Desk Report
Publish: 05 Oct 2021, 08:58 pm
Dhaka || Photo: Collected
Rapid population growth and
global warming are increasing exposure to extreme heat in cities, aggravating
health problems and making moving to urban areas less beneficial for the
world's poor, according to a study released Monday.
The rise is affecting nearly
a quarter of the world's population, said the report published in the
"Proceedings of the National Academy of Sciences."
In recent decades, hundreds
of millions of people have moved from rural areas to cities where temperatures
are generally higher because of surfaces such as asphalt which traps heat and a
lack of vegetation.
Scientists studied the
maximum daily heat and humidity in more than 13,000 cities from 1983 to 2016.
Using the so-called
"wet-bulb globe temperature" scale, a measure that takes into account
heat and humidity, they defined extreme heat as 30 degrees Celsius (86 degrees
Fahrenheit).
The researchers then
compared weather data with statistics on the cities' population over the same
33-year period.
They calculated the number
of days of extreme heat in a particular year by the population of the city that
year to come up with a definition called person-days.
The authors found that the
number of person-days in which city dwellers were exposed went from 40 billion
per year in 1983 to 119 billion in 2016.
Cascade Tuholske at Columbia
University's Earth Institute, a lead author of the study, said the rise
"increases morbidity and mortality."
"It impacts people's
ability to work, and results in lower economic output. It exacerbates
pre-existing health conditions," he said in a statement.
Population growth accounted
for two-thirds of the exposure spike, with actual warming temperatures
contributing a third, although proportions varied from city to city, they
wrote.
Bangladesh's capital Dhaka
was the worst-affected city, seeing an increase of 575 million person-days of
extreme heat over the study period.
That was largely
attributable to its population soaring from around four million in 1983 to
around 22 million today.
Other big cities to show
similar trends were Shanghai, Guangzhou, Yangon, Dubai, Hanoi and Khartoum as
well as various cities in Pakistan, India and the Arabian Peninsula.
Major cities that saw around
half of their exposure causing by a warming climate included Baghdad, Cairo,
Kuwait City, Lagos, Kolkata and Mumbai.
The authors said the
patterns they found in Africa and South Asia, "may crucially limit the
urban poor's ability to realize the economic gains associated with
urbanization."
They added that "sufficient
investment, humanitarian intervention, and government support" would be
needed to counteract the negative impact.
In the United States, some
forty major cities saw exposure grow "rapidly," mainly in the Gulf
Coast states of Texas, Louisiana, Mississippi, Alabama, and Florida.
The study was carried out by
researchers at New York's Columbia, University of Minnesota Twin Cities, the
University of Arizona at Tuscon and the University of California, Santa
Barbara. (AFP)
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Topic : Dhaka World's Worst City
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