A recent study reveals that geoengineering efforts to reduce high temperatures in California could inadvertently exacerbate European heatwaves.
Marine cloud brightening is a geoengineering technique that could have unforeseen global effects. It chills particular locations by spraying reflective particles into stratocumulus clouds. A study published in Nature Climate Change suggests that while actions to reduce temperatures in one area may provide short-term respite, they may also have long-term detrimental effects and varied successful outcomes.
Since no international laws prohibit the regional use of marine cloud brightening, the study’s authors referred to the findings as “scary.” “It shows that marine cloud brightening can be very effective for the US west coast if done now, but it may be ineffective there in the future and could cause heatwaves in Europe,” said Jessica Wan from UC San Diego’s Scripps Institution of Oceanography.
Without regulations, various countries, towns, businesses, or even wealthy people might change their local climates, sometimes to the disadvantage of others. This could cause rivalry and conflict over these interventions.
The recent surge in global temperatures has driven some research institutions and private organizations to explore geoengineering, a field that was once considered taboo. Scientists have been testing marine cloud brightening in Australia to cool the Great Barrier Reef and mitigate coral bleaching. Earlier this year, the University of Washington experimented by spraying sea-salt particles from a decommissioned aircraft carrier in San Francisco Bay, which was halted by local authorities to assess potential health risks.
The study employed Earth system computer models to simulate the impacts of marine cloud brightening in 2010 and 2050. Two operations were tested, one near California and one near Alaska, to reduce extreme heat on the US West Coast. Surprisingly, the more distant Alaska operation had a more significant impact due to “teleconnections,” which are climate links between distant regions.
In the 2010 simulation, the Alaska operation reduced dangerous heat exposure by 55% (equivalent to 22 million people-days per summer), while the subtropical test near California resulted in a 16% reduction. However, in the 2050 simulation, with fewer clouds and higher base temperatures, the Alaska operation’s effectiveness drastically decreased, and the subtropical operation near California increased local temperatures.
The effects beyond the target regions were also different between 2010 and 2050. Initially, the simulations suggested that Europe would benefit from the Alaska operation’s cooling effects. By 2050, however, the same operation could increase heat stress globally, especially in Europe, due to the slowing of the Atlantic meridional overturning circulation (Amoc).
Wan underlined how urgently governments need to set up rules for transparency and governance around solar geoengineering.
“There is no solar geoengineering governance right now. That is scary. Science and policy need to be developed together,” she said. “We don’t want to be in a situation where one region is forced to do geoengineering to combat what another part of the world has done to respond to droughts and heatwaves.”