Media release

From: ARC Centre of Excellence for 21st Century Weather

Deadly, record-breaking heatwaves locked in for 1,000 years, even under net zero pathways

We must prepare for a future of frequent, deadly heatwaves, which will worsen in severity the longer it takes to reach net zero, new research has shown.

Researchers working at the ARC Centre of Excellence for 21st Century Weather and Australia’s national science agency CSIRO used climate modelling and supercomputers to learn how heatwaves will respond over the next 1,000 years, after the world reaches net zero carbon emissions.

They chose a range of dates between 2030 and 2060, and calculated the long-term difference in heatwaves for each five-year delay in reaching net zero.

Heatwaves were shown to be systematically hotter, longer and more frequent the longer net zero is delayed. Heatwaves may even be exacerbated by long-term warming in the Southern Ocean even after net zero is reached.

Most trends in the data showed no decline over the entire 1,000 years of each simulation, indicating that heatwaves do not start to revert back towards preindustrial conditions even when net zero is reached, for at least a millennium.

Some regions even displayed heatwaves of significantly increasing severity when net zero occurs by 2050 or later.

Throughout all scenarios, the longer net zero is delayed, the higher the occurrence of historically rare and extreme heatwave events.

This is problematic for countries nearer the equator, which are generally more vulnerable, and where a heatwave event that breaks current historical records can be expected at least once every year or more often if net zero is delayed until 2050 or later.

The research demonstrates the importance of reaching global net zero by 2040 at the latest to minimise the severity of future heatwaves.

Professor Sarah Perkins-Kirkpatrick of the Australian National University, the lead author of the paper, said: “Our work challenges the general belief that conditions after net zero will begin to improve for future generations.

“While our results are alarming, they provide a vital glimpse of the long-term future, allowing effective and permanent adaptation measures to be planned and implemented. It’s also vitally important that we make rapid progress to permanent net zero.”

Dr Andrew King of the University of Melbourne, a co-author on the paper, said: “Investment in public infrastructure, housing, and health services to keep people cool and healthy during extreme heat will very likely look quite different in terms of scale, cost and the resources required under earlier versus later net zero stabilisation. This adaptation process is going to be the work of centuries, not decades.”

The research has been published in the journal Environmental Research Climate and is available here.