Controversial geoengineering projects to trial Earth-cooling tech funded by UK agency

The Advanced Research and Invention Agency is investing £57 million to study climate-manipulating technologies, but says it is taking a cautious approach

The United Kingdom’s high-risk research agency will fund £56.8 million (US$75 million) worth of projects in the controversial area of geoengineering — manipulating Earth’s environment to avert negative effects of climate change. The 21 projects include small-scale outdoor experiments that will attempt to thicken Arctic sea ice and to brighten clouds so that they reflect more sunlight. The hope is that successful technologies could one day contribute to efforts to prevent the planet from passing dangerous climate tipping points.

Supported by the Advanced Research and Invention Agency (ARIA) as part of its five-year Exploring Climate Cooling programme, the projects are among the most significant geoengineering experiments funded by a government.

The research has the potential to be beneficial, but must be undertaken cautiously, says Peter Frumhoff, a science-policy adviser at the Woodwell Climate Research Center in Falmouth, Massachusetts. “I am strongly supportive of responsible research on solar geoengineering and other climate interventions,” he says.

The funding package is the latest from ARIA, which was established in 2023 by the UK government and is modelled on the US Defense Advanced Research Projects Agency. With an £800-million budget, it funds high-risk, high-reward research into technologies that could have major consequences for humanity, including artificial intelligence and neurotechnology.

Divisive research

Another such area identified by ARIA was geoengineering, says Mark Symes, an electrochemist at the University of Glasgow, UK, who leads the Exploring Climate Cooling programme.

ARIA-funded experiments will investigate whether Earth’s diminishing ice sheets can be artificially thickened.Credit: Sean Gallup/Getty

Symes says the programme’s goal is not to find ways to replace more accepted approaches to tackling climate change, such as reducing carbon emissions. Instead, he says, geoengineering could be useful to prevent the world reaching certain tipping points that might occur before emissions reductions can have an effect. That could include “the collapse of circulations in the North Atlantic driven by the runaway melting of the Greenland ice sheet”, he says.

But even as climate change continues unabated, the concept is controversial: last year, researchers at Harvard University in Cambridge, Massachusetts, cancelled a project that would have introduced particles into the atmosphere in an effort to ‘dim’ the Sun after an outcry in Sweden, where the experiment was to take place.

Wary of such concerns, ARIA is taking a cautious approach. “We want to keep this research in the public domain,” says Piers Forster, a climate-change scientist at the University of Leeds, UK, who chairs a committee that will monitor ARIA’s climate-cooling projects. “We want it to be transparent for everyone.”

The 21 projects were selected through a competitive application process, which received about 120 proposals.

These fall into five research categories: studying ways to thicken ice sheets; assessing whether marine clouds could be brightened to offset damage to coral reefs; understanding how cirrus clouds warm the climate; looking at whether materials could be released into the stratosphere to reflect sunlight; and theoretical work on whether a sunshade deployed in space could cool portions of Earth’s surface.

Solar experiment

Five projects involve the most controversial area of geoengineering — outdoor experiments that interact with the environment. Frumhoff says that “building trust will be essential” in conducting such research. “I would be opposed to outdoor experiments being funded by any nation that isn’t aggressively and seriously reducing its own emissions,” he says.

A cloud-brightening trial will spray seawater particles over the Great Barrier Reef to make the clouds above it whiter and more reflective.Credit: Associate Professor Daniel Harrison/Southern Cross University

The stratospheric experiment — which is among the first outdoor solar-geoengineering experiment to receive government funding — will involve using balloons to carry materials such as limestone and dolomite dust into the stratosphere, to a height of about 15–50 kilometres, to see how they respond to the conditions. No particles will be released into the stratosphere, says ARIA.

Shaun Fitzgerald at the Centre for Climate Repair in Cambridge, UK, leads one of the ice projects. His team will conduct small-scale experiments in the Norwegian Arctic archipelago of Svalbard and in Canada to pump water from beneath ice sheets and spread it on top, covering up to one square kilometre in area, to see whether such a method could thicken Earth’s diminishing ice sheets.

“We’re going to see whether we’ve actually been able to grow more sea ice in the Arctic winter,” says Fitzgerald. Early results from work that Fitzgerald’s team did last year, before receiving ARIA funding, showed ice growth of “about half a metre”, he says.

Julienne Stroeve, a sea-ice researcher at University College London, isn’t sure how effective this method would be in preventing widespread sea-ice loss. “I do not think this is feasible at any real scale needed,” she says, noting that the impact on local ecosystems is also unclear. ARIA says that Fitzgerald’s experiment will be scaled up only if it is deemed to be “ecologically sound”.