Heavy rainfall and widespread flooding across Australia’s east coast from 2020 to 2022 was exacerbated by the Black Summer bushfires, a new study has found.

The research links bushfire smoke to extra cloud cover over the southeastern Pacific Ocean and cooler sea surface temperatures, which then influenced La Nina.

Eastern Australia experienced several years of disastrous flooding during the cold weather event.

The model-based study from the National Center for Atmospheric Research in the US was published in Science Advances. 

It shows the Black Summer bushfires in 2019 to 2020 emitted as many aerosols into the atmosphere as major volcanic eruptions.

UNSW academic and Aon insurance senior analyst Tom Mortlock said the findings were significant because until now a lot of research in the area was based off historical events.

“It’s the first time that we’ve been able to look at the influence of a bushfire event that has been large enough to have this kind of effect and has occurred in recent history,” he told AAP.

Dr Mortlock was not involved in the research, but said the findings highlighted how conditions across the entire planet are connected with the Pacific Ocean, where La Nina and warmer El Nino develop.

“It doesn’t just affect Australian weather, it also affects what’s going on in the US, it affects weather in Europe, it’s the primary mode of global climate variability,” he said.

Dr Mortlock warned that after years of above-average rainfall and fewer bushfires, there was now a significant amount of fuel growth ready to burn when warm weather comes along.

“There’s certainly going to be a heightened bushfire risk if El Nino is declared this spring or summer,” he said.

By Rachael Ward in Melbourne

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