Air pollution from early 20th Century European industry reshaped rainfall patterns across Asia’s summer monsoon, according to new international study involving Dr Massimo Bollasina in the School of GeoSciences Hang Dong, Chiang Mai, Thailand. Credit: zoutedrop/Flickr, CC-BY 2.0 Published in Atmospheric Chemistry and Physics, the study identifies rising European sulphate aerosol emissions as a key driver of multi-decadal monsoon shifts, including wetter conditions over South Asia and a southward displacement of East Asian rain belts.While most previous studies have focused on more recent decades, this research sheds light on an overlooked historical period, revealing how early industrial pollution had far-reaching impacts on regional climate. Pollution’s far-reaching climate effects Using historical emissions data, sophisticated climate models and detailed atmospheric circulation analysis, the team found that European aerosols emissions triggered large-scale changes in winds and atmospheric circulation stretching across Eurasia in the early 20th Century. These circulation shifts altered how moisture was transported into Asia, ultimately changing where and how much rain fell during the monsoon season. The results closely match historical observations of monsoon rainfall, providing strong evidence that pollution produced thousands of kilometers away played a major role in shaping Asian climate variability during that period. Why it matters today The Asian summer monsoon is one of the world’s most important climate systems. As well as being a vital source of water for over 60% of the world’s population it influences agriculture and flood risk for billions of people. This research reveals how emissions from outside Asia affected monsoon behaviour in the past and highlights the global reach of human-made air pollution and the complex links between regional emissions and the impacts in distant climates.The findings are particularly relevant as sulphur dioxide emissions in Europe continue to decline. Understanding how past aerosol changes altered atmospheric circulation will help scientists improve projections of future monsoon rainfall under evolving air-quality and global climate policies. As European SO₂ emissions continue to decline, this study sheds light upon a possible ongoing and future pathway that could significantly influence how the monsoon responds to changes in Asian aerosols. Rainfall changes driven by processes in distant regions may strongly shape, if not partially offset, the effects of local emission changes. Together, these findings illustrate the complex interplay between local and remote aerosols in driving significant changes in regional hydroclimate. Dr Massimo Bollasina School of GeoSciences | University of Edinburgh Related links Find out more about the teams’ methods and findings in the full paper:Sun, W., Bollasina, M. A., Colfescu, I., Wu, G., and Liu, Y.: European sulphate aerosols were a key driver of the early twentieth-century intensification of the Asian summer monsoon, Atmos. Chem. Phys., 26, 2027–2039, https://doi.org/10.5194/acp-26-2027-2026, 2026.View Dr Massimo Bollasina’s Research Explorer Profile Publication date 05 Mar, 2026
