The city is no stranger to flooding. Even after a moderate downpour, a movie theater that Sugata Hazra favored as a young man would fill up with water. Dr. Hazra, now an oceanographer at Jadavpur University, remembers having to lift his feet in the middle of a movie. These days, even though many drains have been cleaned, low-lying parts of the city still get inundated. Traffic grinds to a halt.

The risk of flooding has increased, as extreme rainfall events have become more common. One study found that Kolkata is receiving many more heavy rainfall days than before.

One of Dr. Hazra’s doctoral students, Amit Ghosh, drilled down further. He found that between 1955 and 2015, the city recorded three times as many cloudburst days, when it rained more than 100 millimeters a day, as compared to the first half of the 20th century. These heavy rainfall events are disastrous for an already flood-prone city, where nearly a third of the population lives in slums, or worse, on the sidewalks under the open sky.

According to the Organization for Economic Cooperation and Development, if the current trajectory of greenhouse gas emissions continues, by 2070 Kolkata is projected to have more people exposed to coastal flooding than any city in the world.

Among cities facing growing flood-damage losses between now and 2050, Kolkata is projected to be among the top three.

“This is what we say to God: ‘If a storm comes, kill us and our children all at once, so no one will be left to suffer,” said Malati Mandal, a 30-year-old homeless mother of four. She lived on a sidewalk along Rashbehari Avenue, a 10-minute walk from my childhood apartment.