Record heatwaves may become much more common, says study

Abnormally hot weather could be up to seven times more frequent in the world with climate change, scientists say

The smouldering path of the Bootleg Fire on July 17 near Klamath Falls, Oregon, in the US. AFP

Cyprus, Cuba, Turkey, Canada, Northern Ireland and Antarctica all recorded their hottest temperatures in the past two years, and a new study suggests more such extremes are coming.

In the next three decades, "record-shattering" heatwaves could become two to seven times more frequent in the world than in the past 30 years, a report published on Monday in the Nature Climate Change journal says.

Beyond 2050, if current greenhouse gas emission trends continue, such hot spells could be three to 21 times more frequent, the study found.

"We haven't seen anything close to the most intense heat waves possible under today's climate, let alone the ones we expect to see in the coming decades," said co-author Dr Erich Fischer, a scientist at ETH Zurich.

For the study, the researchers used climate modelling to calculate the likelihood of record-breaking heat that lasted at least seven days and far passed earlier records.

Communities preparing for climate change need to be ready for such extremes, Dr Fischer said.

"Every time record temperatures or precipitation go well beyond what we've experienced during our lifetime, that's usually when we're unprepared and the damage is largest," he said.

Last month's Canadian heatwave killed hundreds of people and reached 49.6°C, 4.6°C above the country's previous record, set in 1937.

"We should no longer be surprised if we see records smashed by large margins," Dr Fischer said.

If greenhouse gas emissions are aggressively cut, the likelihood of heatwaves would remain high but the chances of exceeding records would eventually drop over time, the study suggests.

"We must expect extreme event records to be broken, not just by small margins but quite often by very large ones", said climate scientist Dr Rowan Sutton, of the University of Reading's National Centre for Atmospheric Science.

"This highlights the huge challenge to improve preparedness, build resilience and adapt society to conditions that have never previously been experienced."

The study was released as scientists with the Intergovernmental Panel on Climate Change begin two weeks of online meetings to finalise their next global climate science assessment.