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The causes of catastrophic rainfall in Pakistan

Ali Hyder Junejo / Wikimedia CommonsCity covered by water in PakistanAli Hyder Junejo / Wikimedia Commons

Pakistan suffered the worst flooding in its history this year, with a third of the country affected, approximately 1,500 deaths, and 33 million people left homeless. The cause: a combination of climate and environmental factors. The catastrophe began with severe heat waves in April and May, when temperatures exceeded 40 degrees Celsius (ºC), reaching as high as 51 ºC in the city of Jacobabad. The intense heat exacerbated glacial melting in mountains in the north of the country, increasing the amount of water in the rivers that wind their way through the cities. These heat waves coincided with an intense low air pressure system in the Arabian Sea, which brought heavy rainfall to the country’s coastal cities in June. As a result of these weather phenomena, rainfall in Pakistan was three times higher than the average—in the south of the country, it was five times higher. Some one million homes, 5,000 kilometers of roads, and 240 bridges were destroyed, while 700,000 livestock animals were lost. In addition to the deaths and the economic and social impacts, the rains also pose a threat to the Mohenjo-daro ruins, a 4,500-year-old archaeological site and one of the best-preserved urban settlements in South Asia. Located on the right bank of the Indus River in the province of Sindh in southern Pakistan, Mohenjo-daro, meaning “Mound of the Dead,” was declared a world heritage site by UNESCO in 1980 (Nature, September 2).