杏吧原创

Smoke pollution from Australian bushfires in 2019 and 2020 warmed the stratosphere over the southern hemisphere by at least 1掳C for six months, according to a new analysis.

The devastating 2019 to 2020 bushfire season in Australia injected huge amounts of smoke into the stratosphere and led to record aerosol pollution.

Yu Pengfei at Jinan University in China and his colleagues used a climate model to simulate the atmospheric smoke movement during the fires and its environmental impacts. The model looked at aerosol movement, microphysics and chemistry in from Earth鈥檚 surface up to 45 kilometres into the atmosphere.

The researchers found that the smoke remained in the stratosphere for all of 2020, measurably warming the stratosphere by between 1 and 2 掳C, which persisted for approximately six months after the fires.

The particles in the bushfire smoke were mainly comprised of organic carbon and black carbon. 鈥淭he black carbon material in smoke can absorb sunlight and warm the surrounding air,鈥� says Yu. The stratospheric warming would have led to changes in air circulation for the six months in which the warming persisted, but the exact effects are unknown, he says.

The stratosphere 鈥� the portion of the atmosphere roughly between 10 and 50 kilometres above Earth鈥檚 surface 鈥� also contains the ozone layer. The researchers suggest that the smoke particles also increased the destruction of ozone molecules over the southern hemisphere, reacting in a similar manner to sulphate aerosols.

The heating effect of the black carbon would also have contributed to the increased rate of ozone destruction, says Yu. This is likely to have been part of why the ozone hole was larger than usual in 2020.

The researchers鈥� model estimated that between August and December 2020, there was a drop of 10 to 20 Dobson units in total column ozone, a measure of the amount of ozone extending vertically upwards from Earth鈥檚 surface. The average amount of ozone in the atmosphere is roughly 300 Dobson units.