Aerosol geoengineering will not stop the Antarctic ice sheet from melting, simulations suggest

31 Aug 2023

Running out of time: geoengineering will not prevent the collapse of the West Antarctic Ice Sheet, study suggests. (Courtesy: Shutterstock Bernhard Staehli)

Artificially dimming the Sun by injecting aerosols into Earth’s atmosphere may help to delay a significant consequence of climate change in Antarctica, but not stop it — researchers in Switzerland and the UK have revealed. Through new simulations, a team led by Johannes Sutter at the University of Bern has showed that the collapse of the West Antarctic Ice Sheet (WAIS) can only be avoided if we eliminate global emissions of greenhouse gases as quickly as possible.

Climate scientists have been warning that global efforts to end our reliance on fossil fuels are not happening fast enough to avoid dangerous consequences for Earth’s climate in the coming centuries. Indeed, some scientists argue that the situation is so urgent that we should investigate geoengineering schemes for cooling the Earth.

“The window of opportunity to limit the global temperature increase to below two degrees is closing fast, so it is possible that technical measures to influence the climate will be seriously considered in the future,” says Sutter.

Reflecting sunlight

One potential type of geoengineering is solar radiation management (SRM). This would involve injecting aerosols into the stratosphere where it would reflect some incoming solar radiation back into space.

At first glance, SRM might appear to be a quick and easy fix. In particular, it could help us avoid reaching dangerous tipping points where feedback mechanisms such as the melting of polar ice would accelerate warming — and would be virtually impossible to reverse. However, many climate scientists predict that SRM would only have a limited success, and it could have dangerous consequences both environmental and political.

In their study, Sutter’s team investigated the potential for SRM to avoid one especially concerning tipping point: the collapse of the WAIS. Containing some 10% of all the ice covering Antarctica, some researchers estimate a collapse of the WAIS could trigger a sea level rise of 3–4 m if it melted entirely over the next few centuries.

Nearing a tipping point

As Sutter explains, “observations of ice flows in West Antarctica indicate that we are very close to this tipping point, and may have already passed it. With our study, we wanted to find out whether a collapse of the ice sheet could be prevented with SRM.”

To answer this question, the team combined ice sheet models with climate simulations. Up until the year 3000, they modelled the cooling effects of SRM in response to different emissions scenarios – ranging from an immediate, coordinated effort to eliminate greenhouse gas emissions globally, to a scenario where our emissions continue to rise unabated.

Our simulations show that the most effective way to prevent long-term collapse of the West Antarctic Ice Sheet is rapid decarbonizationJohannes Sutter

Their calculations revealed that if large-scale SRM is first deployed by the middle of this century, the WAIS collapse could be delayed by between 20–60 years under different emissions scenarios – but not avoided altogether. “Our simulations show that the most effective way to prevent long-term collapse of the West Antarctic Ice Sheet is rapid decarbonization,” says Sutter.

What is more, such a radical alteration to the atmosphere’s composition would come with substantial risks, and the possibility of unintended side effects. For example, SMR would only be successful if global-scale aerosol injection were maintained for centuries, until concentrations of greenhouse gases return to safe levels. If this stopped for any reason, global temperatures would rise sharply.READ MORE

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Altogether, the team’s results provide a robust case against the use of SRM to avoid tipping points like the WAIS collapse, and further emphasise the urgent need to eliminate global carbon emissions as quickly as possible.

“SRM would be another global experiment and a potentially dangerous human intervention in the climate system,” says Thomas Stocker, Sutter’s colleague at the University of Bern. “In any case, it should be prevented according to the UN Framework Convention on Climate Change.”

The research is described in Nature Climate Change.

Sam Jarman is a science writer based in the UK

FROM PHYSICSWORLD.COM    16/11/2023