Hundred-year forecast warns of longer, hotter heatwaves

HEATWAVES are likely to become more severe, frequent and long lasting this century, scientists said yesterday.

Periods of scorching hot weather, as occurred in Europe last year, claim thousands of lives.

But a new climate-modelling study from the US predicts they will become even more common and extreme.

The results show higher levels of man-made greenhouse gases threaten to intensify unusual atmospheric circulation patterns already linked to heatwaves in North America and Europe.

As the patterns become more pronounced, severe heatwaves will hit the Mediterranean and southern and western US.

Other parts of France, Germany and the Balkans are expected to become more susceptible to heatwaves.

The study by climatologist Gerald Meehl and Claudia Tebaldi, from the National Centre for Atmospheric Research (NCAR) in Colorado, focused on Chicago and Paris.

An estimated 15,000 people died as a result of the heatwave in France last August. Chicago’s heatwave of July 1995 killed about 739.

“It’s the extreme weather and climate events that will have some of the most severe impacts on human society as the climate changes,” said Meehl.

Over the coming century, the number of heatwaves in Paris was expected to increase by 31% and in Chicago by 25%.

They would also be more intense. In the model, the worst three-day heatwaves showed a rise of more than 3C in minimum night-time temperatures in the Mediterranean region and western and southern US.

During the 1995 Chicago heatwave, the most severe health impact resulted from a lack of cooling relief several nights in a row, according to health experts.

Future heatwaves would also last longer, said the scientists.

Parisian heatwaves were expected to stretch from the present day range of 8.33 to 12.69 days to between 11.39 and 17.04 days in the coming decades.

For Chicago, heatwaves would expand from 5.39 to 8.85 to between 8.5 and 9.24 days.

The researchers wrote in the journal Science: “Areas already experiencing strong heatwaves (eg southwest, midwest and southeast US and the Mediterranean region) could experience even more intense heat waves in the future.

“But other areas (eg northwest US, France, Germany, and the Balkans) could see increases of heatwave intensity that could have more serious impacts because these areas are not currently as well adapted to heatwaves.”