Scientists at Harvard University are planning to release calcium carbonate particles into the stratosphere in an attempt to artificially cool the Earth. The idea is based on the observation that the Earth cooled by 0.4 degrees Celsius after the 1991 eruption of the Pinatubo volcano in the Philippines, which released large amounts of dust and aerosols into the atmosphere. The scientists hope that the particles will reflect sunlight and direct it back into space, thereby reducing the amount of heat absorbed by the Earth. The experiment, known as the Stratospheric Controlled Perturbation Experiment (Scopex), will involve releasing the particles from a balloon at an altitude of 20 kilometers. The balloon will also carry instruments to analyze the chemical and physical processes within the artificial cloud.
The first test flight of the balloon is scheduled for June 2021 over Sweden, but it will not release any calcium carbonate particles. Instead, it will be a “dry run” to test the functions of the balloon under real conditions. The experiment has been met with controversy, as the release of sulfur aerosols from the Pinatubo volcano caused cooling but also damaged the ozone layer. While calcium carbonate is less reactive than sulfur aerosols, the effects of its release on the atmosphere are not yet fully understood. The scientists plan to start with a small-scale experiment using 100 to 2,000 grams of calcium carbonate to minimize the risk. However, even the scientists involved in the project have expressed reservations about the method, citing the unknown side effects and the risk of dependence on the technology.
Despite the risks, the Scopex team believes that it is important to explore all options for climate control, as it may be one of the last options available to humanity in the face of rapid global warming. However, they acknowledge that the technology only addresses the symptoms of climate change and not the root causes, and that constant releases of particles into the atmosphere may be necessary to prevent a rapid temperature increase. The experiment has yet to receive approval from an independent expert panel appointed by Harvard University.
