The massive fires of 2019 to 2020 had global impacts. The heat of the fires was so intense they punched smoke and greenhouse gases through the troposphere to the stratosphere where the lifetime of the smoke is ten times what it would be in the lower altitudes. It also spread over most of the southern hemisphere and can contribute to dangerous climate effects.

This disturbing study shows that we need to manage forest fire fuels better by doing much more prescribed burning. ‘Cool’ fires during the non-summer months emits far less smoke than wildfires, and do not force the smoke plumes into the troposphere. Cultural burning in Traditional ways can contribute to better management of forest fuels.

Prescribed burning is planned and warnings can be issued to local areas so that people with asthma can be fore-warned and take precautions. The wildfires of 2019-20 left people with no option and in many cases no escape from the smoke.

In southern Australia, global heating has reduced the prescribed burning season to a narrow cool window, so that it is more difficult to light fires safely to reduce fire fuels. This leaves a problem for fire fighters and managers that has to be resolved urgently by employing more fire practitioners to light more cool-season burns."

Secondary points:
“Prescribed savanna burning in the cooler dry seasons has reduced the number of wildfires by an enormous amount, and they emit much less greenhouse gases. Indigenous rangers get paid to do this work by claiming carbon credits for the reduced emissions.

The authors state that the southern summers are dry, and while that’s true in southern Australia, the northern summers are wet. Most burning in northern Australian savannas is carried out in the early dry season (the southern winter) from March or April until early July to prevent wildfires later in the hot dry season.”

General comments:
"Para 3 p1 fire season in savannas of northern Australia is generally from April to December, but recent years since the implementation of the savanna burning program to reduce emissions from hot late-dry season fire (from 1st July onwards when the dry season heats up) has reduced late-season fires substantially.

The Southern hemisphere summer is not uniformly dry, and the monsoonal region is actually the wet season in summer. Southern Australia experiences more dry summers and wet winters. The fire seasons are actually reversed from north to south, with the main fire season in the northern savannas being during the southern winters, and the southern summers experiencing the majority of fires.

Australia is joining those suffering regions of the Earth such as the Amazon basin and Southeast Asia—where out-of-control wildfires are scarring landscapes, killing biodiversity and driving distressed people to hospital in respiratory crisis.

As Australians, we’ve become used to watching the world battle wildfire calamities.  But with mounting numbers droughts and heatwaves and many land-use changes here in Australia, we’re increasingly in the path of major infernos ourselves.

The 2019/20 bushfire season, the Black Summer, was characterised by a large number of fires that burnt over a vast geographical area. Many of these fires escalated into extreme bushfires, i.e. fires that exhibit intense and expansive flaming and that strongly couple with the atmosphere. Over 30 of these fires developed into pyrocumulonimbus (pyroCb), which have the potential to inject smoke and other particulates into the upper troposphere and lower stratosphere. While large pyroCbs have occurred in historical bushfire events such as the 2003 Canberra fires and the 2009 Black Saturday fires, the number that occurred in 2019/20 was absolutely unprecedented. The severe drought over southeast Australia, the recurring episodes of critically low fuel moisture content and the repeated occurrence of extreme fire weather associated with heatwaves and frontal systems resulted in the perfect conditions for these firestorms to form. It is therefore unsurprising that record-breaking levels of atmospheric aerosols were observed in the aftermaths of these bushfires.

Further evidence that bushfire seasons are becoming more extreme and are impacting the global climate system. While there may be a transient cooling effect of smoke pollution the enormous emissions contribute to global heating through enduring greenhouse gases.  A concerning question is whether Australian forests are becoming sources rather than sinks of carbon, accelerating climate change.

Our Black Summer bushfires were so big and so consequential that they altered the climate.  Enough smoke and ash were injected into the atmosphere that it resembled a volcanic eruption.  This sobering research finding should erase any lingering doubt about the gravity of both what happened and what can happen again in the future.  Research findings such as this serves to remind us all that what happens in one place can impact the entirety of the planet.  As scientists continue to study the Black Summer bushfire impacts across Australia we will see what the recovery looks like and gain the insights needed to conserve our unique biodiversity.