New research study: “The sky is not the limit” for

There are practical limits to how high aerosols can be deployed in the atmosphere to deflect incoming sunlight and counteract global warming. According to a new study published today in Communication of environmental research.

Next to a landmark study in 2018 which clarified the lofting technologies by which it would be possible to undertake solar geoengineering, the new report is the first to assess the safety and cost-effectiveness of deployment at an altitude of 25 km. The report responds directly to a question posed by the US National Academy of Sciences, Engineering, and Medicine in a historical study in March 2021 which recognized the need for further research into the viability of aerosol deposition well above 20 km.

Wake Smith, the study’s lead author, says: “This finding is expected to change the way climate intervention models are run globally and shows that practical limits must be weighed against effectiveness. radiation in the design of solar geo-engineering programs.

Several major studies over the past decade have noted that deployment of stratospheric aerosols at an altitude of 25 km would be more efficient than at 20 km, leading climate modelers to routinely incorporate such high deployments into their studies. . For reference, airliners and military aircraft routinely cruise close to 10km, while 20km is the domain of spy planes and high-flying drones. Planning hundreds of thousands of annual solar geoengineering deployment flights at altitudes inaccessible to even elite spy planes would not only dramatically increase costs, but pose unacceptable security risks to flight crews, aircraft and the public not involved on the ground.

According to Smith, “There is a ceiling in the sky above which traditional aircraft cannot operate, and 25 km lies above it.”


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Paul N. Strickland