“The technical modification of solar radiation is not a solution in the fight against human-induced climate change . Trying to ‘repair’ the climate with large-scale technical projects is associated with incalculable risks and would jeopardise our peace, our security and the stability of societies,” says UBA President Dirk Messner. “Solar Radiation Modification is also not an emergency option, not a transitional technology and certainly not a licence to ease up on avoiding greenhouse gas emissions.”
Various SRM approaches
SRM encompasses several large-scale technological approaches to mitigate human-induced global warming. SRM is based on the idea of reducing the amount of solar radiation reaching the earth or increasing the reflection of solar radiation (albedo). The five most discussed SRM approaches are:
- Aerosols in the stratosphere: Deployment of tiny particles at an altitude of around 20 kilometres so that they reflect some of the sun's rays before they reach the earth.
- Lightening of clouds over the sea: “Bleaching” of clouds over the oceans, for example by salt particles from seawater, so that they reflect more sunlight.
- Installations in space: Creating a partial shade in space using a giant solar sail so that less sunlight hits the earth.
- Thinning of cirrus clouds: Thinning cirrus clouds (at an altitude of five to 13 kilometres) using chemicals to allow more infrared radiation to escape into space.
- Brightening the Earth's surface: Increasing the reflectivity of the Earth's surface (also known as surface albedo) by using reflective materials and white paint, for example on farmland, icy surfaces, deserts or in cities.
Unpredictable risks from SRM
SRM would mean an extensive and difficult-to-calculate intervention in the Earth's climate system. It could change global precipitation patterns (e.g. in monsoon regions), which would threaten water and food security. It would not achieve a uniform global cooling effect, but would result in continued warming in some regions and excessive cooling elsewhere. SRM would threaten ecosystems on land and in the oceans, would jeopardise efforts to increase climate action and reduce CO2 emissions and could lead to far-reaching geopolitical tensions.
The UBA warns of the unforeseeable consequences of this type of technical influence on the climate. UBA President Dirk Messner comments: “Effective climate action that focuses on reducing climate-damaging greenhouse gas emissions is already technically and socially feasible today, and is what society is looking for. SRM is not climate action!”
Further information:
The 64-page UBA technical brochure “Solar Radiation Modification (SRM): Effects, risks and governance of intervention in the global climate system through solar geoengineering” summarises the scientific findings on the individual processes, the risks and the approaches for international regulation of SRM. It explains the theoretical basis behind the idea of SRM, presents the research activities and the associated difficulties and also addresses narratives and justifications for SRM.
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