Can ‘antacids’ tackle climate change?

• Scientists say aerosols could cool planet without ozone damage
As global temperatures rise, scientists are working on ways to slow down climate change.

New research suggests that pumping the equivalent of ‘antacid’ tablets into the air could be the answer.

The research is published in the Proceedings of the National Academy of Sciences.

Unlike previous suggestions, experts believe that releasing an aerosol of calcium carbonate into the atmosphere would cool the air, without damaging the ozone layer.

After examining stratospheric chemistry and ruling out most of the periodic table, the researchers landed on calcite – a constituent of limestone. It is the most stable form of calcium carbonate. They found that this could neutralise emission-based acids in the atmosphere while also reflecting light and cooling the planet.

Calcite is one of the most common compounds in the Earth’s crust, and only a small amount would be needed for the solar geoengineering.

Last year’s Paris climate agreement set the goal of keeping global temperatures no higher than 1.5 degrees Celsius above the ‘pre-industrial levels’.

Emission reductions will be key to achieving these, but the researchers believe that extra efforts can further reduce the risks.

One idea suggested in the past was to ‘geoengineer’ the Earth to mimic the cooling effect seen in the air following a large volcanic eruption, which shoots up large amounts of sulphur dioxide.

This would be achieved by pumping light-reflecting sulphate aerosols into the stratosphere.

However, this is risky, as they would produce sulphuric acid, which damages ozone.

A study from researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) suggests a similar approach, but without the risk associated with sulphur dioxide.

“In solar geoengineering research, introducing sulfuric acid into the atmosphere has been the only idea that had any serious traction until now,” said David Keith, professor of Applied Physics at SEAS and Professor of Public Policy at the Harvard Kennedy School, United States, and first author of the paper.

“This research is a turning point and an important step in analyzing and reducing certain risks of solar geoengineering.”

Previous research had focused on ways of limiting the ozone damage by using non-reactive aerosols.

However, the new research looked at highly reactive aerosols.

“Instead of trying to minimise the reactivity of the aerosol, we wanted a material that is highly reactive but in a way that would avoid ozone destruction,” said co-author Frank Keutsch.

After examining stratospheric chemistry and ruling out most of the periodic table, the researchers landed on calcite – a constituent of limestone.

They found that this could neutralise emission-based acids in the atmosphere while also reflecting light and cooling the planet.