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Volcanic ash from the Ejyafjallajokull eruption floats in the stratosphere. Photo: Andrew McMillan

[Update: Keith and Anderson released a statement yesterday saying that the original description of their plans by The Guardian was inaccurate. They write, "we have been and are currently exploring possible new strategies for interrogating the stratospheric system without affecting the background stratosphere in any quantitative way. To date, we have not written any proposal to actually do so. We want to be absolutely clear that that we have no plans to implement a geoengineering field study to release “thousands of tonnes of sun-reflecting chemical particles into the atmosphere to artificially cool the planet, using a balloon flying 80,000 feet over Fort Sumner, New Mexico.” ] 

The original post reads as follows:

According to Martin Lukacs writing in The Guardian, a team lead by engineers David Keith and James Anderson want to spray sunlight-reflecting sulfate particles into the upper atmosphere, a small-scale simulation of a volcanic eruption, to see if they can cool the climate. The experiment,

…will take place within a year and involve the release of tens or hundreds of kilograms of particles to measure the impacts on ozone chemistry, and to test ways to make sulphate aerosols the appropriate size. Since it is impossible to simulate the complexity of the stratosphere in a laboratory, Keith says the experiment will provide an opportunity to improve models of how the ozone layer could be altered by much larger-scale sulphate spraying.

“The objective is not to alter the climate, but simply to probe the processes at a micro scale,” said Keith. “The direct risk is very small.”

Environmental groups, and many scientists, are wary of a big push into geoengineering. Reporting for Wired UK, Joel Winston says that similar proposed technologies could, “lead to adverse effects on the Earth’s climate, including a reduction in global rainfall.”

That work, however, was conducted using a complex computer simulation of the Earth’s climate. Some scientists think that the models, despite their skill and complexity, may not be able to perfectly represent the effects of poking the system with a geoengineering stick. Winston says,

To understand different components of the Earth’s systems, Schmidt agrees that a few experiments are necessary. “I’m not generally against small-scale field experiments if they help us understand processes in nature,” says Schmidt. “But they should obviously be benign, and we should be very careful.” However, small-scale field tests are also limited, Schmidt believes, with climate simulations possibly being the only way to fully grasp the long-term and large-scale climate effects of geoengineering.

The Harvard researchers’ plan would not be the first foray in experimenting with geoengineering. There have been small trials that seeded the ocean’s surface with iron, a nutrient that can increase the population of small marine organisms that pull carbon dioxide from the atmosphere as they grow.

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