Mitigating Aerosol Emissions Can Effectively Offset Climate Warming Impacts on Snowmelt

Northeast China is among the most polluted snow-covered regions globally due to substantial anthropogenic black carbon (BC) emissions. BC particles, upon deposition, darken the snowpack and subsequently accelerate snowmelt and disrupt spring water resource availability. While the impact of BC in snow (BCS) on snowmelt is widely recognized, its competitive effect relative to climate warming has been less studied, a critical knowledge gap given Northeast China's heavy reliance on snowmelt for agricultural and residential water use. This study, utilizing comprehensive field measurements across Northeast China, reveals alarmingly high BCS concentrations with a mean of 1100 ± 810 ng g^-1, 17 times greater than the global average. These high BCS levels contribute to 72% (0.82 cm d^-1) of accelerated snowmelt rates (ASR), surpassing the effects of climate warming (28%, 0.32 cm d^-1). Importantly, the observation-constrained CMIP6 projections under the SSP245 scenario indicate an 82% reduction in BCS by 2080-2100. This decline could offset 40% of the projected ASR increase by future warming, slowing the total ASR of 2080-2100 to 71% above that of 2000-2020. In contrast, the offset effect (3.6%-15%) is less pronounced in other regions of the Northern Hemisphere, highlighting the unique effectiveness of clean air policy implementation across Northeast China for mitigating snowmelt acceleration.