Cloud "engineering" could be more effective for climate cooling than previously thought, because of the increased cloud cover produced, new research shows.
In a study published in Nature Geoscience, researchers at the University of Birmingham found that marine cloud brightening （MCB）, also known as marine cloud engineering, works primarily by increasing the amount of cloud cover, accounting for 60%-90% of the cooling effect.
The practice of MCB has attracted much attention in recent years as a way of offsetting the global warming effects caused by humans and buying some time while the global economy decarbonises（脱碳）. It works by spraying tiny particles, or aerosols（气溶胶）, into the atmosphere where they mix with clouds and with the primary aim of increasing the amount of sunlight that clouds can reflect.
However, the ways in which MCB creates a cooling effect, and the ways in which clouds will respond to aerosols, are still poorly understood. To investigate the phenomenon, the researchers created a "natural experiment", using aerosol injection from the effusive eruption of Kilauea volcano in Hawaii to study the interactions between these natural aerosols, clouds, and climate.
Using machine learning and historic satellite and meteorological（气象学的） data, the team created a predictor to show how the cloud would behave during periods when the volcano was inactive. This predictor enabled them to identify clearly the impacts on the clouds that had been directly caused by the volcanic aerosols.
They were able to show that the cloud cover relatively increased by up to 50% during the periods of volcanic activity, producing a cooling effect of up to — 10 W/m² regionally.
Lead author, Dr Ying Chen, of the University of Birmingham, said, "Our findings show that marine cloud brightening could be more effective as a climate intervention than climate models have suggested previously. Of course, while it could be useful, MCB does not address the underlying causes of global warming from greenhouse gases produced by human activities. It should therefore be regarded as a ‘painkiller', rather than a solution."
