase thunderstorms
On the other hand, heat waves, and especially the rise in surface temperature, can potentially intensify convective storms and lightning, which have been highly unusual in the Arctic up until now. Still, the scientists claim, "they are expected to increase as the climate warms."
"By the end of the century, large fires such as those in 2019 and 2020 will be frequent"
Our work suggests that the Arctic is already experiencing a change in fire regimes caused by climate warming. "Recent temperature trends and projected scenarios indicate that, by the end of the century, large fires such as those in 2019 and 2020 will be frequent if temperatures continue to increase at the current rate," concluded Adrià Descals and Josep Peñuelas.
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