Heat stress escalates in cities under global warming


Heatwaves are intensifying in cities due to the double whammy of the urban heat island effect and global warming, according to a new study.

The study’s authors used computer models to simulate with unprecedented detail the temperature changes through the mid-21st century in Belgian cities. They found that heatwaves become hotter, longer and more frequent because of greenhouse gas emissions, and that temperature above the heat stress alarm level increases by a factor of between 1.4 and 15 by the middle of this century.

“The trends are very harmful to an increasing share of people living in the cities, since hot temperatures lead to excessive mortalities, hospital admissions, energy usage and economic loss, which are exacerbated by the urban heat island,” said Hendrik Wouters, of Belgium’s Katholieke Universiteit Leuven and Ghent University.

More deaths from future heat waves could make heat waves the most deadly type of natural disaster in the near future, he added. Wouters is the lead author of the study which appears in Geophysical Research Letters, a publication of the American Geophysical Union.

The urban heat island effect is caused largely by solar energy being converted into heat by stone and concrete in buildings and pavement. At the same time, cities lack cooling provided by vegetation and water, and more heat is generated by human activities and technology.

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