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Drought can have dramatic consequences in Australia; It can destroy agriculture, threaten water supplies and destroy the environment. Large parts of Australia are prone to drought and the
Drought can have dramatic consequences in Australia; It can destroy agriculture, threaten water supplies and destroy the environment. Large parts of Australia are prone to drought and the risk is expected to increase as global warming continues. Therefore, it is important for Australia to be prepared for droughts that last especially for many years.
To get an idea of how bad things could get, we need to look far back in time to see what happened before.
We checked computer simulations of Earth’s climate over the past 1,150 years. Worryingly, we found that given enough time, natural variability in Australian rainfall can lead to “mega droughts” lasting 20 years or more. This, combined with human-caused climate change, means future droughts will be much worse than we think.
We need historical rainfall data to understand the full picture of future droughts. However, in Australia these records date back to about 1900. This does not fully cover the enormous range of natural rainfall variability that occurs over hundreds of years.
We can derive these long records to some extent from environmental features such as trees, which record information about precipitation changes in their annual growth rings. Unfortunately, these natural “archives” often date back only a few hundred years. And they only keep information about what’s happening in their area, not across Australia.
Scientists need alternative ways to look into the past, and that’s the purpose of our new study. We used computer models of Earth’s climate over 850 to 2000 years (1150 years total) to fill in the picture. The models simulate the interaction between the atmosphere, oceans, ice and land, providing a picture of how climate changes over time.
Because no climate model is perfect, we used an ‘ensemble’ of 11 different climate models to examine the diversity of droughts experienced in Australia.
We first considered the characteristics of droughts resulting from natural changes in rainfall in Australia. We then compared simulated droughts in the 20th century with droughts in the pre-industrial period (before 1850). This will allow us to test whether human-caused climate change over the past century has caused significant changes in Australian droughts.
We paid particular attention to the Murray-Darling Basin in southeastern Australia. It contains Australia’s largest river system and is our largest agricultural region so it is important to know how severe droughts can be.
We find that during the 20th century, simulated droughts in southwestern and eastern Australia, including the Murray-Darling Basin, were on average longer than in pre-industrial times.
This change is consistent with future rainfall trends expected in these regions due to human-caused climate change. This shows that new human impacts on our climate are already making southern parts of Australia more prone to drought.
Other characteristics of modeled Australian droughts, such as their intensity or recurrence, did not differ significantly over the past century compared to pre-industrial times. In other words, human-caused climate change has probably not yet caused greater droughts or changes in drought frequency in Australia. But this impact could still occur as climate change worsens.
The devastating effects of the last major drought in Australia from 2017 to 2019, known as the ‘belly drought’, are a stark reminder of what we can expect in the future. The drought was likely worsened by human-caused climate change and preceded the devastating Black Summer fires.
One of the most worrying findings of our research is that even without the effects of climate change, natural variability could cause ‘mega droughts’ in Australia lasting 20 years or more. This is far longer than any drought Australia has experienced since instrumental recording began.
Our findings show that megadroughts are possible on the Australian continent. This includes the Murray-Darling Basin, where typical droughts of the last century lasted four to five years. The graph below shows the worst direct precipitation since they began to be recorded. A 20-year drought would make these extreme events short-lived.
This new study shows that major droughts are possible in Australia even without the effects of climate change. These are a natural part of Australia’s long-term rainfall variability. This conclusion is supported by evidence from ice cores showing a 39-year drought that affected eastern Australia approximately 800 years ago. This is a concern because climate change also increases the likelihood of reduced rainfall across much of southern Australia.
It is difficult to imagine a drought lasting several decades. But our research shows that it can happen, and that future droughts in Australia will be worse than those seen in our recent experience. Our study highlights the need to consider the unthinkable when it comes to preparing for future droughts. This has implications for industry, governments and communities as they adapt to a warmer future.
Source: Port Altele
As an experienced journalist and author, Mary has been reporting on the latest news and trends for over 5 years. With a passion for uncovering the stories behind the headlines, Mary has earned a reputation as a trusted voice in the world of journalism. Her writing style is insightful, engaging and thought-provoking, as she takes a deep dive into the most pressing issues of our time.
