Light clouds over the Pacific could cool temperatures in the western U.S.
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Cloud modification techniques could reduce temperatures in the western US but eventually lose their effectiveness and could push global heat waves towards Europe by 2050, a modelling study says.
There is growing interest in mitigating the severe effects of global warming using various geoengineering techniques, including marine cloud brightening (MCB), which aims to reflect more sunlight away from the Earth’s surface by seeding the lower atmosphere with sea-salt particles to form bright marine stratocumulus clouds.
Small-scale MCB experiments are already underway Australia’s Great Barrier Reef A similar effort is underway in San Francisco Bay, California, where proponents hope it could reduce the intensity of heatwaves in certain areas as the climate gets…
Katherine Rick Researchers at the University of California, San Diego (UCSD) and their colleagues modeled the impacts of a potential MCB program to cool the western United States under current climate conditions and projections for 2050.
The team modeled the impact of the MCB in two locations in the North Pacific, one in the temperate zone and one in the subtropics, applying the MCB for nine months each year for 30 years, essentially altering the long-term climate.
The researchers found that under current climate conditions, MCBs could reduce the relative risk of exposure to dangerous summer heat by up to 55 percent in parts of the western U.S. However, MCBs would dramatically reduce rainfall not only in the western U.S. but also in other parts of the world, such as the Sahel region of Africa.
They also modeled the impact of MCB in 2050 in a scenario projecting global warming of 2°C above pre-industrial temperatures. Under these conditions, the same MCB program would have been ineffective, causing dramatic warming across almost all of Europe except the Iberian Peninsula. The modeled temperature increases were particularly large in Scandinavia and central and eastern…
Jessica Wang The big takeaway, say the UCSD researchers, is that the impacts of regional MCBs are not always intuitive: “Our results provide an intriguing case study showing how a highly concentrated disturbance to a small part of the Earth can reveal unexpected complexities in the climate system through regional geoengineering.”
While previous MCB experiments in Australia and California were not large enough to cause detectable effects on the climate, they suggest that regional geoengineering may be closer to reality than previously thought, Wang said. “More regional geoengineering modeling studies like this one need to be conducted to characterize these unintended side effects before they occur in the real world.”
Another problem, Rick says, is that if countries start relying on these methods while they’re still effective, they could undermine efforts to reduce carbon emissions — and if geoengineering stops working, it could put the world on an even more dangerous trajectory, he says.
“Lock-in is a big concern people have about geoengineering approaches in general, because there are opportunity costs to pursuing these approaches,” Rick says. “In the kind of world we’re simulating, what other risk management approaches would we have invested in developing if we hadn’t pursued MCB?”
Daniel Harrison A researcher from Australia’s Southern Cross University is project leader of a study investigating whether MCBs could be used as a tool to mitigate heatwaves in the Great Barrier Reef region in the future.
He said the scenario modelled by the new paper’s authors was “completely unrealistic and extreme.” “This is a major shock to the Earth’s climate system, so of course there will be consequences,” he said.
Harrison says the project he’s studying would involve MCB in a much shorter time frame and in a much more localized area than the one modeled by Lick’s team.
John Moore Researchers from the University of Lapland in Finland say there is an urgent need for further research into solar geoengineering to more thoroughly explore possible outcomes, including the impacts on indigenous peoples in low-income countries and the Arctic.
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Source: www.newscientist.com
