A child cools off in the fountain at Grand Park in downtown Los Angeles. Picture: Zhao Hanrong/Xinhua

New York - The death toll from heatwaves could rise by up to 2 000 percent in some parts of the world by 2080, according to a study released on Tuesday, as large parts of the northern hemisphere reeled from unusually high temperatures.

Scientists have long warned that climate change will bring more extreme weather across the globe, from heatwaves to hurricanes.

The researchers behind the latest study say it is the largest yet on the death toll of heatwaves, which they predict will increase in frequency and severity.

"Future heatwaves, in particular, will be more frequent, more intense and will last much longer," said Yuming Guo, associate professor at Australia's Monash University, in a statement.

"If we cannot find a way to mitigate the climate change (reduce the heatwave days) and help people adapt to heatwaves, there will be a big increase of heatwave-related deaths in the future."

Heat waves sweeping through the northern hemisphere have dominated the news in recent weeks, with dozens of deaths registered from Japan to Canada.

The study, published in the online journal PLOS Medicine, looked at 20 countries on four continents and found the rise in mortality was likely to be highest near the equator.

Hardest-hit Colombia could suffer 2,000 percent more premature deaths from extreme heat during the period of 2031 to 2080 compared with 1971 to 2010, it said.

The Philippines and Brazil were also likely to see large increases in numbers of premature deaths, it found.

Countries located further from the equator such as the United States and European nations would see smaller hikes.

However even under best-case scenarios - where planet-warming emissions were curbed and population increases low - deaths would increase, the study found.

During heatwaves, defined as at least two consecutive days of abnormally hot temperatures, the body cannot dissipate heat, leaving older adults in particular at risk of suffering from medical conditions such as heat stroke.

Relying on historical data, the researchers used climate models to estimate future temperatures.

They said their conclusions highlighted the need to take measures now to avert a future public health crisis.

Measures to mitigate the effects of hot weather can include opening cooling centres and painting rooftops white to reflect light and keep homes cool. 

Thomson Reuters Foundation