Around 44 cities worldwide, are likely to face the worst levels of dangerous heat stress under global warming and could experience in future twice the average number of extreme hot days a year, new research has suggested.
The study has predicted increases in the frequency of deadly heat waves worldwide with six South Asian cities among the top ten facing the highest heat stress burden, a measure that combines the temperature, humidity and the population exposed to the heat.
The findings suggest that Calcutta, which experienced on average 16 days of extreme heat per year between 1979 and 2005, is likely to face 44 days of similar heat in the coming years or decades.
This doubling is projected to occur, when the average global temperature rises to 1.5°C above what it was in the late 19th century, or the pre-industrial era. Climate studies show that the average global temperature between 1986 and 2005 had already reached about 0.8°C above the pre-industrial level.
The research has also projected that over 350 million inhabitants of mega-cities across the world will experience intense heat waves in the coming decades, a four-fold increase compared to the global population exposed to such heat between the years 1979 and 2005.
“The higher the heat stress, the more the potential societal impacts,” said Tom Matthews, a climatologist at Liverpool John Moore University in the UK, who led the study collaborating with researchers in Ireland and the UK.