Questions about Solar radiation modification
Short answers, pulled from the story.
What is solar radiation modification and how does it work?
Solar radiation modification (SRM), also called solar geoengineering, is a group of large-scale approaches to reduce global warming by increasing the amount of sunlight reflected away from Earth and back into space. Methods include stratospheric aerosol injection, which introduces small reflective particles into the upper atmosphere, and marine cloud brightening, which increases the reflectivity of ocean clouds. A 1% increase in Earth's planetary albedo could reduce radiative forcing by 2.35 W/m2.
Who first proposed solar radiation modification as a climate response?
The concept traces to 1965, when the President's Science Advisory Committee delivered a report to US President Lyndon B. Johnson warning of harmful carbon dioxide emissions and mentioning the possibility of raising Earth's reflectivity. In 1974, Russian climatologist Mikhail Budyko proposed that aircraft burning sulfur could generate reflective stratospheric aerosols to cool the planet. Nobel Laureate Paul Crutzen published an influential paper in 2006 calling for serious research into SRM's feasibility and environmental consequences.
What are the main risks of stratospheric aerosol injection?
Stratospheric aerosol injection risks include delaying the recovery of stratospheric ozone, particularly if sulfates are used. Regional precipitation patterns, especially tropical monsoon intensity, could be disrupted. SRM does not reduce atmospheric carbon dioxide, so ocean acidification would continue. If deployment were abruptly terminated, the climate would rapidly warm toward previously suppressed levels, a phenomenon called termination shock.
How much has been spent on solar radiation modification research?
Through 2024, roughly 200 million US dollars had been spent on SRM research globally, with the annual rate rising to more than 30 million dollars in recent years. As of May 2025, an additional 164 million dollars had been committed for 2025-2029. Governments account for 42% of funding and philanthropies for 48%, with the UK, the United States, and foundations linked to donors including Bill Gates and Sam Altman among the largest contributors.
Is there an international law governing solar geoengineering?
No comprehensive global framework exists to regulate SRM research or deployment. The Environmental Modification Convention prohibits hostile environmental modification with severe transboundary effects but permits peaceful uses. The Convention on Biological Diversity established a non-binding normative framework in 2010 requiring environmental assessment and regulatory oversight for climate-related geoengineering activities. The Oxford Principles, developed by academics, remain the most prominent voluntary framework.
Why do some US states want to ban solar geoengineering?
Since 2024, lawmakers in at least 28 US states have introduced or supported bills to prohibit SRM or related practices, largely influenced by the chemtrails conspiracy theory. Tennessee enacted such a law in 2024, signed by Governor Bill Lee, and Florida followed with a similar law signed by Governor Ron DeSantis. These bills target weather modification and SRM broadly, though they are not aimed at specific scientific research programs.