Climate-engineering projects such as dimming the sun could do more harm than good, and funding should go elsewhere, experts have said.
In May, the UK government's Advanced Research and Invention Agency (Aria) announced £56.8m (€65.6m) for 21 "climate cooling" projects, which include looking into the logistics of building shade from the sun in space and injecting aerosols into the sky to reflect sunlight away from Earth.
However, a major new review - published in Frontiers in Science - has found that such projects are flawed, unfeasible and risk damaging the environment.
They said that the schemes distract from decarbonising, and research bodies should think twice before funding such ideas ahead of tested methods for lowering emissions.
Martin Siegert, a climate scientist at the University of Exeter, said: "I think some of these ideas have been given a disproportionately high amount of visibility compared with their maturity and their feasibility ... These ideas are often well-intentioned, but they're flawed."
The climate experts reviewed five proposed projects in polar regions, including pumping sunlight-reflecting particles into the atmosphere, installing 'sea curtains' to stop warm water reaching ice shelves, and fertilising the oceans to boost carbon-storing phytoplankton.
Valerie Masson-Delmotte, head of the Climate and Society Centre at Institut Pierre Simon Laplace, said: "[Aerosol injection experiments] could deplete ozone and could disrupt climate patterns, not just in polar regions, but at other latitudes.
"There could be large costs ... for instance, disruption of weather patterns, effects on energy production, effects on health or agriculture."
Expensive and impractical
Likewise, installing sea curtains in the Antarctic would not be feasible, because it would require travelling to remote and inhospitable regions, then anchoring the barriers into moving sediment thousands of feet below the surface.
An idea to drill down into ice sheets and suck water from beneath to stop them slipping into the ocean was also assessed by researchers and found to be expensive and impractical.
Plans to drop millions of glass microbeads into the ocean to reflect sunlight away from the planet and stop the water from warming were deemed risky, as the beads have been shown to be toxic.
Under plans by Aria, five outdoor field trials of climate cooling projects have been proposed, including shooting plumes of seawater spray into the sky to see if it can enhance the reflectivity of low-lying clouds.
Experiments will also be taking place in Canada to find out if it is possible to thicken Arctic sea ice.
The University of Reading has been given funding to research whether releasing electric charge into clouds could help increase their reflectivity and bounce back sunlight.
Commenting on the findings of the review, experts said it was still important to research geo-engineering solutions so there would be a fall back in the event of runaway climate change.