About 25% of the world’s population exposed to deadly city heat
About 25% of the world’s population is exposed to deadly city heat. The new report found exposure to deadly urban heat has tripled since the 1980s.
The urban heat now affects nearly a quarter of the world’s population. The new research published in the journal PNAS and a postdoctoral researcher at Columbia University’s Earth Institute revealed.
Scientists have the worrying development down to the combination of rising temperatures and urbanization.
They warned of potential deadly impact if the current trends in global heating and emissions continue unabated.
Hundreds of millions of people have moved from rural areas to urban areas which are now home to more than half the world’s population.
The urban buildings are made of concrete and asphalt surfaces which traps and concentrate more heat. With little vegetation in urban areas, temperatures are generally higher.
“This has broad effects,” said Cascade Tuholske, the lead author of the study. “It increases morbidity and mortality. It impacts people’s ability to work and results in lower economic output. It exacerbates pre-existing health conditions.”
The research used infrared satellite imagery and maximum daily heat and humidity readings from more than 13,000 cities from 1983 to 2016 to determine the number of people exposed to the days a year that exceeded 30C (86F) on the wet-bulb globe temperature scale (which takes into account the multiplier effect of high humidity) in an area.
The scientists matched the findings with the cities’ populations over the same period.
The study found that the number of person-days (the cumulative population exposed to cumulative heat in a given year for a particular place) rose from 40bn a year in 1983 to 119bn in 2016, representing a threefold increase.
In 2016, 1.7 billion people were subjected to extreme heat conditions on multiple days.
Although it varied between cities and regions, scientists attributed two-thirds of the overall rise in exposure to increased urban populations and a third of it to global heating.
The worst affected city was Dhaka. Between 1983 and 2016, during which time the city’s population rose dramatically, Bangladesh’s capital experienced an increase of 575 million person-days 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.
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.
Of the cities studied, 17% experienced an additional month of extreme-heat days during the period, which spanned just over three decades.
Cascade Tuholske said: “A lot of these cities show the pattern of how human civilization has evolved over the past 15,000 years. The Nile, the Tigris-Euphrates, the Ganges … there is a pattern to the places where we wanted to be. Now, those areas may become uninhabitable. Are people really going to want to live there?”
Source, The Guardian