Modern efforts to clean up air pollution started in the 1950s following the London Smog event, which killed nearly 12,000 people. Much of that pollution was caused by sulphate aerosols. The health and environmental impacts of sulphate pollution were well understood by the 2000s, but another impact was becoming increasingly clear: sulphate aerosols reflected incoming solar radiation, preventing some global warming. The realization that clean air legislation was contributing, in part, to global warming, led Paul Crutzen, a Nobel Prize-winning atmospheric chemist, to make an unorthodox suggestion in 2006: what if we added sulfate particles into the upper atmosphere, purposefully, to reflect sunlight while avoiding negative health impacts? Would it avoid the health impacts?

This episode explores the history and risks of the sunlight reflection method known as stratospheric aerosol injection (SAI), and its relationship to air pollution. We’re joined by Oliver Morton, Senior and Briefings Editor at The Economist, and Daniele Visioni, Assistant Professor of Earth and Atmospheric Science at Cornell University.

Climate Reflections is a production of SRM360, a non-profit knowledge hub supporting an informed, evidence-based discussion of sunlight reflection methods. For more information and the latest research on SRM, visit SRM360.org.

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