Brown Carbon From Biomass Burning Reinforces the Himalayas and Tibetan Plateau Warming

The Himalayas and Tibetan Plateau (the HTP), referred to as “the third pole” with an excessive warming rate, exerts strong impacts on the global environment. As one of warming contributors, atmospheric brown carbon (BrC) remains limited scientific understanding in the HTP due to a scarcity of observations. In this study, we present a study of the light-absorbing properties of methanol-soluble brown carbon (MeS-BrC) and water-soluble brown carbon (WS-BrC) during 2018–2021. Highly spatiotemporal variations of BrC light absorptions were observed. In the HTP marginal area, elevated BrC absorption coefficients at 365 nm (b_abs,365) and levoglucosan concentrations were obtained, and MeS-BrC exhibits approximately 1.3–1.8 times higher absorption compared to WS-BrC. We determined that BrC light absorptions was largely attributed to biomass burning (29%–35%). BrC can act as a potent warming agent in the HTP marginal area, with high direct solar absorption (25%–47% relative to black carbon).