Rise in heatwaves puts pressure on city planning

Catarina Chagas in SciDev.net: Cities around the world are likely to suffer more heatwaves in the future, a study has found, leading to greater need for planning regulation and urban cooling. The study found a significant increase between 1973 and 2012 in the number of heatwaves affecting the 217 urban areas around the world it examined.

It also found that almost two-thirds of cities saw significant rises in ‘extreme hot nights’, which are as warm as the daily minimum temperature. Such nights are dangerous as they mean people have no respite from hot days.

As climate change progresses and cities become denser, these problems could be exacerbated, say the authors of the study, which was published on 29 January in Environmental Research Letters.

Vimal Mishra, the lead author of the study and an engineer at the Indian Institute of Technology, Gandhinagar, says it is particularly important to understand changes to urban climate, as around 70 per cent of the world’s population are forecast to be living in cities by 2050.

Large cities generate their own microclimates, called urban heat islands. This effect means temperatures in urban areas are higher than those in surrounding rural areas, explains Diane Archer, a researcher at policy research organisation the International Institute for Environment and Development. “This is because of the concentration of buildings trapping more heat during the day and releasing it more slowly at night than natural ground cover like vegetation,” she says....

Gokuldham in Mumbai, shot by Gaggarkartik, Wikimedia Commons, public domain