This week the UN Environment Assembly considered a resolution on solar radiation modification that deals with controversial technologies designed to mask the warming effect of greenhouse gases by reflecting sunlight back into space.

Proponents argue the technology will limit the effects of climate change. In fact, such “geoengineering” risks further destabilizing an already deeply disturbed climate system. At best, its full impact will not be known until distribution. The draft decision initially called for the convening of an expert panel to study the benefits and risks of varying solar radiation. The proposal was withdrawn on Thursday after failure to reach consensus on the controversial issue.

A notable event was the call by some countries in the South to “not use” modification of solar radiation. We strongly support this position. Human-caused climate change is already too much experimentation across the planet; We don’t need another experiment.

risky business

Solar geoengineering is gaining traction in some circles as a solution to the climate crisis. However, studies have consistently identified potential risks associated with technologies such as:

• Unforeseen impacts on climate and weather conditions
• loss of biodiversity, especially if the use of technology is suddenly stopped
• weakening food security, for example through reduced light and increased salinity on land
• human rights violations across generations – including but not limited to the transfer of enormous risks to the generations that follow us.

Here we discuss several examples of solar radiation modification that illustrate the threats posed by these technologies. They are also shown in the picture below.

hot air load

In April 2022, an American startup company launched two weather balloons from Mexico. The experiment was carried out without permission from Mexican authorities. The aim was to cool the atmosphere by deflecting sunlight. The resulting reduction in heating will be sold for profit as “cooling credits” to those who want to offset greenhouse gas pollution.

Significant climate cooling would essentially require millions of metric tons of aerosol to be injected into the stratosphere by a fleet of purpose-built high-altitude aircraft. Such an initiative would alter global wind and precipitation patterns, leading to more droughts and hurricanes, more acid rain, and slower ozone recovery.

Once initiated, stratospheric aerosol injection will need to be performed continuously for at least a century to achieve the desired cooling effect. An early lockdown would lead to an unprecedented rise in global temperatures that would far outpace extreme climate change scenarios.

heads in the clouds

Another solar geoengineering technology, known as marine cloud illumination, aims to make low-lying clouds more reflective by spraying microscopic seawater droplets into the air. Tests have been continuing in the Great Barrier Reef since 2017. The project is small-scale and involves pumping seawater into the boat and spraying it into the sky through nozzles. The project manager said the fog machine would have to be enlarged tenfold to about 3,000 nozzles to lighten nearby clouds by 30%.

After years of testing, the project has yet to produce peer-reviewed empirical evidence that cloud brightening can lower sea surface temperatures or protect corals from bleaching. The Great Barrier Reef is the size of Italy. Scaling up cloud lighting efforts requires up to 1,000 machines on boats that pump and spray large amounts of seawater for months during the summer months. Even if it works, the operation is not as “environmentally sound” as its advocates claim.

The effects of the technology remain unclear. For the Great Barrier Reef, less sunlight and cooler temperatures can alter water movement and mixing, harming marine life. Marine life may also be destroyed by the pumps or negatively affected by additional noise pollution. On land, the weakening of sea clouds may cause a change in the precipitation regime and an increase in salinity, which may harm agriculture.

More broadly, 101 governments last year adopted a declaration describing marine geoengineering, including cloud lighting, as having “the potential for widespread, long-lasting or severe adverse effects.”

Balls, bubbles and foam

The Arctic Ice Project involves spreading a layer of tiny glass spheres over large areas of sea ice to illuminate its surface and stop ice loss. Tests were conducted on frozen lakes in North America. Scientists recently showed that the spheres actually absorb some sunlight, accelerating the loss of sea ice under some conditions.

Another suggested intervention is to spray microbubbles or sea foam into the ocean to make the surface more reflective. This will lead to the use of large concentrations of chemicals to stabilize bubbles or foam on the sea surface, posing a significant risk to marine life, ecosystem functioning and fisheries.

No more distractions

Some scientists researching solar geoengineering discuss the need for “exit ramps”; stopping research when a proposed intervention is deemed technically impossible, too risky, or socially unacceptable. We think we have already reached this point.

More than 500 scientists from 61 countries have signed an open letter calling for an international agreement not to use solar geoengineering starting in 2022. In addition to the types of risks discussed above, the letter notes that speculative technologies are a distraction from the urgent need to reduce global emissions and that there is no global governance framework to fairly and effectively regulate their implementation.

Calls for outdoor technology trials are misguided and divert energy and resources away from what we need to do today: phase out fossil fuels and accelerate a globally just transition.

Climate change is the greatest challenge facing humanity, and global responses are woefully inadequate. Humanity should not pursue dangerous distractions that do not address the root causes of climate change, carry great risk, and are likely to further delay climate action.