Kolkata, formerly Calcutta, is the capital of the Indian state of West Bengal. Due to climate change however, in the twenty-first century Kolkata is also the city with the most people at risk of sea level rise. As the climate changes, with sea level rise and a delayed but more intense monsoon, severe flooding is increasingly bringing the city to a standstill for several days at a time. The wider Indian Bengal Delta is one of the most vulnerable in the world as a result of climate change. The Intergovernmental Panel on Climate Change’s Fifth Assessment Report estimates 1 metre as the upper end of the ‘likely range’. Kolkata is particularly vulnerable to the climate change-induced heat island effect, where cities are hotter than their surrounding areas. Kolkata may represent one of the most extreme examples, but cities around the world will be profoundly affected by a changing climate, causing massive disruption, economic costs, and ill-health.