{"id":40507,"date":"2026-01-06T13:28:34","date_gmt":"2026-01-06T13:28:34","guid":{"rendered":"https:\/\/naijaglobalnews.org\/?p=40507"},"modified":"2026-01-06T13:28:34","modified_gmt":"2026-01-06T13:28:34","slug":"we-can-safely-experiment-with-reflecting-sunlight-away-from-earth-heres-how-dakota-gruener-and-daniele-visioni","status":"publish","type":"post","link":"https:\/\/naijaglobalnews.org\/?p=40507","title":{"rendered":"We can safely experiment with reflecting sunlight away from Earth. Here\u2019s how | Dakota Gruener and Daniele Visioni"},"content":{"rendered":"

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T<\/span>he world is warming fast \u2013 and our options to avoid catastrophic harm are narrowing. 2024 was the first full year more than 1.5C hotter than the 19th-century average. Emissions are still rising, with fossil fuel use expected to hit a new high in 2025. Permanent carbon removal technologies \u2013 often cited as a fix \u2013 are removing just tens of thousands of tonnes annually, almost nothing relative to the 5-10bn tonnes needed. Cutting emissions and scaling carbon removal remain essential. But they may not be enough.<\/p>\n

As suffering grows and ecosystems unravel, more people will ask: is there anything we can do to prevent these harms? The idea of reflecting a small fraction of incoming sunlight to reduce warming is not a new idea. In 1965, Lyndon B Johnson\u2019s science advisers proposed it as the only<\/em> way to cool the planet. Earth already reflects about 30% of incoming sunlight; raising that fraction slightly \u2013 say, to 31% \u2013 could strengthen the planet\u2019s natural heat shield. But how?<\/p>\n

In 1991, Mount Pinatubo erupted and sent about 15m tonnes of sulfur dioxide into the stratosphere, cooling the planet by about 0.5C. That eruption became a natural experiment, and inspired the idea of stratospheric aerosol injection (SAI). Models suggest SAI could offset 1C of warming with about 12m tonnes of SO\u2082 per year \u2013 far less than we emit now unintentionally from industrial processes, but with far greater cooling effect.<\/p>\n

Let\u2019s be clear: SAI is no substitute for cutting emissions. If deployed and then suddenly halted, the planet will experience rapid rebound warming. Poorly designed or uncoordinated interventions could shift precipitation patterns in catastrophic ways. But that\u2019s exactly why research is needed \u2013 not to green-light deployment, but to understand whether SAI could ever be used safely, effectively and in the public interest.<\/p>\n

Some argue that the risks of misuse mean it shouldn\u2019t even be studied. We disagree. Careful, open research can clarify whether a well-governed approach could reduce harm, particularly for the most vulnerable. It can also surface risks and failure modes early, making reckless proposals less likely to gain traction. In this sense, research acts as a guardrail \u2013 not a slippery slope.<\/p>\n

But how can we know if something is safe or too risky? We don\u2019t need to reinvent the wheel. Medicine solved the \u201ctoo risky to test\u201d dilemma 60 years ago by codifying phased clinical trials. A similarly structured, stage-gated programme for SAI can safely provide the evidence policymakers will eventually require.<\/p>\n

Right now we\u2019re stuck in \u201cpre-clinical\u201d, or phase zero: lab work and computer models. These are great tools \u2013 they have helped correctly predict the risks of rising emissions \u2013 but we can\u2019t build confidence in their predictions without verifying that they correctly capture key processes for SAI. How do aerosols form, evolve and disperse in the stratosphere? How do they interact with the environment? These are key factors to any robust assessment. What would similar phases as a clinical trial look like for SAI?<\/p>\n

Phase one would involve releasing a tiny amount of SO\u2082 \u2013 approximately 10 tonnes of SO\u2082 (a fraction of what many coal power plants emit in a day) \u2013 at the proper altitudes and carefully measuring its evolution using a suite of instruments: aircraft, ground-based and satellite. This amount would be far too small to affect the climate but would allow researchers to study how aerosols form and behave \u2013 still among the largest scientific uncertainties in the field. Comparing those observations to model predictions would offer an early test of key assumptions and help identify where current projections are robust \u2013 and where they need refinement.<\/p>\n

A potential phase two experiment could be 10 or 100 times larger \u2013 still orders of magnitude smaller than a \u201csmall\u201d volcanic eruption like Mount Ruang, which injected about 300,000 tonnes all at once in 2024 and still had no measurable impact on global climate. <\/em>This would allow researchers to study how aerosols mix and distribute. How quickly do particles spread? How do they interact with stratospheric circulation? Are our models capturing that correctly? If not, what are we missing? Are we observing something totally unexpected? The observational capabilities required for these tests would also be critical to detect an unauthorized deployment.<\/p>\n

After researchers worldwide had the opportunity to peruse the data and draw their own conclusions, the evidence could be put to a decision: are governments interested to move forward with something that starts looking like a deployment? If yes, research would move into a phase three \u2013 akin to a post-licensure, phase four trial in medicine \u2013 involving small, deliberate cooling, perhaps about 0.1C over five years under constant observation and strict oversight. Such slow (and reversible) deployment, if coupled to a strong governance framework, would be the opposite of a rogue or reckless deployment.<\/p>\n

The world may never need to reflect sunlight. But if it does, the only way to make a future responsible decision about its use will be to generate real-world evidence, transparently, before<\/em> a crisis forces our hand. That means building the tools, rules and oversight mechanisms now, not later.<\/p>\n

We see the UK\u2019s Advanced Research and Invention Agency (Aria) program as a strong first step in that direction. At the lab that one of us runs, a new Aria-funded project is developing the theoretical foundations to determine the minimum<\/em> scale at which an outdoor experiment could meaningfully reduce key uncertainties \u2013 essential groundwork for any future research to be done safely and transparently. And at Reflective, the organization that one of us leads, we\u2019re working to support open science, careful coordination and strong public accountability across the field.<\/p>\n

Outdoor research is not a slippery slope to deployment. It\u2019s how we make sure that any future decision \u2013 whether to move forward, reject the idea entirely or refine it \u2013 is based on facts, not fear or wishful thinking. Done right, small-scale experiments can reduce both scientific uncertainties and political risks. The real danger isn\u2019t asking the question. It\u2019s waiting too long to learn the answer.<\/p>\n