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Under pressure: How climate change is impacting Indian cities
Summary
While New Delhi has been in the news for its pollution levels, no big Indian city is safe from the impacts of climate change, ranging from heatwaves to cyclones
New Delhi and the National Capital Region (NCR) is beset by problems, with the unbearable amounts of atmospheric pollution being the most acute. But the crisis of livability that the city faces isn’t just confined to this. There’s the annual heatwaves, the severe monsoon flooding, the horribly polluted Yamuna, and a brewing groundwater crisis. New Delhi isn’t a pleasant place to live in—to put it mildly—for much of the year.
In some ways, however, Delhi is a microcosm of the threats facing India as a whole. As many studies have pointed out over the years, India faces multiple imminent threats due to the climate crisis. Heatwaves, supercharged storms, cloudbursts, drought, melting Himalayan glaciers, a falling water table, drying rivers, increasing aridity, sea level rise. There isn’t a climate impact that India isn’t already suffering from. And with every passing year, the magnitude of these impacts is only going to get more acute.
Urban Heat: Delhi, Mumbai, Kolkata, Bengaluru
This places additional pressures on cities, especially since India is one of the fastest urbanizing countries in the world. According to the United Nations World Urbanization Prospects report from a few years ago, the number of Indians living is cities is expected to grow to 871 million by 2050. In the next six years, Ahmedabad and Hyderabad are set to join Delhi, Mumbai, Kolkata, Chennai and Bengaluru as cities with populations of over 10 million.
While this massive rise in urban migration raises the spectre of basic infrastructure-related problems, what may actually be of greater worry is heat stress. Cities typically are hotter because of the extensive heat island effect, and good urban planning—which can alleviate some of the problems—is sorely lacking in India anyway.
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A 2019 study titled Cities, Climate Change And Chronic Heat Exposure—found that Indian cities are a magnet for the most lethal form of heat: humid heat. Extreme high temperatures plus high humidity is a lethal cocktail which the human body just cannot stand. Measured as wet-bulb globe temperature (WBGT), anything above 30 degrees Celsius (while accounting for temperature, humidity, wind speed, solar radiation and sun angle), is lethal.
The study found that Delhi, Kolkata and Mumbai are already on the threshold of this limit. These three cities were classed as “Very Hot (Danger)", while a fourth city, Bengaluru, fell into the “Warm (Caution)" range. The worry is that as global temperatures continue to soar—2024 is on track to becoming the hottest year ever recorded, with an average heating of over 1.5 degrees Celsius since pre-industrial times—Indian heatwaves will get stronger and last longer. These will be felt even more intensely in cities.
Sea level rise and extreme storms: Mumbai, Kolkata, Chennai
Although our understanding of climate change impacts is formed purely by what we experience on land, the real story of global heating lies in the ocean. According to the World Meteorological Organization’s 2024 State Of The Climate report that was released last month, over the past fifty years, 90% of the extra heat trapped by excessive greenhouse gases (GHGs) in the atmosphere has been absorbed by the ocean. Since 1960, the ocean has been heating up, and this process has only accelerated in the past 20 years. From -300 zettajoules (ZT) in 1960 to 133ZT in 2023 is a massive jump.
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What is the effect of this overheated ocean? It’s causing longer and more severe marine heatwaves that bleaches and kills coral reefs, which sustain 25% of the global ocean ecosystem. This, along with increased ocean acidification will put a greater strain on seafood catch. But for human beings, the biggest effect of excess ocean heats is that Indian Ocean cyclones are becoming stronger every year.
Cyclones get supercharged by ocean heat, and due to marine heatwave conditions in the Bay of Bengal and the Arabian Sea, cyclones are growing both in both frequency and intensity. And megacities like Kolkata, Chennai and Mumbai lie in their path. The recent Cyclone Fengal may have missed Chennai by a whisker when it made landfall on 30 November, but it was the neighbouring Puducherry that faced the brunt. As of the time of writing, some 19 people had lost their lives in India and Sri Lanka, while Puducherry experienced its heaviest rainfall in 24 hours in 30 years. When Cyclone Dana made landfall in Odisha in late October, Kolkata was paralyzed with flooding. In each case—the most infamous being that of Cyclone Amphan in 2020—the storms became intensely strong in just a few hours because of high sea surface temperatures.
Connected to this annual hazard is the fact that with the gradual collapse of the Arctic permafrost and summer sea ice, along with rapidly melting Greenland and Antarctic ice sheets, global sea levels are rising in an alarming manner. Since 1993, satellites have been monitoring this rise, and in the past 30 years, global sea level has risen by over 110mm, and rose twice as fast in the past decade than it had in the first decade. In certain coastal regions, like around India, the rate of sea level rise is higher than the global rate.
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Not only does this spell trouble for coastal cities in the long term, even in the short term, higher sea levels can spell disaster when cyclones make landfall. Whenever the latter happens, you get a storm surge, where the force of the storm carries sea water inland in huge waves. During Cyclone Amphan, there was a storm surge of about 14 feet. It was the Sunderbans mangroves that prevented the storm surge of being even bigger. If the time a cyclone makes landfall coincides with high tide and higher sea levels, storm surges would be higher and lead to greater flooding. As cities like Mumbai, Kolkata and Chennai systematically destroy their mangroves and wetlands, they are increasingly without defenses for the climate change future.
So, while Delhi has been in the news recently due to its unmanageable pollution levels, there’s hardly any city in the country that isn’t facing environmental or climate-related threats of some kind or the other. And as India continues to urbanise at a rapid pace, the pressure is going to only increase.
