Fortunately we have the data. Scientific analysis shows that the primary driver of rainfall and therefore drought and bushfire risk in Australia are four separate but sometimes linked weather patterns in the Pacific, Indian and the Antarctic Ocean.
These weather patterns are: the Southern Ocean Oscillation (ENSO), particularly when El Nino weather patterns cross the Pacific; the longer-term Pacific Oscillation (IPO) which impacts ENSO events; the Indian Ocean Diopole (IOD); and the Southern Annular Mode (SAM).
In simple terms, sea temperatures in the Pacific, Indian and Antarctic Oceans directly influence our annual weather cycles and drive surface temperatures and rainfall across Australia.
When these weather cycles are positive, rainfall is lower and the risk of drought and summer bushfires are higher, and when they coincide, the risk of a prolonged and severe drought and bushfires is much higher.
These weather patterns are regularly monitored by the CSIRO and Bureau of Meteorology and provide corporate Australia and government decision makers with effective forward-looking indicators of drought and bushfire risk each year.
In the past 12 months, an El Nino weather pattern in the Pacific Ocean and the IDO in the Indian Ocean have both been positive, a dreadful combination that provided the platform for the recent drought and bushfires across Australia.
To be fair, while we knew the risk, we still did not know the exact location, timing, duration and intensity of the droughts and bushfires that would actually occur.
Some have argued that the unprecedented extent and ferocity of the recent drought and current bushfires across Australia is due to human-induced climate change. However, historical analysis shows Australia has suffered many big droughts and bushfires.
The 1974-75 bushfires in outback NSW, Queensland, South Australia, Western Australia and the Northern Territory burnt 117 million hectares compared with 8.4 million hectares burnt so far in 2019-20.
As the early 1970s fires were well away from metropolitan areas, did not affect holiday-makers, did not destroy many houses and did not kill as much livestock, they did not have a big emotional impact.
Research by Danielle Verdon-Kidd and Anthony Kiem in 2009 found that the three big droughts in Australian history, the Federation Drought between 1895 and 1902, the WWII drought between 1937 and 1945 and the Big Dry or Millenium Drought between 1997 and 2009 were all directly caused by ocean weather cycles.
The research shows that the direct causes of each drought was different. The Federation Drought occurred during sustained ENSO and El Nino activity in the Pacific Ocean, the IOD is thought to have been the major driver of the WWII Drought and the SAM was the major causal factor in the Big Dry.
Not enough was known about the impact of the ocean weather patterns to prepare for the Federation Drought or the WWII drought but the impact of these weather cycles was well known ahead of the Big Dry and the recent drought and bushfires.
As satellite monitoring and improved weather modelling is improving, there is simply no excuse for business executives and board directors or government decision makers to be unprepared for extreme weather events each year.
Some argue that human-induced climate change has brought forward, or is increasing the frequency and intensity of El Nino and IOD impacts and therefore drought and bushfire risk in Australia.
Research by Sarah Harris and Chris Lucas in 2019 found that ocean weather cycles do not explain the rising average temperatures and lower rainfall in south-east Australia over the last 45 years and they suggest human-induced climate change is probably driving this.
However, the Harris and Lucas research conclude: “The dynamics of global warming and its interactions with modes of inter-annual and decadal variability and its effects on fire weather in Australia remain uncertain”.
This conclusion does not invalidate the theory about the impacts of human-induced climate change on our weather it just means we do not have enough information yet for sound risk management or policy development.
Verdon-Kidd and Kiem also concluded: “Further understanding into how multiple physical mechanisms, including anthropogenic climate change, interact to drive south east Australia climate … is required … Failure to address these issues will result in drought management strategies continuing to be largely ineffective in reducing Australia’s vulnerability to drought.” The same logic applies to bushfires or cyclones and floods.
Any inquiry or policy response into the recent bushfires must address this issue. We urgently require further scientific work to provide greater certainty about the interaction between ocean weather events and the location, timing, duration and intensity of human-induced climate change. Only then will we have sufficient data to make sound long-term business and policy decisions.