Researchers from the University of Southern Queensland (USQ), University of Oxford, University of Edinburgh and Stockholm University, examined the devastating 'Dust Bowl' era in the USA and compared it to present day conditions.
Lead author Tim Cowan is a researcher with USQ's Centre for Applied Climate Sciences, working on the Queensland Government's Northern Australia Climate Program (NACP).
"The 1930s heatwaves in America were thought to be extremely rare events (once in a hundred years)," he said.
"Our analysis shows that under today's levels of greenhouse gases they are more than twice as likely to occur, with their period of return reducing to once in around 40 years.
"We focused our study on the direct impact of greenhouse gases on the historical heatwaves, although the model does not fully account for the wide-spread land changes and crop failures across the Great Plains during the drought."
The study used a climate model developed at the University of Oxford that does not run on supercomputers but on the personal computers of volunteers from around the world.
University of Edinburgh's Gabi Hegerl said 1936 still held the record for the hottest year in the continental US.
"But the country is tracking towards ever warmer summers, and globally, this level of extreme heat has become the new normal,' she said.
"With summer heat extremes expected to intensify over the US throughout this century, it is likely that the 1930s records will be broken in the near-future."
Friederike Otto, acting director of the University of Oxford Environmental Change Institute, said if extreme heatwaves and drought reduce the vegetation as they did in the 1930s, heatwaves could become even stronger.
"This would have dire consequences not only for the US but for global food systems," she said.
"The results of this research show that this scenario is more likely than ever, and should urge us to develop and implement more ambitious adaption and mitigation plans."
The paper was published in Nature Climate Change and is available at https://www.nature.com/articles/s41558-020-0771-7.
