Air pollution reductions caused by the COVID-19 lockdown open up a way to preserve the Himalayan snow cover

Abstract. The rapid melting of glaciers in the Hindu Kush Himalayas (HKH) during recent decades poses an alarming threat to water security for lager parts of Asia. If this melting persists, the entire Himalayan glaciers is estimated to disappear by end of 21st century. Here, we assess the influence of the spring 2020 COVID-19 lockdown on the HKH, demonstrating the potential benefits of a strict emission reduction roadmap. Chemistry-climate model simulations, supported by satellite and ground measurements, show that lower air pollution during lockdown led to a reduction in black carbon in snow (2–14 %) and thus in snow melting (10–40 %). This caused increases in snow cover (6–12 %) and mass (2–20 %) and a decrease in runoff (5–55 %) over the HKH and Tibetan Plateau, ultimately leading to an enhanced snow-water-equivalent (3.3–55 %). We emphasize the necessity for immediate anthropogenic pollution reductions to address the hydro-climatic threat to billions of people in South Asia.