Can the impact of a major El Nino be reduced by making some clouds over the ocean more reflective? A study published in July 2026 examined this question with a computer model. The study showed some possibilities, but it did not prove that doing this over a real ocean is safe, feasible or accepted. This subject matters for India because changes in the Pacific Ocean can also affect the weather of distant regions. Besides, an intervention that benefits one region can create risk for another.
What did the study do?
Research published in Science Advances on 8 July 2026 examined the possible effect of marine cloud brightening on El Nino. The researchers did not send a fleet of real ships into the ocean to change El Nino. They used historical contexts such as the major El Ninos of 1997-98 and 2015-16 in an Earth-system model and compared hypothetical interventions of different timing and duration. So its findings are model-based possibilities, not a report of successful deployment in the real world.
The research also referred to the particles released by the Australian bushfires of 2019-20 and the changes in clouds. According to earlier research, these changes may have contributed to a La Nina-like response. Treating this as a natural example obtained by chance, the model's understanding was tested. This does not mean that bushfires are beneficial or should be considered a way to fix the climate. Unplanned fires and controlled intervention are not the same kind of process either.
How can clouds become brighter?
The droplets of some low clouds over the ocean are affected by the microscopic particles present in the air. The marine cloud brightening proposal examines the possibility of sending more sunlight back towards space by changing the number and size distribution of droplets in such clouds. One proposed method uses very small particles of sea salt. This is a subject of scientific and technical investigation; the mere presence of salt in the sea does not automatically make any additional intervention safe.
The target here is to change the reflectivity of some marine clouds. It should not be equated with rain-inducing cloud seeding. It is also different from the proposal to place reflective particles in the stratosphere. Both can be placed within the broader debate on solar radiation modification, but the altitude, process and potential effects differ. The response of clouds depends on local conditions, pre-existing particles and weather. Assuming the same result in every cloud would be wrong.
What is the connection with El Nino?
El Nino is not merely an isolated patch of warm water in the Pacific Ocean. It is part of a system of mutual influence between the ocean and the atmosphere. Under normal conditions, the trade winds play a role in keeping warm surface water towards the west of the equatorial Pacific. During the development of El Nino, changes in the winds, the sea-surface temperature and the upwelling of cold water can reinforce one another.
This mutual influence is explained by the Bjerknes feedback. The question in the research was whether brightening selected clouds in the south-eastern Pacific could cool the ocean surface and alter this air-sea relationship. In the model, some interventions weakened the development of El Nino. The results could not be explained by local cooling alone; the dynamic response of the ocean and atmosphere was also important. This should not be seen as switching El Nino off with a simple switch.
Why did timing and duration turn out to matter?
In the model, interventions that started relatively early and ran longer were more effective in some situations. An intervention made late, near the peak of El Nino, could yield a smaller result. But this does not produce advice to start an intervention immediately. First there must be an estimate of whether an El Nino will develop at all. The difficulty in long-range forecasting around spring is called the spring predictability barrier. Acting on a wrong estimate can produce unwanted results.
The results were not the same in the two historical events. The initial state of the clouds and the type of El Nino can change the effect. In some model conditions the next La Nina started earlier or became stronger. Unwanted temperature-related changes also appeared in other regions. This makes it clear that improvement in one index is not proof of equal benefit for the whole world. The response after the intervention is removed and the changes in the following years must also be examined.
Scientific limits of the findings
The study used one Earth-system model. It has its own limits in representing processes related to clouds and the ocean-atmosphere link. The researchers themselves stated the need for testing in different models and examination across more types of El Nino events. Finding a process possible in a model is not confirmation of engineering readiness, practical cost or environmental safety. While reading such findings, the study's scope and uncertainty are as important as its potential benefit.
Detaching any figure about the number of ships or the change in temperature from its context can also mislead. They will depend on particular assumptions and the chosen model experiment. A result obtained for one historical event is not proof that it will be repeated in every future event. The value of the research lies in examining a new question; presenting it as a technology ready for use or an immediate solution to an existing weather crisis would be inappropriate.
Caution for India and the monsoon
El Nino has an important relationship with the Indian monsoon, but not every El Nino brings drought to India. NOAA's explanation states that the location of warmth in the Pacific and other climate processes also exert influence. This is a general scientific relationship, not a forecast of any particular year's monsoon. So the model possibility of a weaker El Nino should not lead to claims of definitely higher rainfall, better crops or benefit to all states in India.
Useful priorities for India are: better forecasts of the monsoon, understanding of regional risk, water management and timely information to farmers. The new research can be studied alongside these efforts. But postponing today's adaptation needs in the hope of an uncertain technology can be harmful. The participation of India and other affected countries in international research is also necessary because an experiment conducted in one part of the ocean can affect people far away.
Questions of governance and justice
If such an intervention were ever under consideration in the future, who would decide? Who would assess the potential benefit and harm? How would the views of the people who could be affected be heard? These are not merely laboratory questions. The 2023 expert review of the United Nations Environment Programme emphasised the scientific uncertainties associated with solar radiation modification and the need for equity, consent and governance. That expert review of that time cannot be treated as a substitute for any universal legal permission or prohibition today.
Computer modelling, small outdoor experiments and large operational intervention are different levels. They will need review and monitoring appropriate to their risk. Discussion of open data, independent scrutiny, participation of affected regions and accountability in case of harm is important. Permission to conduct research should not be understood as permission for large-scale use. It would also be an oversimplification to say that no rule or relevant principle of any kind exists at the international level.
Not a substitute for cutting emissions
Sending some sunlight back is not the same as removing carbon dioxide from the atmosphere. The United Nations Environment Programme's review makes clear that solar radiation modification is not a substitute for reducing emissions. Problems linked to extra carbon dioxide, such as ocean acidification, can persist separately. So making potential temporary cooling the basis for continuing dependence on fossil fuels would be wrong. Both emission cuts and preparation for climate impacts remain necessary.
Practice for the Exam
Mains: "Model-based benefits of a climate intervention are not a sufficient basis for permitting its large-scale use." Discuss the questions of scientific uncertainty and international justice with reference to marine cloud brightening. (250 words, 15 marks)
Conclusion
This study of marine clouds offers an opportunity to understand the interconnected processes of the climate. Its usefulness lies in keeping both the possibility and the limit clear. Research can continue, but a claim of safe use demands more evidence, public deliberation and accountability. Current climate action cannot be postponed on the promise of an uncertain future technology.
Sources
- Science Advances: the original model study, 8 July 2026
- University of California San Diego: introduction to the study
- Independent news report of 28 July
- United Nations Environment Programme: introduction to the One Atmosphere review
- One Atmosphere, 2023: preface and key findings
- NOAA: explanation of the El Nino-Indian monsoon relationship