"The Controversial Harvard Study on Sun-Dimming: What Comes Next?"

The sun-dimming experiment, known as the Stratospheric Controlled Perturbation Experiment (SCoPEx), was set to be the first to test the injection of particles into the Earth's upper atmosphere to measure their ability to reflect sunlight back into space. The experiment aimed to determine if such a technique could provide emergency relief from the worst impacts of climate change, as governments struggle to limit greenhouse-gas emissions.

However, the study faced opposition from those concerned about potential unintended consequences and the lack of international consensus on solar geoengineering. Opponents also worry that it could reduce pressure on world leaders to eliminate greenhouse-gas emissions by offering a 'plan B'.

The Harvard team had planned to launch a high-altitude balloon into the stratosphere, releasing up to 2 kilograms of calcium carbonate particles, and then measure their dispersal, interaction with other chemicals, and ability to reflect sunlight. However, the first launch, intended as an equipment test and set to take place at the Esrange Space Centre in northern Sweden, was called off in 2021 after environmentalists and local Indigenous groups announced their opposition.

The cancellation of the Harvard study, however, has not halted all research in this field. Independent researcher Andrew Lockley launched a low-cost balloon that released 400 grams of sulfur dioxide into the stratosphere in 2022, and a for-profit company called Make Sunsets has begun dispersing sulfur dioxide into the stratosphere by balloon. Meanwhile, the US National Oceanic and Atmospheric Administration (NOAA) has begun gathering background data from the stratosphere to better understand potential solar geoengineering efforts.

Despite the controversy, scientists say that discussions about solar geoengineering aren't going away. The World Climate Research Programme has launched an initiative to promote research into climate interventions such as solar geoengineering, and scientists are working to build the world's largest academic initiative focused on climate engineering at the University of Chicago.

While some argue that such experiments should not proceed without broad public input, others argue that small experiments that are not expected to impact the environment should not require a global process.

As climate change continues to pose significant threats to the planet, the debate over sun-dimming experiments and solar geoengineering is likely to continue.

Source: <https://www.nature.com/articles/d41586-024-00876-1>