「经济学人」Cool heads

It is supporting experiments to thicken sea ice and make clouds more reflective

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SOLAR GEOENGINEERING is a heated topic. The core idea is to deliberately interfere with the environment in order to cool the climate, thus averting the worst consequences of the unintentional interference caused by rampant fossil-fuel combustion. Most of the potential methods involve reflecting sunlight back into space, thereby stopping that energy being trapped in the atmosphere as heat. Those in favour of researching them point to their potential to cheaply and substantially reduce global temperatures. Critics, meanwhile, highlight the risk of altering weather systems and disrupting atmospheric chemistry (with global and ungovernable consequences) while distracting countries from the hard but necessary work of cutting carbon emissions.

In an attempt to provide some evidence, Britain’s Advanced Research and Invention Agency (ARIA), an independent funding organisation backed by public money, announced at the end of April that it would be providing £56.8m ($75.4m) to geoengineering projects. The funding will be disbursed over the next five years to 21 projects exploring various dimensions of the problem. That announcement is enough to make Britain the largest state funder of solar-geoengineering research. That represents nearly 40% of all solar geoengineering funding that SRM360, an educational non-profit, estimates was awarded up to the end of 2024.

ARIA is spending heavily in part because it is throwing a wide net. It wants  to “look holistically” across different technologies and approaches, to see if “they could ever be effective or scalable”, says Mark Symes, an electrochemist at the University of Glasgow and the programme’s director.

To that end, half of the cash is earmarked for five projects which propose to conduct outdoor experiments. One, in the Canadian Arctic, will look at deliberately thickening patches of sea ice to see if that helps it last through the summer season. Two others (one at a site on Australia’s Great Barrier Reef, another somewhere in Britain) will attempt to use fine sprays of seawater to increase the reflectivity of either the clouds or the atmosphere more broadly. Another experiment, also in Britain, will assess whether changing a cloud’s electric charge will affect its brightness. And the final experiment, to be conducted in either America or Britain, will see what happens when tiny amounts of reflective aerosols are exposed to the stratosphere.

Such experiments are a novelty: almost all previous proposals have been cancelled or put off due to public outcry. That means a lot of critical basic science has not been done, says Dr Symes. To minimise the chance of harmful consequences, ARIA has imposed strict limits on the scale of these experiments, including their geographic extent. All must also be subject to an environmental assessment and secure the agreement of nearby communities. An oversight committee will also provide ARIA with independent expert advice.

Of the other projects, roughly a quarter are aimed at answering questions either about the ethics of geoengineering or how it might be regulated. Another seven are dedicated to modelling efforts, and a further four aim to study the real-world processes that affect how sunlight is reflected to improve future monitoring. (One modelling project is being conducted by The Degrees Initiative, a non-profit chaired by a member of The Economist’s staff.)

Such projects should clarify whether geoengineering can ever be a viable option to avert dangerous climate tipping-points. But ARIA remains adamant that it is no silver bullet. “This is not a substitute for decarbonisation,” says Dr Symes. He believes that should remain the priority.

This article appeared in the Science & technology section of the print edition under the headline “Cool heads”

(May 15th 2025)

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