A geoengineering technique designed to reduce high temperatures in California could inadvertently intensify heat waves in Europe, according to a study that models the unintended consequences of regional tinkering with a changing climate.
The paper shows that targeted interventions to reduce temperatures in one area for one season can bring temporary benefits to some populations, but this needs to be weighed against potentially negative side effects in other parts of the world and the shift in effectiveness over time.
The study’s authors said the findings were “scary” because the world has little or no regulations to prevent regional use of the technique, marine cloud brightening, which involves spraying reflective aerosols (usually in the form of sea salt or sea spray). ) into stratocumulus clouds over the ocean to reflect more solar radiation back into space.
Experts said the lack of controls meant there was little to stop individual countries, cities, companies or even wealthy individuals trying to change their local climate, even if it was at the expense of people living elsewhere, which could lead to competition and conflict about interventions.
The recent sharp rise in global temperatures has prompted some research institutions and private organizations to engage in geoengineering research that was previously virtually taboo.
In Australia, scientists have been testing sea cloud brightening strategies for at least four years to try to cool the Great Barrier Reef and slow its bleaching.
Earlier this year, researchers at the University of Washington sprayed sea salt particles over the flight deck of the decommissioned USS Hornet aircraft carrier docked in Alameda, San Francisco Bay. That experiment was halted by the local government so they could evaluate whether the spray contained chemicals that could pose a health risk to people or animals in the Bay Area.
The new paper suggests that the consequences could be more far-reaching and harder to predict. The authors, published Friday in Nature Climate Change, say they are the first to demonstrate that cloud-brightening effects may be reduced or reversed as climate conditions change due to the already dramatic human impacts of burning fossil fuels and forests.
Using computer models of the Earth’s climate system in the years 2010 and 2050, they simulated the impacts of two cloud clearing operations conducted over different regions of the northeast Pacific Ocean, one in the subtropics near California and one in the mid-latitudes near Alaska. . Both were designed to reduce the risk of extreme heat in the target area, the US West Coast.
Counterintuitively, the more distant operation had more impact because it tapped into “teleconnectors,” links in the climate system between geographically distant parts of the world.
A 2010 simulation suggested that an operation near Alaska would reduce the risk of exposure to dangerous heat in the target area by 55%—equivalent to 22 million person-days per summer—while a closer subtropical test would produce smaller but still significant gains of 16%.
However, in simulations of a more perturbed climate in 2050, the same two operations produced very different results, as there were fewer clouds, higher core temperatures, and a slowing of the Atlantic meridional overturning circulation (Amoc). Under these mid-century conditions, operation near Alaska would have a drastically reduced effect on alleviating heat stress in the western US, while operation in the subtropics would push temperatures higher—the opposite of the desired result.
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Consequences outside the target areas were also significantly different between 2010 and 2050. Earlier simulations suggested that Europa would also be cooled by a brightening of the marine cloud in the North Pacific. However, by 2050, local cooling would increase heat stress worldwide, especially in Europe, due to the slowing of the Amoc.
“Our study is very specific,” said Jessica Wan, who is part of a research team led by the Scripps Institution of Oceanography at UC San Diego. “It shows that marine cloud brightening can be very effective for the US West Coast if done now, but may be ineffective there in the future and could cause heat waves in Europe.”
She said the results should concern policy makers and prompt them to create governance structures and guidelines for transparency, not only at the global level but also at the regional level.
“There really is no solar geoengineering administration at the moment.” This is scary. Science and politics need to be developed together,” she said. “We don’t want to be in a situation where one region is forced to geoengineer to combat what another part of the world has done to respond to droughts and heat waves.”