The global monsoon system is pivotal in shaping ecosystems, agriculture, and economies across vast swathes of the world. Amid climate change, understanding the evolution of land water availability—gauged as precipitation minus evaporation (P–E)—is crucial for ensuring sustainable development and environmental protection in monsoon-affected regions.

While prior research, including the Intergovernmental Panel on Climate Change's Sixth Assessment Report (IPCC AR6), has largely centered on trends driven by greenhouse gases (GHGs), a new study from the Institute of Atmospheric Physics of the Chinese Academy of Sciences highlights that aerosol reduction plays an equally important role in driving future P–E changes across global monsoon regions.

Recently published in Science Bulletin, the study analyzes P–E changes from 1951 to 2100, with future projections based on the mid-range emissions scenario SSP2-4.5. It finds that both rising GHG concentrations and shifts in the core areas of anthropogenic aerosol (AA) emissions are key drivers of long-term trends and regional variations in P–E across global and regional monsoon zones.

The findings paint a complex picture for the future: Escalating GHG concentrations are projected to boost P–E in Asian–African monsoon regions while lowering it in American monsoon regions. In contrast, aerosol reductions will reverse the current widespread drying trend to future wetting, with their impact on Asian–African monsoon regions being comparable to that of GHG forcing. 

These diverse regional precipitation patterns stem from dynamic processes linked to atmospheric circulation shifts and aerosol–cloud interactions, as both rising GHG concentrations and declining AA emissions can enhance atmospheric moisture and strengthen thermodynamic processes.

"Many studies have underscored greenhouse gases' critical impact on the water cycle, but our work emphasizes that both carbon neutrality and clean air policies must be considered when tackling future water resource challenges—particularly in densely populated monsoon regions," said Dr. JIANG Jie, the study's first author.

This study provides critical insights for climate policy and water resource management, the researchers noted.