Scientists have presented a controversial plan to refreeze the North and South Poles and lower the global thermostat.
They say high-flying jets could spray microscopic aerosol particles into the atmosphere to reflect sunlight and cool melting ice caps.
About 175,000 flights per year would be required, releasing millions of tons of carbon dioxide.
But a former UK chief scientist has backed the plans, telling Sky News polar warming is now critical – and refreezing ice could curb global sea level rise.
The new study was led by Wake Smith of Yale University in the US.
He warned the plan would address an important symptom of climate change, not the cause.
“It’s aspirin, not penicillin. It’s not a substitute for decarbonization,” he said.
Under this plan, a fleet of 125 military air-to-air tankers would release a cloud of microscopic sulfur dioxide particles at an altitude of 43,000 feet (13 km) and a latitude of 60 degrees in both hemispheres, at roughly the equivalent of the Shetland Islands in the north and the Falklands in the south.
The particles would slowly drift poleward during high-altitude winds, slightly shading the Earth’s surface below.
Just over 13 million tonnes of particles released in spring and summer would be enough to cool the polar regions by 2°C, with more moderate cooling at mid-latitudes, according to research published in the scientific journal Environmental Research Communications.
Click to subscribe to ClimateCast wherever you get your podcasts
The plan is controversial, not least because the large number of flights – equivalent to more than two days of global air traffic in 2021 – would release greenhouse gases into the upper atmosphere where they are more damaging.
Other scientists are also cautious about triggering sunscreen, as it could have unintended consequences, such as reduced crop yields.
A plan to release particles from a balloon in northern Sweden last year was scrapped after protests from environmentalists. A full-scale release program would require international agreement.
Billionaire Patagonia founder donates company
But the researchers say only 1% of the human population lives in the target deployment area. And the £10billion-a-year cost of the scheme would be far less than carbon capture or other means of mitigating or adapting to climate change, they add.
“If the risk-benefit equation were to pay off anywhere, it would be at the poles,” Smith said.
“Any intentional rotation of the global thermostat would be of common interest to all of humanity.”
The poles are warming several times faster than the global average, with record heat waves reported in the Arctic and Antarctica earlier this year.
If the vast ice sheets of Greenland and West Antarctica reached a tipping point – now considered likely under current global warming projections – sea levels would rise by several meters.
Sir David King, former chief government scientist and founder of Cambridge University’s Center for Climate Repair (CCR), told Sky News that radical action was needed to save polar ice.
“We are here, right now,” he said.
“The idea is to save time while deeply and rapidly reducing greenhouse gas emissions.
“It is essential. If we continue to broadcast at the current rate, we are cooked.”
Dr Shaun Fitzgerald, director of the JRC, said the large number of flights could be justified if they addressed the immediate problem of sea level rise.
“Using planes is not pleasant at all, but the impact of these greenhouse gases is a longer term effect.
“We’re worried about the impacts (of climate change) right now. It’s really urgent.”
The JRC is working on a strategy in its laboratories to thin clouds over the Arctic Ocean with a fleet of ships pumping seawater into the atmosphere. The clouds would reflect sunlight back into space, cooling the ice in the region.
The CCR supports a UN moratorium on any form of large-scale geoengineering until experiments have shown it is safe and there is agreement on the critical need to use it.