High-Profile Geoengineering Experiment Shuts Down

A beleaguered solar geoengineering project failed to conduct field tests because of opposition from environmentalists and Indigenous residents

By Chelsea Harvey & E&E News

The idea of spraying substances into the atmosphere to reflect sunlight has raised concerns among some scientists.

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chuchart duangdaw/Getty Images

CLIMATEWIRE | Harvard University ended a solar geoengineering research project after years of setbacks derailed efforts to infuse small parts of the sky with sunlight-blocking aerosols.

The principal investigator, Harvard researcher Frank Keutsch, is “no longer pursuing the experiment,” the university announced Monday.

Known as SCoPEx, short for “stratospheric controlled perturbation experiment,” the project focused on a form of geoengineering often referred to by scientists as solar radiation modification. The idea — largely hypothetical for now — is that humans can artificially lower the Earth’s temperatures by spraying reflective materials, such as sulfates, into the atmosphere. These reflective aerosols could then beam sunlight back out to space, cooling the planet and combating the effects of climate change.

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It’s a contentious idea. Proponents of solar geoengineering research argue that scientists should explore all possible avenues to address the planet’s rapidly rising temperatures. But scientists caution that solar geoengineering could carry a wide array of unintended side effects, including negative impacts on the Earth’s ozone layer or weather patterns.

Experts have also warned that solar geoengineering, if begun on a large scale, would be difficult to safely stop. Most reflective aerosols don’t last very long in the atmosphere, meaning they’d need to be sprayed constantly in order to maintain a cooler planet. If the spraying suddenly stopped, global temperatures could skyrocket so rapidly that they could threaten life on Earth — a phenomenon known among geoengineering experts as “termination shock.”

The Harvard project has been winding down for months. Researchers announced their intention to suspend the experiment last August, according to Monday’s statement.

Keutsch said he felt it was “time to focus on other innovative research avenues” in the solar geoengineering field.

“I have learned important lessons about governance and engagement throughout the course of this project – and created an instrument that can be used for vital stratospheric research unrelated to solar radiation management (SRM),” he said in an email to E&E. “At the same time, the field of SRM has undergone a signification transformation in the last few years, expanding the community and opening new doors for research and collaboration.”

A SCoPEx advisory committee also released its final report Monday, summarizing its efforts to develop a comprehensive governance and oversight framework for the project over the last few years and outlining recommendations for future research initiatives. The report emphasized the need for scientists to engage meaningfully with local communities that could be affected by geoengineering projects.

It’s a lesson the SCoPEx team learned the hard way. In 2021, the researchers planned to carry out one of its first tests in the Arctic city of Kiruna, Sweden. But the team suspended its plans after opposition from environmental groups and Indigenous communities in the region.

The potential side effects of geoengineering remain poorly understood, and most scientific research on its outcomes has been theoretical and often conducted with the help of computer models.

SCoPEx, which officially launched in 2019, was among the first to propose real-world field experiments on geoengineering. The researchers planned to start with small, highly controlled trials, releasing small amounts of calcium carbonate, sulfates or other materials from a high-altitude balloon. They would then collect measurements on how the aerosols behaved in the atmosphere.

The researchers settled on Sweden for their first trials in 2021. Yet the project quickly erupted in controversy after environmental and Indigenous groups expressed their concern about the potential risks associated with solar geoengineering and the project’s lack of engagement with local communities.

Critics have increasingly raised concerns about the need for governance and oversight for geoengineering field trials. In 2022, climate tech company Make Sunsets began releasing weather balloons filled with sulfur dioxide in the Mexican state of Baja California, the world’s first documented solar geoengineering effort. The act was met with widespread concern and outrage, and the startup announced last year that it would halt its operations in Mexico after the Mexican government declared it would prohibit geoengineering in the country.

Despite the controversies, some top scientists have continued to cautiously advocate for more research — as long as it’s closely governed and heavily regulated.

In 2021, the National Academies of Sciences, Engineering and Medicine released a report recommending that the federal government develop a national research program focused on solar geoengineering. But the report also recommended clear governance frameworks and a heavy emphasis on local engagement and social concerns about potential risks.

The SCoPEx advisory committee’s final report echoed those recommendations. Over the last few years, the committee developed a five-step framework for the SCoPEx experiment that could be applied to future projects. The steps include conducting comprehensive reviews on engineering safety, finances, legal issues, the project’s scientific merit and societal engagement with the research.

Contemplating societal engagement occupied much of the advisory committee’s time and effort, the report noted. The committee further outlined four core principles for social engagement in future projects. Engagement efforts should: begin as early as possible, include social scientists, avoid making advance assumptions about local communities’ concerns and develop a plan to respond.

While SCoPEx has come to an end, Harvard will maintain its Solar Geoengineering Research Program. The university noted that the program will continue to “explore the many dimensions of this issue, including the science and engineering, governance, and political and social implications.”

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