New Delhi recorded the highest number of days when the temperature was over 35°C out of 20 capital cities analysed by London-based International Institute for Environment and Development (IIED), an independent policy and action research organisation working primarily in the global South.
New Delhi saw 4,222 days reaching that threshold over a 30-year period. During the past decade alone, 44% of days in the city reached 35°C – a significantly higher percentage than the previous two decades (37% in 2004-2013; 35% in 1994-2003).
The world’s 20 biggest capital cities covered in the analysis are:
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Asia
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Bangkok, Beijing, Dhaka, Jakarta, Kuala Lumpur, Manila, New Delhi, Seoul, Tokyo
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Middle East
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Cairo, Tehran
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Africa
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Kinshasa, Luanda
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Europe
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London, Paris, Moscow.
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South America
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Buenos Aires, Bogota, Lima, Mexico City
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These 20 cities, home to over 300m people, experienced a 52% increase in the number of days reaching 35°C over the past three decades, according to the analysis by IIED.
Cumulatively, there were 16,586 days where the temperature hit at least 35°C during the 30-year period. However, with each decade, the number has been steadily rising:
- 1994-2003: 4,755 days
- 2004-2013: 5,343 days
- 2014-2023: 6,488 days
There’s growing consensus that heat waves should be officially categorised as disasters. This research highlights the urgent need for policymakers to do more to help communities adapt to the new reality of these hotter temperatures, says IIED.
IIED senior researcher Tucker Landesman said, “Climate change is not just a future threat – it’s already happening and getting worse.
“In just one generation, there’s been an alarming increase in the number of days of extreme heat affecting some of the world’s biggest capital cities - made worse by the urban heat island effect.
“Millions more people are experiencing heat stress as temperatures reach dangerously high levels in some cities, which is having a profound impact on people’s health.”
What needs to be done
He added, “For many cities, it’s not a lack of knowledge or capacity or resources that’s preventing large-scale action to address climate change, rather it’s a lack of political will and governing tools.
“To make change happen, there needs to be strategic coordination between health, finance, environment and transport policy experts, along with civil society groups and frontline communities. Without a properly resourced response to the climate crisis, millions of people will continue to suffer the worst effects of climate change.”
To learn more about the analysis, please click here.