Future Biomass Burning in the Indochina Peninsula as a Major Barrier to Air Quality Improvement in Southwestern China

Abstract During the dry season (February−April), open biomass burning (OBB) in the Indochina Peninsula (ICP) substantially affects air quality and public health both locally and in downwind China, yet little is known about its future changes under a warming climate. Here we show that OBB‐PM 2.5 transport is a key factor for future air quality attainment in southwestern China. From 2015 to 2017, dry season OBB in the ICP contributed 32.6 μg m −3 of PM 2.5 locally and 6.9 μg m −3 in southwestern China. By 2058−2060, these contributions are projected to increase by 39%–45.2 μg m −3 in the ICP and by 58% to 11.0 μg m −3 in southwestern China, causing more than half of the southwestern provinces to miss the World Health Organization (WHO) Interim Target‐3 (15 μg m −3 ) that they would otherwise have achieved. This increase is primarily driven by enhanced OBB emissions, while climate change further shapes a surface tripole pattern—producing southeast‐low and northwest‐high concentrations over the ICP with slight increases in the South China–Taiwan region—and modifies vertical transport from the ICP to southwestern China by weakening it in the lower free troposphere but strengthening it within the boundary layer. Future short‐term exposure to OBB‐related PM 2.5 is projected to cause 29,500 premature deaths (∼37% increase) in the ICP and 12,300 (∼55% increase) in southwestern China. These findings highlight the growing threat of OBB pollution transport and emphasize that controlling OBB in the ICP is crucial for improving air quality in China.