Deadly, record-breaking heatwaves will persist for 1,000 years, even under net zero

Deadly hotter and longer heatwaves, which worsen in severity the longer it takes to reach net zero carbon emissions, will become the norm predicts new climate research.

Published in Environmental Research: Climate, researchers at the ARC Centre of Excellence for 21st Century Weather and CSIRO used climate modelling and supercomputers to understand 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.

University of Melbourne Dr Andrew King, who co-authored the paper, said throughout all scenarios, the longer net zero is delayed, the higher the occurrence of historically rare and extreme heatwave events.

“This is particularly 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,” Dr King said.

The study showed heatwaves as 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 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.

Professor Sarah Perkins-Kirkpatrick from the Australian National University and lead author said the work challenges a 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 future, allowing effective and permanent adaptation measures to be planned and implemented,” Professor Perkins-Kirkpatrick said.

“It is still vitally important we make rapid progress to permanent net zero, and reaching global net zero by 2040 at the latest will be important to minimise the heatwaves severity.”

Dr King said the findings call for immediate action on reducing emissions and planning for adaptation.

“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,” Dr King said.