Bill Gates
Source: Getty Images

Bill Gates’ Sun-Dimming Study Could Help Cool the Earth—If It Ever Launches


Apr. 21 2021, Published 3:35 p.m. ET

The idea of using geoengineering to stop global warming sounds like science fiction, as anyone who has seen Snowpiercer can attest. But a sun-dimming study backed by billionaire philanthropist Bill Gates is very real. 

The only problem? The study is literally having trouble getting off the ground. As reported on April 1, scientists called off a test balloon flight that was scheduled to take place in Sweden this June.

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Here's some more information on this very real scientific proposal and some of the controversies surrounding the Bill Gates-backed "sun dimming" study.

The idea isn't truly to dim the sun but to reflect sunlight away from the Earth.

The hypothesis behind the sun dimming proposal involves releasing particles into the atmosphere to reflect some of the Sun’s light back into space, thus cooling the Earth and reducing the effect of the greenhouse effect.

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Source: Getty Images

As Nature reported in 2019, scientists observed that the Earth’s average temperature dropped by half a degree Celsius after the 1991 eruption of Mount Pinatubo erupted in the Philippines sent an estimated 20 million tons of sulfur dioxide into the stratosphere.

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Now researchers want to use calcium carbonate—a compound used in paper, cement, toothpaste, and antacids—to test whether a similar cooling effect can be achieved. One estimate, according to the magazine, claims that sun-reflecting particles could reduce temperatures around the globe by around 1.5 degrees Celsius at a cost of less than $10 billion per year.

The sun-dimming project, called the Stratospheric Controlled Perturbation Experiment (SCoPEx), began as a collaboration between atmospheric chemist James Anderson of Harvard and experimental physicist David Keith, according to Nature. The magazine also reported that Keith used research funding from Gates to start the experiment.

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The test was postponed, likely until 2022, amid divisions in the scientific community.

The plan was to launch a high-altitude test balloon from the Esrange Space Center in Kiruna, a town in the far north of Sweden, to determine whether the balloon could carry equipment to release the particles into the atmosphere.

But the project sparked criticism from people who worried the particles would harm both the ozone layer and ecosystems closer to terra firma. According to, some scientists and environmentalists view the project as dangerous.

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Ultimately, the Swedish Space Corporation (SSC) opted against the test flight after consulting experts and stakeholders. “The scientific community is divided regarding geoengineering,” the state-owned corporation said in a statement, per “SSC decided not to conduct the technical test flight planned for this summer.”

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Additionally, a special committee at Harvard—set up to analyze the project’s societal and ethical implications—also supported postponing the flight to give researchers more time to review the project’s impact on Sweden and the indigenous Sami people in particular. “Societal engagement should occur in Sweden before any SCoPEx research is conducted in the country,” the committee stated, adding that the launch likely won’t happen until 2022.

“SCoPEx is the first out of the gate, and it is triggering an important conversation about what independent guidance, advice, and oversight should look like,” says Peter Frumhoff, chief climate scientist at the Union of Concerned Scientists in Cambridge, Mass., told Nature. “Getting it done right is far more important than getting it done quickly.”


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