Thunderstorms caused by Australian bushfire smoke are likely to have pumped as much smoke into the stratosphere as a volcanic eruption.The flames across the countryhave been so intense in recent weeks that they have created their own weather. They create rising air mixed with ash and smoke, resulting in storm clouds over the fires. These clouds are called pyrocumulonimbus (pyroCbs). There were at least 20 PyroCbs between December 28th and 31st and even more on January 4th.
Some of them are powerful enough and rise high enough to send smoke into the stratosphere. NASA says these plumes of smoke have now completely circled the Earth.
The extent of the smoke in the stratosphere has now been calculated by David Peterson of the US Naval Research Laboratory, who presented his preliminary results to the American Meteorological Society at a meeting in Boston.
“The key thing here is really the impact this has on the stratosphere,” he says. Although the 1991 eruption of Mount Pinatubo, the largest in modern history, is not as large, the effect is similar to a more moderate volcanic eruption, Peterson said.
While it is known that a volcanic eruption can release enough aerosols into the atmosphere to have a cooling effect, due to the different chemistry of PyroCbs, the impact of fires on global temperatures is not yet entirely clear.
They can have a warming or cooling effect, and it is not known how long the smoke lasts at altitudes between about 10 and 50 kilometers, roughly where the stratosphere begins and ends. According to Peterson, the biggest question is what role ProyCbs play in the climate system. Some of the smoke plumes also become high enough to deplete the ozone layer.
According to Alan Robock of Rutgers University in New Jersey, a potential cooling effect from wildfire smoke is unlikely on a global scale, but could result in several degrees Celsius of cooling on a local scale.
However, bushfire smoke can remain in the stratosphere for half a year or longer because at such altitudes it can be warmed by the sun and poured further upwards, extending its lifespan.
Our knowledge of PyroCbs is still at an early stage. These thunderstorms and the smoke they bring into the stratosphere have only been detectable with satellite instruments since the early 2000s. They were previously thought to be the result of volcanic eruptions until analysis attributed them to forest fires.
