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Climate geoengineering technique ‘could devastate’ if stopped suddenly

Image credit: DT

Spraying sulphur dioxide into the upper atmosphere to form a cloud that cools the Earth has been proposed as a way to halt climate change, but if such a project was started it would need to be maintained, as a sudden cessation could have a devastating impact, US scientists have said.

The first study on the potential biological impacts of geoengineering by a team from Rutgers University has found that global impact on animals and plants could be dramatic.

The sulphur dioxide spray mimics the effects of a volcanic eruption and has been calculated to lower global temperature by about 1C, roughly reversing the amount of warming that had occurred since the start of the Industrial Revolution.

But if the operation had to stop suddenly for any reason the global impact could be disastrous, the new research suggests.

The US team conducted computer simulations of a scenario in which large-scale geoengineering is used to achieve a moderate level of climate cooling.

It involved aircraft spraying five million tonnes of sulphur dioxide into the upper atmosphere every year from 2020 to 2070.

They assumed that planes would spray 5 million tons of sulphur dioxide a year into the upper atmosphere at the Equator from 2020 to 2070. That’s the annual equivalent of about one quarter of the sulphur dioxide ejected during the 1991 eruption of Mount Pinatubo in the Philippines,  according to lead scientist Alan Robock.

The spraying would lead to an even distribution of sulphuric acid clouds in the Northern and Southern Hemispheres but a sudden halt to the spraying could lead to rapid warming – 10 times faster than if geoengineering had not been deployed, Robock said.

“Rapid warming after stopping geoengineering would be a huge threat to the natural environment and biodiversity,” he added.

“If geoengineering ever stopped abruptly, it would be devastating, so you would have to be sure that it could be stopped gradually, and it is easy to think of scenarios that would prevent that. Imagine large droughts or floods around the world that could be blamed on geoengineering, and demands that it stop. Can we ever risk that?”

Maintaining the sulphur dioxide cloud would mean aircraft having to fly continuously into the upper atmosphere; without continual spraying, it would last only about a year.

Many animals and plants would not be able to survive in a rapidly warming world, said the researchers, whose findings are reported in the journal Nature Ecology and Evolution.

“We really need to look in a lot more detail at the impact on specific organisms and how they might adapt if geoengineering stops suddenly,” Robock added.

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