Controversial Harvard Geoengineering Project Abandoned After Advisory Committee Report


A controversial environmental geoengineering experiment led by Harvard Chemistry professor Frank N. Keutsch is officially no longer being pursued, according to a Monday statement from the Salata Institute for Climate and Sustainability.

The Stratospheric Controlled Perturbation Experiment, commonly known as SCoPEx, was initiated by Keutsch and Applied Physics professor David W. Keith and had a preliminary goal of gathering data on atmospheric conditions in order to learn more about the impact of aerosols on the stratospheric environment.

The decision to abandon the experiment comes 10 years after the idea was initially conceived. In 2019, Harvard formed an external advisory committee to provide a governance framework for the SCoPEx project.

The committee released its final report about SCoPEx on Monday, which coincided with Keutsch’s announcement that he would no longer move forward with the project. While the advisory committee’s final report recognized the decision to suspend the project, it detailed its recommendations for how SCoPEx could proceed if researchers decide to revive the experiment.


The experiment, which sought to measure the behavior of aerosol plumes in the stratosphere, faced controversy over concerns that the development of geoengineering technology would tamper with the atmosphere in an unprecedented, and potentially dangerous, manner.

SCoPEx was confronted with further criticism, including from youth climate activist Greta Thunberg, after Keutsch planned a test flight in June 2021 to release a high-altitude balloon over Kiruna, Sweden.

The test was intended to be part of a planning process leading to the eventual launch of a balloon that would release a small number of particles into the stratosphere, allowing scientists to observe whether they could reflect sunlight back into space.

The planned test was halted after backlash in a 2021 letter from the Saami Council, an indigenous group representing the Saami people from Sweden and its surrounding countries.

In the letter, the council stated that the experiment’s plan to launch a balloon in Kiruna, Sweden would “constitute a real moral hazard” and that there are “no acceptable reasons for allowing the SCoPEx project to be conducted either in Sweden or elsewhere.

The Saami Council did not respond to a request for comment on Tuesday.

SCoPEx had its latest setback last year when Keith — one of the Harvard professors leading the project — left Cambridge for a faculty position at the University of Chicago, where he leads the Climate Systems Engineering initiative.

Keith said in an interview on Tuesday that critical news coverage and pressure from climate activists complicated SCoPEx’s ability to “move forward with the experiment.”

“I think it’s worth doing these experiments as the world considers whether or not to actually potentially use these technologies to reduce climate risks,” Keith added. “This experiment just became the focus of that conversation and got blown out of proportion.”

John H. Shaw, Harvard’s vice provost for research, and James H. Stock, vice provost for climate and sustainability, wrote in a joint letter on Monday that SCoPEx’s platform will be “repurposed for basic scientific research in the stratosphere unrelated to solar geoengineering.”

Shaw and Stock said that despite the end of the SCoPEx project, Harvard researchers will continue to explore solar geoengineering and carbon removal through the Salata Institute.

“Solar geoengineering research will continue at Harvard under the auspices of the Solar Geoengineering Research Program, which will explore the many dimensions of this issue, including the science and engineering, governance, and political and social implications,” Shaw and Stock added.

Keith also defended the general premise of the SCoPEx experiment, stating that it was not unsimilar to other experiments conducted by environmental scientists.

“People felt the experiment was a momentous step, although, in fact, it’s quite similar to other experiments that have been done,” Keith said. “There are many environmental experiments involved in releasing materials or deliberate perturbation to the environment.”

“Those are quite common in environmental science,” he added.

Keith also took aim at a “vocal minority” of scientists who have voiced concern that SCoPEx’s technology may provide an excuse to reduce pressure to cut emissions.

However, Keith stated that while he believed the concern to be legitimate, it was not an “ethical justification for not doing research.”

Keith compared his geoengineering research critics to skeptics of airbags who say their existence in cars encourages more dangerous driving.

“It may be true that people now drive in slightly more careless ways, because cars are safer,” he said. “But that’s not a bad thing.”

—Staff writer Elizabeth Peng can be reached at

—Staff writer Nicholas J. Frumkin can be reached at