Cape Town - A new study explaining extreme events of 2021 from a climate perspective has found that the devastating UCT/Devil’s Peak fire that raged in April 2021, saw the most severe autumn fire weather conditions in Cape Town since 1979, and that these fire weather conditions are 90% more likely to occur now.
The study, titled “The April 2021 Cape Town Wildfire: Has Anthropogenic Climate Change Altered the Likelihood of Extreme Fire Weather?”, forms part of a special collection of the Bulletin of the American Meteorological Society titled “Explaining extreme events of 2021 from a climate perspective”.
The study was done by lead author Zhongwei Liu, from the University of Coventry in the UK, who is doing her PhD on attributing weather conditions associated with extreme wildfire events to climate change, along with Jonathan Eden, Bastien Dieppois, and Matthew Blackett from Coventry, and UCT Climate System Analysis Group PhD student Stefaan Conradie.
Conradie said: “Using four current generation (CMIP6) climate models, we found that the fire weather conditions associated with the April 2021 Cape Town wildfire are 90% more likely now in a warmer world (and will happen roughly two times as often).
“It is therefore reasonable to expect weather conditions under which fire-fighting becomes extremely challenging to happen ever more often on the mountains around Cape Town.”
Conradie said that weather factors were rarely responsible for starting fires around Cape Town (the April 2021 fire, for example, was very likely started by arson, according to a SANParks-commissioned report), but together with available fuel loads (flammable vegetation), weather conditions determine when fires can be easily controlled or suppressed, and when they become essentially uncontrollable.
“This is when fires can pose a huge risk to human lives, structures and health. Unprecedented fire weather conditions can be particularly dangerous, as they may lead to fire behaviour not previously observed by fire fighters,” Conradie said.
Enviro Wildfire investigator Rob Erasmus prepared a summary report on events and matters relating to the Devil’s Peak fires of April 18, 2021.
In the report, Erasmus said extremely low humidity coupled with an increase in wind speed and a change in the wind direction caused embers, carried in the warm smoke column, to land outside the burn area, where they ignited the surrounding veld. The dry vegetation and wind then caused the fire to spread rapidly over a wide front.
“The primary reason for loss being suffered from this fire event was due to windblown embers landing on dry fuels (thatched roofs, pine and palm trees, ivy, leaves in gutters) that set them alight, resulting in buildings catching on fire,” Erasmus said.
Regarding the implications of the study, Conradie said they showed that the weather and climate-driven risk of uncontrollable fire behaviour around Cape Town in autumn was increasing. The conditions in 2021 were unprecedented; there could be no past experience of fighting fire in such conditions.
“Climate change will likely see unprecedented conditions occurring in future. Thus, managing this risk is becoming more urgent,” Conradie said.