Excerpt:

Harvard researchers have ceased a long-running effort to conduct a small geoengineering experiment in the stratosphere, following repeated delays and public criticism.

In a university statement released on March 18, Frank Keutsch, the principal investigator on the project, said he is “no longer pursuing the experiment.”

The basic concept behind solar geoengineering is that the world might be able to counteract global warming by spraying tiny particles in the atmosphere that could scatter sunlight.

The plan for the Harvard experiments was to launch a high-altitude balloon, equipped with propellers and sensors, that could release a few kilograms of calcium carbonate, sulfuric acid or other materials high above the planet. It would then turn around and fly through the plume to measure how widely the particles disperse, how much sunlight they reflect and other variables. The aircraft will now be repurposed for stratospheric research unrelated to solar geoengineering, according to the statement.

The vast majority of solar geoengineering research to date has been carried out in labs or computer models. The so-called stratospheric controlled perturbation experiment (SCoPEx) was expected to be the first such scientific effort conducted in the stratosphere. But it proved controversial from the start and, in the end, others may have beaten them across the line of deliberately releasing reflective materials into that layer of the atmosphere. (The stratosphere stretches from approximately 10 to 50 kilometers above the ground.)

...

Proponents of solar geoengineering research argue we should investigate the concept because it may significantly reduce the dangers of climate change. Further research could help scientists better understand the potential benefits, risks and tradeoffs between various approaches.

But critics argue that even studying the possibility of solar geoengineering eases the societal pressure to cut greenhouse gas emissions. They also fear such research could create a slippery slope that increases the odds that nations or rogue actors will one day deploy it, despite the possibility of dangerous side-effects, including decreasing precipitation and agricultural output in some parts of the world.

...