Monsoon rainfall supports farming and water supplies for billions of people. Understanding how regional rainfall responds after peak warming is essential for assessing water availability over the coming centuries.

A new study led by researchers from the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS) examines monsoon rainfall through 2300. Published in Journal of Climate, it shows that little change in average rainfall across the world’s land monsoon regions can mask substantial regional shifts. The study also explains partial rainfall reversals in South Asia and North America and identifies a key source of uncertainty in African monsoon projections.

Using long-term simulations from 16 Coupled Model Intercomparison Project (CMIP) models, the team examined the extended low-emission pathways RCP2.6 (CMIP5) and SSP1-2.6 (CMIP6). Under both pathways, radiative forcing and global temperatures decline after 2100. The team first compared model families (groups developed from a common base model) and generations (groups participating in the same round of CMIP). Rainfall change patterns were more similar within generations, but not significantly more similar within families. The team then examined regional changes and mechanisms.

By the late twenty-third century (2250–2299), South Asian monsoon rainfall declines relative to the late twenty-first century (2050–2099), offsetting about 29% of the earlier projected wetting relative to the historical climate (1950–1999). North American monsoon rainfall increases instead, recovering about 39% of the earlier projected drying. Different processes drive these partial reversals. In South Asia, cooling reduces atmospheric moisture, weakening its contribution to monsoon rainfall. In North America, changes in atmospheric circulation favor more rainfall and outweigh the opposing effect of reduced atmospheric moisture.

Compared with the broadly consistent projections for South Asia and North America, Africa shows much greater inter-model spread. For changes between the late twenty-first and late twenty-third centuries, CMIP5 generally projects wetter northern and drier southern monsoon regions, while CMIP6 tends toward the reverse. This north–south pattern explains about 56% of the variance in projected African monsoon rainfall changes across models. The team linked these contrasting projections to differences in the north–south Atlantic sea surface temperature contrast. Changes in this contrast shift the tropical rain belt, altering moisture transport and upward air motion over Africa. Therefore, improving the simulation of these processes is important for reducing uncertainty in long-term African monsoon projections.

The findings show how distinct regional processes shape monsoon rainfall after peak warming. Accounting for changes in atmospheric moisture, circulation and ocean temperature patterns can help inform long-term water-resource planning and climate adaptation.

Paper info：

Ren, K., T. Zhou, W. Zhang, Z. Ren, J. Jiang, and X. Chen, 2026: Long-Term Extended Projection of Global Land Monsoon Precipitation Beyond 2100 under a Low-Emission Scenario. Journal of Climate, 39, 4989–5003. https://doi.org/10.1175/JCLI-D-25-0677.1.