El Nino – Study Examines Cloud Brightening to Reduce Climate Disruption
El Nino – A new study has examined whether deliberately brightening clouds above the Pacific Ocean could weaken an emerging El Nino and reduce some of the extreme weather associated with the climate pattern. Researchers say the approach remains theoretical, carries major practical and environmental questions, and is not a substitute for cutting greenhouse-gas emissions.
Research focuses on targeted climate intervention
The study, published in Science Advances, used computer simulations to test whether marine cloud brightening could cool a key area of the equatorial Pacific during the early development of El Nino conditions. Unlike broader geoengineering proposals designed to lower global temperatures, the research looked at a more limited intervention aimed at influencing a specific climate cycle.
El Nino develops when sea surface temperatures rise across parts of the eastern tropical Pacific. Its effects can extend far beyond the ocean, often bringing drought and heat to some regions while increasing rainfall and flood risks in others. Australia can face drier conditions, East Africa may experience wetter seasons, and global average temperatures can also rise during strong events.
Lessons drawn from Australian bushfire smoke
The researchers were partly inspired by the 2019-20 Australian bushfires, commonly known as the Black Summer fires. Smoke particles from those fires entered the atmosphere and altered cloud properties, making some clouds brighter and allowing them to reflect more sunlight back into space.
Earlier research suggested that this natural process contributed to the development of a prolonged La Nina phase, the cooler counterpart to El Nino within the El Nino-Southern Oscillation system. The new study explored whether a similar cooling effect could be produced intentionally through marine cloud brightening.
Jessica Wan, a postdoctoral researcher at the University of Chicago and the study’s lead author, said shorter and more targeted interventions could eventually become part of a broader climate response strategy. However, she stressed that the value of any such action would depend on whether it reduced harmful effects over land, rather than simply lowering temperatures in one ocean region.
Simulations tested two major El Nino events
The team used a climate forecasting model to assess how cloud brightening might have affected the powerful El Nino events of 1997-98 and 2015-16. Their scenario involved releasing sea salt particles into low-lying clouds over a large section of the equatorial Pacific.
In theory, specially equipped ships could spray fine seawater droplets into the atmosphere. The salt particles could help clouds reflect more incoming solar energy, potentially cooling the ocean surface below.
The simulations found that the approach was most effective when begun early, around June, and continued until the following February. Under those conditions, the model showed that many temperature and rainfall changes linked to El Nino could be reduced or reversed.
Technology and regional risks remain unresolved
The proposal faces significant engineering barriers. Marine cloud brightening equipment is still being developed, and current nozzles cannot produce the volume needed for an intervention of this scale. The study estimated that about 2,400 ships could be required if the method were ever deployed widely.
Researchers also warned that the results would not be uniformly positive across all regions. The models identified possible unintended warming in parts of Europe and Asia. Some places may also benefit from El Nino-related weather patterns, meaning suppressing the event could create new challenges elsewhere.
Debate continues over geoengineering research
The study did not examine the long-term consequences of repeatedly using cloud brightening to weaken El Nino events. That remains a major gap, especially as scientists debate whether climate intervention technologies could create new risks or reduce pressure on governments and industries to cut emissions.
Wan said research should continue alongside stronger action to reduce carbon pollution. She argued that warming already built into the climate system means scientists need to understand whether carefully governed interventions could help limit the most damaging impacts while long-term climate solutions are pursued.