The United Nations Environment Assembly this week considered a resolution on solar radiation modification, which refers to controversial technologies intended to mask the heating effect of greenhouse gases by reflecting some sunlight back to space.
Proponents argue the technologies will limit the effects of climate change. In reality, this type of “geoengineering” risks further destabilizing an already deeply disturbed climate system. What’s more, its full impacts cannot be known until after deployment.
The draft resolution initially called for the convening of an expert group to examine the benefits and risks of solar radiation modification. The motion was withdrawn on Thursday after no consensus could be reached on the controversial topic.
A notable development was a call from some Global South countries for “non-use” of solar radiation modification. We strongly support this position. Human-caused climate change is already one planetary-scale experiment too many – we don’t need another.
Here, we discuss several examples of solar radiation modification which exemplify the threats posed by these technologies. These are also depicted in the graphic below.
A load of hot air
In April 2022, an American startup company released two weather balloons into the air from Mexico. The experiment was conducted without approval from Mexican authorities.
The intent was to cool the atmosphere by deflecting sunlight. The resulting reduction in warming would be sold for profit as “cooling credits” to those wanting to offset greenhouse gas pollution.
Appreciably cooling the climate would, in reality, require injecting millions of metric tons of aerosols into the stratosphere, using a purpose-built fleet of high-altitude aircraft. Such an undertaking would alter global wind and rainfall patterns, leading to more drought and cyclones, exacerbating acid rainfall and slowing ozone recovery.
Once started, this stratospheric aerosol injection would need to be carried out continually for at least a century to achieve the desired cooling effect. Stopping prematurely would lead to an unprecedented rise in global temperatures far outpacing extreme climate change scenarios.
Heads in the clouds
Another solar geoengineering technology, known as marine cloud brightening, seeks to make low-lying clouds more reflective by spraying microscopic seawater droplets into the air. Since 2017, trials have been underway on the Great Barrier Reef.
The project is tiny in scale, and involves pumping seawater onto a boat and spraying it from nozzles towards the sky. The project leader says the mist-generating machine would need to be scaled up by a factor of ten, to about 3,000 nozzles, to brighten nearby clouds by 30%.
After years of trials, the project has not yet produced peer-reviewed empirical evidence that cloud brightening could reduce sea surface temperatures or protect corals from bleaching.
The Great Barrier Reef is the size of Italy. Scaling up attempts at cloud brightening would require up to 1,000 machines on boats, all pumping and spraying vast amounts of seawater for months during summer. Even if it worked, the operation is hardly, as its proponents claim, “environmentally benign”.
The technology’s effects remain unclear. For the Great Barrier Reef, less sunlight and lower temperatures could alter water movement and mixing, harming marine life. Marine life may also be killed by pumps or negatively affected by the additional noise pollution. And on land, marine cloud brightening may lead to altered rainfall patterns and increased salinity, damaging agriculture.
Source: https://studyfinds.org/cooling-earth-blocking-sunlight/
