Summary

Situated at the southern edge of the Tibetan Plateau (TP), the Hindu-Kush-Himalayas-Gangetic (HKHG) region is under the clear and present danger of climate change. Flash-flood, landslide, and debris flow caused by extreme precipitation, as well as rapidly melting glaciers, threaten the water resources and livelihood of more than 1.2 billion people living in the region. Rapid industrialization and increased populations in recent decades have resulted in severe atmospheric and environmental pollution in the region. Because of its unique topography and dense population, the HKHG is not only a major source of pollution aerosol emissions, but also a major receptor of large quantities of natural dust aerosols transported from the deserts of West Asia and the Middle East during the premonsoon and early monsoon season (April–June). The dust aerosols, combined with local emissions of light-absorbing aerosols, that is, black carbon (BC), organic carbon (OC), and mineral dust, can (a) provide additional powerful heating to the atmosphere and (b) allow more sunlight to penetrate the snow layer by darkening the snow surface. Both effects will lead to accelerated melting of snowpack and glaciers in the HKHG region, amplifying the greenhouse warming effect. In addition, these light-absorbing aerosols can interact with monsoon winds and precipitation, affecting extreme precipitation events in the HKHG, as well as weather variability and climate change over the TP and the greater Asian monsoon region.