Harvard scientists identify aerosol that can cool the planet and repair the ozone layer at the same time

The Paris Agreement is a historic global effort to combat global warming by taking steps to reduce carbon based emissions. However, just reducing emissions may not be enough to tackle the problem. A drastic measure for geoengineering the atmosphere is to release large amounts of sulfate aerosols in the atmosphere, which happen naturally after major volcanic eruptions. These aerosols cool down the atmosphere by reflecting sunlight back into space. However, the problem is that the same aerosols also damage the ozone layer, leading to increased risk of UV light exposure.

The UV light exposure can adversely affect human beings, by causing eye damage and increasing the chances of skin cancer. Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have found an aerosol that not only cools the atmosphere, but repairs the ozone layer at the same time. The research is published in the Proceedings of the National Academy of Sciences.

"This research is a turning point and an important step in analyzing and reducing certain risks of solar geoengineering,” said David Keith, the Gordon McKay Professor of Applied Physics at SEAS.  Frank Keutsch, the Stonington Professor of Engineering and Atmospheric Science at SEAS said "Essentially, we ended up with an antacid for the stratosphere."

Previous research in the area was focused on nonreactive aerosols to reduce the damage done to the ozone layer. The Harvard researchers focused on highly reactive aerosols, that can have potentially beneficial effects. The researchers scanned the periodic table to identify potential candidates for geoengineering. After a process of eliminating unpredictable elements, rare earth metals and toxic substances, Alkali and Alkaline Earth metals emerged as potential candidates.

The researchers are testing the use of calcite in lab environments that simulate the atmosphere. The research teams will be a part of the Harvard Solar Geoengineering Research Program, to be launched next year. The interdisciplinary program is expected to be one of the most extensive and far reaching solar geoengineering research effort ever undertaken.