Urban heat exposure affects quarter of the world's population

A study published in the Swedish scientific journal PNAS has revealed that global incidents of extreme heat issues in urban areas has risen nearly 200% in 13,115 cities from 1983 to 2016, affecting 1.7 billion people or nearly 25% of the global population.

The study highlights the use of materials like concrete, glass and asphalt in cities as well as disappearing vegetation which has increased the levels of heat experienced by city dwellers, especially the urban poor. The worst affected city named in the study is Dhaka in Bangladesh, which experienced rapid growth between 1983 and 2016. During this time, Dhaka experienced an increase of 575 million "person-days" (cumulative exposure faced by the population over a year in one place) of extreme heat. Other cities that underwent rapid population growth include Shanghai and Guangzhou in China, Yangon in Myanmar, Bangkok in Thailand and Dubai in the United Arab Emirates.

Using infrared imagery, humidity and temperature readings as well as statistical models, the study authors also looked at the impact of 'global heating' vs urban heating as the Earth continues warming due to man-made climate change. Cities that had at least half of their heat exposure caused by global heating include Baghdad in Iraq, Cairo in Egypt and Mumbai in India. More cities also reported extreme heatwaves in the short three-decade period. Overall, scientists attributed two-thirds of the overall rise in exposure to increased urban populations and a third of it to global heating.

Increased urbanisation and population was the main driving force behind such events and would only worsen in the future if no action was taken, warned scientists. In addition to this, the impact of extreme heat on human life and health was detrimental, the study notes.

More studies from Brazil and Europe also note the devastating impact of heatwaves on the population and environment at large, with Scientists from the European Commission's Joint Research Centre and other institutions estimating that annual heatwave incidents will rise to 1.14% on average, costing Europeans millions of dollars.