Marine cloud brightening, a form of solar radiation modification designed to reflect more sunlight from low-lying ocean clouds, could substantially reduce some of the world’s future drought risks while intensifying drought in other regions, according to a new climate-modeling study. The research, led by Long Cao of Zhejiang University and Jiu Jiang of Xinjiang University, finds that the consequences of deploying the technology would be neither uniformly beneficial nor globally predictable. Instead, the intervention could reorganize terrestrial drought patterns across continents, easing water stress in some of the world’s most vulnerable regions while worsening conditions in parts of eastern South America and Eurasia.
The study uses the Community Earth System Model version 2, or CESM2, to simulate how global land drought responds to marine cloud brightening under the intermediate-emissions pathway SSP2-4.5. The researchers conducted multi-member ensemble experiments extending to the end of the century and compared two future climates: one following the SSP2-4.5 pathway alone and another in which marine cloud brightening was introduced. In the simulations, sea-salt aerosols were injected into three subtropical ocean regions covering roughly 12 percent of the global ocean surface. These particles act as cloud condensation nuclei, increasing the number of cloud droplets and making marine clouds brighter and more reflective. By scattering additional incoming solar radiation back into space, the intervention lowers the energy reaching Earth’s surface and can reduce global temperatures.
The model projects that marine cloud brightening could produce a global mean cooling of approximately 0.9 degrees Celsius by the final decade of the 21st century compared with the SSP2-4.5 baseline. That cooling would not simply counteract rising temperatures. It would also alter the atmospheric demand for water, a factor that strongly influences drought. Warmer air can hold more water vapor, increasing potential evapotranspiration—the amount of water that could evaporate from land and be released by plants under available moisture conditions. As temperatures fall, potential evapotranspiration generally declines. In the model experiments, this suppression of atmospheric water demand becomes the principal reason that many regions experience reduced drought pressure under marine cloud brightening.
The researchers assessed drought through several complementary characteristics rather than relying on a single index. Drought intensity describes the strength of moisture deficits, while drought severity reflects the accumulated effect of those deficits over time. Drought frequency measures how often drought conditions occur, and drought duration captures how long individual events persist. The study also examined drought occurrence and the area affected by drought. Together, these indicators reveal whether a region is experiencing fewer droughts, shorter events, weaker deficits, or a smaller overall footprint of drying. The scientists compared averages from 2091–2100 with a 2015–2024 baseline and evaluated whether simulated changes were statistically distinguishable using Welch’s t-test at the 95 percent confidence level.
At the global scale, the simulations indicate that marine cloud brightening would lessen the drying trend expected under SSP2-4.5. Global mean drought intensity, severity, frequency and affected area all decline in the intervention scenario. The result is especially notable because drought does not depend solely on rainfall. A region can become drier because precipitation decreases, because heat accelerates evaporation, or because both processes occur simultaneously. Marine cloud brightening appears to reduce one of the most important amplifiers of drought—heat-driven atmospheric moisture demand—even where precipitation responses are uneven. This means that a cooler climate can reduce drought stress without producing a uniform increase in rainfall everywhere.
The strongest benefits emerge across many tropical and subtropical land areas. The African Sahel, South Asia and Australia are among the regions where the intervention substantially mitigates, and in some cases more than offsets, the drought stress associated with greenhouse-gas warming in the SSP2-4.5 scenario. These regions already face high exposure to rainfall variability, heat extremes, agricultural water demand and ecosystem stress. A reduction in potential evapotranspiration could therefore have important consequences for soil moisture and plant water availability. However, the study does not imply that marine cloud brightening would eliminate drought in these areas. Rather, it suggests that the frequency, severity or persistence of drought may be lower than it would be without the intervention.
The same atmospheric and circulation changes that ease drought in one region can intensify it elsewhere. Parts of eastern South America and portions of Eurasia show more severe drought conditions relative to SSP2-4.5 in the simulations. Such regional contrasts arise because marine cloud brightening changes more than surface temperature. Altered radiation and cooling patterns can affect atmospheric circulation, moisture transport, cloud formation and precipitation across vast distances. The location of aerosol injection is therefore critical: cooling imposed over selected subtropical oceans can trigger responses in distant land regions through changes in winds, pressure patterns and ocean-atmosphere interactions. A strategy optimized to reduce drought in one vulnerable region could unintentionally shift climatic risks toward another.
This geographical unevenness presents a major challenge for the governance of solar radiation modification. Marine cloud brightening is sometimes portrayed as a potentially rapid way to offset global warming, but the new findings emphasize that a global average temperature target cannot capture the full distribution of climate impacts. The same intervention could reduce aggregate drought indicators while producing damaging local outcomes for communities, food systems or ecosystems in areas that receive less favorable precipitation and circulation responses. Decisions about deployment would consequently require regional climate assessments, agricultural and hydrological modeling, and long-term monitoring rather than relying solely on global temperature statistics.
The study also highlights the limits of treating modeled climate benefits as direct policy recommendations. CESM2 simulations can reveal physically plausible responses and help identify mechanisms, but they cannot reproduce every uncertainty surrounding aerosol behavior, cloud microphysics, precipitation feedbacks or the social consequences of drought. Marine cloud brightening would depend on the effectiveness, location and duration of aerosol release, as well as on how clouds respond in different marine environments. The researchers’ use of ensemble simulations and statistical testing strengthens the assessment of robust signals, yet areas marked by statistically insignificant changes remain important because uncertainty itself can complicate adaptation planning. Further experiments using multiple climate models, alternative deployment patterns and broader impact assessments will be needed before the risks can be fully understood.
By showing that marine cloud brightening could simultaneously relieve and worsen drought, the research adds urgency to the debate over regional climate intervention. Its central message is not that the technology offers a simple solution to climate change, but that any future deployment would produce a complex redistribution of environmental risks. Cooling the planet could reduce heat-driven drying across large areas, particularly in the tropics and subtropics, while circulation changes could intensify drought elsewhere. The findings provide a scientific basis for exploring regionally tailored adaptation strategies, but they also underline the need for international oversight, transparent modeling and careful consideration of communities beyond the intended target zones. As climate pressures intensify, the prospect of brightening ocean clouds may attract growing attention—but the study suggests that changing the planet’s radiative balance could make drought relief a matter of geography, trade-offs and global responsibility.
Subject of Research: Simulated global terrestrial drought response to regional marine cloud brightening.
Article Title: Simulated response of global terrestrial drought to regional deployment of marine cloud brightening.
Web References: https://doi.org/10.1007/s11430-025-1837-2
References: Jiang J, Fang Y, Cao L, Yu X. 2026. “Simulated response of global terrestrial drought to regional deployment of marine cloud brightening.” Science China Earth Sciences, 69(8): 2824–2838. DOI: 10.1007/s11430-025-1837-2.
Image Credits: © Science China Press
Keywords: marine cloud brightening, solar radiation modification, drought, climate change, CESM2, potential evapotranspiration, climate modeling, drought risk, aerosol injection, regional climate impacts
