Largest stratospheric smoke injection by a wildfire event

In December 2019/January 2020, Australia witnessed unprecedented bushfires which burned an area of some 5.8 million ha (14.3 million acres), affecting around one-fifth of the country's temperate forest. The event also induced a series of intense pyrocumulonimbus (pyroCb) clouds in the skies above the blazes, stretching many kilometres into the sky. It’s estimated that the 2019-20 Australian bushfires injected between 0.4 ± 0.2 Tg (teragrams) - i.e., 400,000 tonnes (440,000 US tons) - of aerosol particles (a mix of carbon particles, smoke and condensed water) into the lower stratosphere, which is equivalent to the output of a moderate volcanic eruption. The findings of this research were published in the journal Nature on 21 September 2020.

The most intense pyroCb activity of the period was recorded on New Year's Eve; on 1 Jan 2020, the smoke cloud was detected reaching an altitude of 17.6 km (10.9 mi) and covering an area of 2.5 million km2 (965,255 sq mi). Over a period of three months following the fire outbreak, smoke would reach as high as 35 km (22 mi) into the stratosphere.

PyroCbs, or cumulonimbus flammagenitus (aka CbFg), are a recently recognized phenomena generated by updrafts of heat and smoke in particularly intense wildfires. These powerful funnels draw up great quantities of water vapour, along with ash and other particulates, to form massive cloud columns, which in turn develop into thunderstorms with little precipitation and lightning that can go on to spark further fires.

The Australian bushfires almost trebled the size of the previous largest wildfire smoke injection on record: the "Pacific Northwest Event", which saw forest fires burn over British Columbia, Canada, and Washington State, USA, in Aug 2017 was estimated to have sent between 0.1 and 0.3 Tg (100,000–300,000 tonnes; 110,000–330,000 US tons) of smoke aerosol particles into the lower stratosphere.