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Cloud engineering in the US could cause heatwaves in Europe, new study shows

Low clouds gather over the Pacific ahead of forecasted rain in Los Angeles.
Low clouds gather over the Pacific ahead of forecasted rain in Los Angeles. Copyright AP Photo/Damian Dovarganes
Copyright AP Photo/Damian Dovarganes
By Rosie Frost
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Climate engineering manipulates the environment to try and avoid the worst consequences of climate change.


Cloud modifying techniques used to cool the climate in California could eventually push heatwaves towards Europe, according to a new study.

If global warming reaches 2C above pre-industrial by 2050, cloud modification could majorly warm almost all of Europe except the Iberian Peninsula. The research showed the biggest increases in Scandinavia, Central Europe and Eastern Europe.

The study’s authors say their findings are concerning because there are next to no regulations in place for this kind of local climate modification and the consequences could be hard to predict.

“Our study provides the first evidence that regional climate interventions that appear promising for climate risk management today might become ineffective as the climate continues to change,” says Kate Ricke, study co-author and part of the research team led by UC San Diego’s Scripps Institution of Oceanography.

“Remarkably, they could even end up increasing risk,” Ricke adds, because of the complexities of the climate system that we don’t have a perfect understanding of.

What is geoengineering?

Geoengineering manipulates the environment to try and offset some of the impacts of human-caused climate change.

It includes marine cloud brightening (MCB) where small reflective particles are added to clouds over the ocean to increase the amount of light they reflect. Small-scale MCB experiments have already happened in some parts of the world though they are sparse.

In 2020, Australia launched a government-funded programme to see if cloud brightening could mitigate the warming that causes coral bleaching in the Great Barrier Reef. Experiments have also taken place in California’s San Francisco Bay.

Although this research hasn’t been big enough to have any detectable effect on the climate, it does suggest that regional geoengineering could be a possibility in the near future.

A section of the Great Barrier Reef above Moore Reef in Gunggandji Sea Country off coast of Queensland in eastern Australia.
A section of the Great Barrier Reef above Moore Reef in Gunggandji Sea Country off coast of Queensland in eastern Australia.AP Photo/Sam McNeil

Geoengineering in a warming world

Scientists at the University of California, San Diego used simulations of the climate from 2010 and projections for 2050. By comparing these, they were able to show the impact an MCB project to cool the western US could have.

They used two locations in the northern Pacific Ocean, one in a temperate region near Alaska and another in a subtropical region near California - both intended to reduce the risk of extreme heat on the west coast of the US.

Under current climate conditions, the team found that MCB reduced the risk of extreme summer heat in parts of the western US by up to 55 per cent. But, it dramatically reduced rainfall both in this region and in other parts of the world like the Sahel of Africa.

The study’s authors say this would come as a result of the slowing of the Atlantic Meridional Overturning Circulation or AMOC - a global ocean conveyor belt that circulates water from north to south and back in a long cycle within the Atlantic Ocean.

More regulation is needed on climate engineering tech

Researchers say more consideration, governance, guidelines and policies are needed for this artificial climate control tech.

“We are still a long way out from any viable global implementation of solar geoengineering, but smaller scale interventions might become more attractive as the planet warms,” Jessica Wan, another member of the team behind the study.

She points out that the findings demonstrate what could happen “under a worst-case scenario” with an approach that works initially but fails due to climate conditions in the future.

“More work is needed to characterise these worst-case scenarios so we can be proactive, rather than reactive, to the consequences.”

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