- The “speculative group of technologies” that involve reflecting sunlight away from the Earth and back toward space, often called solar radiation modification, or more broadly solar geoengineering, should not be used now, the United Nations said, but they should be studied more rigorously.
- Reflecting sunlight away from the Earth is dangerous, but it is also doable and quick, which means that if climate change-mitigation strategies continue to be insufficient, it could become a viable option.
- There also needs to be international governance rules established for any possible use of sunlight-reflection technology, especially because the relatively low cost and relatively simple technology make it possible for a “rogue deployment.”
Global efforts to respond to climate change are so far insufficient, making it time to begin studying technologies to reflect sunlight away from the Earth to cool it down temporarily, said a new report from the United Nations published on Monday.
Reducing greenhouse gas emissions is the only way to permanently slow global warming, but worldwide efforts to reduce greenhouse gas emissions are currently “not on track to meet the 1.5° Celsius Paris Agreement goal,” the U.N. Environment Program said in a written statement accompanying the release of the report.
The report on these technologies, written by an expert panel brought together by the U.N. program, advised that it’s currently not a good idea to use them in an effort to respond to climate change.
However, “this view may change if climate action remains insufficient,” the report said, signaling that it’s time for rigorous study of both the technologies and the potential international governance.
A similar message came from a group of more than 60 scientists in an open letter that was also (coincidentally) published on Monday.
Fast and doable, but potentially dangerous
Solar geoengineering “is the only known approach that could be used to cool the Earth within a few years,” the U.N. report said, and would cost tens of billions of dollars per year per degree of cooling.
While the technology to inject large quantities of aerosols into the upper atmosphere does not exist today, it’s not seen as being terribly complicated: “No show-stopping technical hurdles have been identified,” the U.N. report said, and it could be “developed in under ten years.”
Scientists know it works quickly, citing the drop in the global average temperature after large volcanic eruptions have spread large quantities of aerosols into the upper atmosphere. These observations of volcanic activity provides “strong evidence that a deliberate injection of large amounts of reflective particles into the stratosphere would cool the Earth rapidly,” the U.N. study said.
“If global warming at some point produces outcomes widely seen as intolerable (e.g. widespread famines, mass migration, mass mortality and destruction of infrastructure) an operational SRM deployment as part of a ‘planned’ emergency response might be able to alleviate some of this suffering within a few years,” according to the report.
But the techniques can also be dangerous.