If the climate is more sensitive to GHG emissions than consensus estimates suggest, carbon pricing and other measures designed to nudge consumers and firms into reducing emissions aren’t likely to make much of a difference. That is why David G. Victor, M. Granger Morgan, Jay Apt, John Steinbruner, Katharine Ricke call for small-scale field tests of solar radiation management (SRM) technologies that could change the planet’s energy balance quite quickly:
The usual proposals involve spraying material into the stratosphere, where it would turn into reflective clouds, or blowing seawater into the air, with a similar effect. The clouds could deflect just enough incoming sunlight to offset, crudely, the number of degrees human emissions have warmed the planet. Flying a fleet of high-altitude aircraft that spray particles into the upper atmosphere would cost perhaps ten billion dollars per year — a pittance for a country that is suffering from severe climate change and seeks a quick solution.
Most carbon dioxide removal schemes appear relatively safe, although tinkering with a fragile ecosystem by fertilizing the ocean does involve risks. In contrast, SRM raises serious political and policy questions. Although quick and cheap, messing with the complex and imperfectly understood climate system, which is already stressed by warming gases, could end badly. Severe side effects might, for example, include a shift in the seasonal monsoons that many countries rely on for rainfall and agriculture, or accelerate the destruction of the ozone layer. No one knows whether it would be possible to predict and offset all such harmful side effects or how much it might cost.
Because our understanding of how SRM technologies would work in practice is very limited, there is a great deal of reluctance to make substantial investments in such Plan B measures. And so it’s time to start with tests that are small enough not to have durable impacts on the climate system. With any luck we’ll hit upon an affordable “insurance policy” to guard against sudden, catastrophic climate change.