On Sept. 23, the city of Kolkata in eastern India came to a standstill: The capital of West Bengal state received more than 12% of the city’s average annual rainfall in just 24 hours, some 247.5 millimeters (9.7 inches). The subsequent flooding claimed lives and caused extensive property damage. Scientists say climate change has made such extreme weather events in Kolkata more frequent, but the city’s stressed and aging drainage system exacerbated the impact, reports contributor Snigdhendu Bhattacharya for Mongabay India. Research shows that the Indian Ocean, including the Bay of Bengal, which borders the coastline of West Bengal, is warming faster than the global average. Under such conditions, a low-pressure area over the bay draws in more moisture from the oceans, leading to more intense weather events, said Mahesh Palawat of Skymet Weather, a private weather forecast service. Kolkata itself has the highest recorded urban warming among global megacities over the past seven decades: about 2.6° Celsius (4.7° Fahrenheit) between 1950 and 2018. Warm air can hold more moisture, so “every degree rise leads to a rise in moisture content by 7%,” said Kartiki Negi of Climate Trends, a New Delhi-based research and advocacy group. More atmospheric moisture can also lead to more intense weather activities, he added. Kolkata’s climate action report notes the city is facing increasing threats from heat waves, flooding, sea level rise and more intense cyclones. Urbanization, too, has taken a toll. New townships and roadways have been built on natural drainage paths of rivers and swamps. What were…This article was originally published on Mongabay