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

The rapid melting of glaciers in the Hindu Kush Himalayas (HKH) during recent decades poses an alarming threat to water security for larger parts of Asia. If this melting persists, the entirety of the Himalayan glaciers are estimated to disappear by end of the 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 levels of gas and aerosol pollution during lockdown led to changes in meteorology and to a reduction in black carbon in snow (2 %-14 %) and thus a reduction in snowmelt (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-equivalent water (2 %-55 %). We emphasize the necessity for immediate anthropogenic pollution reductions to address the hydro-climatic threat to billions of people in southern Asia.