Controversial geoengineering proposals would cause IRREVERSIBLE damage in Antarctica, experts warn – so, from ‘dimming the sun’ to ‘sea curtains’, what are the most divisive plans being floated?

A team of more than 40 scientists are sounding the alarm bell over risky geoengineering projects being considered at the north and south poles.

In a new paper, the global team of experts warn that concepts such as ‘dimming the sun’ and ‘sea curtains’ risk irreversible damage to these fragile icy environments.

The madcap ideas – which are being proposed by other researchers in the field – come at a high cost, are not feasible, and could even have dangerous knock-on effects, they say.

Geoengineering is the large-scale manipulation of environmental processes that affect Earth’s climate, in an attempt to halt global warming.

There are geoengineering projects in various stages of progress all around the world, not just the polar regions.

But the ones being considered at the Arctic and Antarctica are particularly worrying because they are such ‘pristine’ and ‘little-understood’ environments.

‘These ideas are often well-intentioned, but they‘re flawed,’ said lead author Professor Martin Siegert at the University of Exeter. ‘Deploying any of these polar projects is likely to work against the polar regions and planet.’

From ‘dimming the sun’ to ‘sea curtains’, ‘glass beads’ and ‘ocean fertilization’, here are six of the most divisive plans being floated.

DIMMING THE SUN

Officially known as stratospheric aerosol injection, dimming the sun is one of the most famous and controversial geoengineering ideas of all.

Typically, stratospheric aerosol injection (SAI) involves the release of tiny sulfur dioxide (SO2) particles into the stratosphere by planes to reflect sunlight.

Once injected into the stratosphere, sulfur dioxide forms sunlight-reflecting sulfate aerosols, said to have a cooling effect similar to that of a major volcanic eruption.

However, in high levels, sulfur dioxide can cause nausea, vomiting, stomach pain and corrosive damage to the airways and lungs.

The team also warn that SAI in polar regions will not be possible year-round, due to winter darkness, and ‘may have unwanted and unintended consequences’, such as air pollution.

Dispensing the aerosols, meanwhile, would necessitate balloons, airships, and even artillery, which would all come at a high cost.

Scientists at Yale University in Connecticut have already proposed SAI at the north and south poles to reverse ice loss and prevent the planet from crossing ‘dangerous temperature thresholds’. 

STRATOSPHERIC AEROSOL INJECTION: The technique involves the release of tiny sulfur dioxide (SO2) particles into the stratosphere by planes to reflect sunlight

Stratospheric aerosol injection is where tiny particles, typically sulfur dioxide (SO2), are released into the stratosphere by planes to reflect sunlight (AI-generated depiction)

In March 2023, it was revealed scientists had conducted two open-air experiments to test solar radiation management – reflecting sunlight away from the Earth.

SEA CURTAINS

A lesser-known but equally as farfetched polar geoengineering project already proposed by some scientists is known as ‘sea curtains’.

Sea curtains are gigantic artificial structures which would be inserted underwater to stop warmer water from rising up towards the ice shelves above.

Sea curtains in the Artic and Antarctica would therefore stop the ice shelves from melting and reduce the threat of rising sea levels, advocates claim.

Aside from the installation of such an object being ‘extremely challenging’, the sea curtain’s size may even exceed the capacity of ships to transport it, the study authors argue.

The curtain itself could affect water circulation in negative ways, such as impacting the delivery of nutrients for underwater life, while also polluting the water, depending on what it’s made from.

‘The installation of sea curtain structures is likely to have far-reaching detrimental marine environmental consequences,’ the team write.

SEA CURTAINS: These gigantic artificial structures would be inserted underwater to stop warmer water from rising up towards the ice shelves above. This, proponents claim, would stop the ice shelves from melting and reduce the threat of rising sea levels

GLASS BEADS

Antarctic and Arctic sea ice is important because the whiteness of the ice reflects the sun’s light, helping to keep the regions cool, known as a higher ‘albedo’.

Without this ice cover, dark patches of ocean are exposed instead, which absorbs sunlight rather than reflecting it – in turn, accelerating ice loss further.

As a potential solution, scientists have proposed scattering hollow glass beads over Arctic sea ice to increase its so-called ‘albedo’ (the amount of the light it reflects back).

However, the use of glass beads ‘raises significant concerns that must urgently be addressed’, the authors of this study warn.

For one, the beads could be mistaken for food by zooplankton, the microscopic marine algae near the bottom of the marine food chain.

Massive quantities of glass beads would be required – about 360 megatons annually, an amount equivalent to the annual global production of plastic.

Meanwhile, deploying them poses ‘significant logistical challenges and substantial emissions during production’, not to mention high costs.

GLASS BEADS: Scattering hollow glass beads over Arctic sea ice could make the overall surface more reflective, sending sunlight away and helping prevent global warming, some scientists claim

OCEAN FERTILIZATION

Another idea is ‘ocean fertilization’ – adding nutrients, most commonly iron, to the upper ocean to stimulate growth of microscopic organisms called phytoplankton.

Phytoplankton need key elements such as iron to grow, so the addition of iron in areas where they are depleted has been proposed to stimulate phytoplankton growth.

Crucially, phytoplankton also rely on carbon dioxide (CO2) for growth, which they’d have to draw from the surrounding air, thereby removing the greenhouse gas from the atmosphere, the theory goes.

However, altering the nutrient balance in the ocean like this could disrupt food webs and create ‘dead zones’ where oxygen levels are too low to support other organisms, the team say.

Also, some species of phytoplankton produce toxins that can harm marine life and even humans, as well as their pets.

What’s more, the areas treated with the nutrient would also need to be 10 times larger than the Southern Ocean to feasibly work.

As before, an ‘armada’ of specially-adapted ships would be needed to transfer and deposit the iron on ‘an ocean-wide scale’.

OCEAN FERTILIZATION: Dropping iron into the ocean stimulates phytoplankton growth, potentially enhancing atmospheric CO2 removal

Harmful algal blooms occur when phytoplankton rapidly increase or accumulate – leading to unsightly green patches (pictured) that are toxic to humans and pets

SEA ICE THICKENING

A slightly simpler idea, in theory, is ‘sea ice thickening’, where Arctic sea ice is artificially thickened to counteract sea ice loss.

It has been suggested that sea ice can be thickened by pumping seawater either onto the ice surface, where it will freeze, or into the air, where it will fall as snow onto the ice.

A prior study said sea ice could be thickened by about 3 feet (1 metre) using gigantic wind-powered pumps that spray seawater onto the ice surface.

But 10 million of these pumps would be needed to cover just 10 per cent of the Arctic Ocean, and 100 million to cover the entire Arctic.

Also, for it to be effective at all, the technique would have to be deployed ‘almost immediately’, which the team don’t think is possible.

‘Techniques to thicken sea ice would require a very large number of individual devices to be deployed onto the winter sea ice,’ they say.

‘It is unlikely to be logistically possible to operate at the scale necessary to make a significant difference.’

SEA ICE THICKENING: The idea here is to slow or reverse the decline of Arctic sea ice by artificially thickening it, by releasing seawater

SLOWING ICE

Lastly, slowing ice involves drilling down into ice sheets to increase friction at their very bottom – a drastic intervention akin to trepanning the human skull.

This, some researchers say, could reduce water pressure and the rate at which ice is discharged from ice sheets to the ocean, which contributes to global sea level rise.

But drilling activities could introduce contaminants below the surface and impact ‘delicate subglacial ecosystems and biodiversity’.

It would also require numerous drill holes scattered across the ice sheet – described as ‘a logistical feat unprecedented in polar fieldwork’.

This intervention strategy proposed for Antarctica is ‘scientifically flawed and likely to be logistically impossible’, they conclude.

Overall, the team say geoengineering projects at the poles trigger uncertainties regarding whether they’d work, substantial knowledge gaps regarding their cost-effectiveness, and a range of risks associated with deployment.

The obvious alternative to all these costly ideas, they stress, is ‘decarbonization’ – eliminating greenhouse gases in the atmosphere, which means stopping burning fossil fuels such as coal.

SLOWING ICE: This proposal involves drilling down into ice sheets to increase friction at the very bottom, reducing the rate at which ice is discharged from ice sheets to the ocean

They also warn of ‘termination shock’ – the rapid and severe warming that could occur if any future large-scale deployment of a geoengineering project were suddenly halted.

This could potentially occur if the apparatus involved broke or became faulty, or if scientists opted to switch to another method.

‘Earth’s climate [would have to] adjust abruptly to the conditions dictated by greenhouse gas concentrations, resulting in a swift, significant rise in global temperatures,’ they say.

Scientists commented on the proposals in a briefing ahead of the publication of their paper on Tuesday, in the journal Frontiers in Science.

WHAT ARE THE SIDE EFFECTS OF GEOENGINEERING STRATEGIES?

Scientists have proposed all sorts of solutions to fight climate change, including a number of controversial geoengineering strategies.

Among the many include: 

Afforestation: This technique would irrigate deserts, such as those in Australia and North Africa, to plant millions of trees that could absorb carbon dioxide.

Drawback: This vegetation would also draw in sunlight that the deserts currently reflect back into space, and so contribute to global warming.

Scientists have proposed all sorts of solutions to fight climate change. File photo

Artificial ocean upwelling: Engineers would use long pipes to pump cold, nutrient-rich water upward to cool ocean-surface waters.

Drawback: If this process ever stopped it could cause oceans to rebalance their heat levels and rapidly change the climate.

Ocean alkalinisation: This involves heaping lime into the ocean to chemically increase the absorption of carbon dioxide.

Drawback: Study suggests it will have of little use in reducing global temperatures.

Ocean iron fertilisation: The method involves dumping iron into the oceans to improve the growth of photosynthetic organisms that can absorb carbon dioxide.

Drawback: Study suggests it will have of little use in reducing global temperatures.

Solar radiation management: This would reduce the amount of sunlight Earth receives, by shooting reflective sulphate-based aerosols into the atmosphere.

Drawback: Carbon dioxide would still build up in the atmosphere.