If they get approval, Harvard scientists are planning to send an aerosol-injecting balloon into the stratosphere this June
23 March, 2021
Harvard University scientists are proposing a June 2021 test flight of a balloon aircraft designed to inject the stratosphere with chalky dust in hopes of partially blocking out the sun to combat global warming.
“It’s a small scale experiment that will inject about a kilogram of particles into the stratosphere to generate a plume a few kilometers in length that will have absolutely no physical impact on the ground,” says Harvard Engineering and Atmospheric Science Professor Frank Keutsch in a video.
The several-million dollar experiment – which is set to take place in Sweden – has been funded by private donors, including Microsoft co-founder Bill Gates.
It’s designed to mimic the effects of a volcano, which has the temporary effect of blocking out some of the sun’s light and heat with its plumes of volcanic sulfuric ash, but critics warn trying to outsmart nature is rife with risks.
In their first test, the Harvard scientists want to use calcium carbonate, instead of sulfates, which can lead to ozone loss. “But because calcium carbonate does not exist naturally in the stratosphere, models for its behavior are uncertain,” admits David Keith, a Harvard energy and climate scientist.
“Even if it doesn’t deplete ozone, calcium carbonate will react with other gases and particles in the stratosphere, changing its composition— and potentially seed clouds in the lower atmosphere that might cool or warm the planet,” Perdue University atmospheric chemist Daniel Cziczo, who is skeptical of the experiment tells Science Magazine.
Even with all the risks, proponents claim we can’t cut greenhouse gas emissions fast enough to avoid climate disaster, and that “dimming the sun may be our only choice.”
The first flight in June would not inject any particles. It would only be a dry run of the steerable balloon and instruments. If all goes well, the experiment would inject up to 2 kilograms of calcium carbonate into the stratosphere, which, Harvard points out, is about how many aerosols commercial airplanes emit every minute.