A geoengineering technique designed to lower high temperatures in California could inadvertently intensify heat waves in Europe, according to a study modeling the unintended consequences of regional tinkering with a changing climate.
The article shows that targeted interventions to reduce temperatures in a given area for one season may provide temporary benefits for some population groups, but this must be weighed against potential negative side effects in other parts of the world and the changing degree of effectiveness in over time.
The study authors said the findings were “frightening” because the world has few or no regulations to prevent regional applications of the technique, marine cloud lighting, which involves spraying reflective aerosols (usually in the form of sea salt or sea spray). ) in stratocumulus clouds over the ocean to reflect more solar radiation back into space.
Experts have said the lack of controls means there is little to stop individual countries, cities, companies or even wealthy individuals from changing their local climate, even if this is at the expense of people living elsewhere, potentially leading to competition and conflicts over climate change. interventions.
The recent sharp increase in global temperatures has prompted some research institutions and private organizations to engage in previously virtually taboo geoengineering research.
In Australia, scientists have been testing marine cloud-lighting strategies for at least four years in an effort to cool the Great Barrier Reef and slow its bleaching.
Earlier this year, scientists from the University of Washington spotted sea salt particles over the flight deck of a decommissioned aircraft carrier, the USS Hornet, docked at Alameda in San Francisco Bay. This experiment was halted by the local government to assess 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 will be much more far-reaching and harder to predict. The authors, published Friday in Nature Climate Change, claim to be the first to show that the brightening effects of clouds could diminish or reverse as climate conditions change due to the already dramatic human impacts of burning fossil fuels and forests .
Using computer Earth system models of the climate in 2010 and 2050, they simulated the impact of two cloud-brightening operations conducted in different regions of the northeastern Pacific Ocean, one in the subtropics near California and one in the mid-latitudes near Alaska. . Both are designed to reduce the risk of extreme heat in the target region, the west coast of the US.
Counterintuitively, the longer-range operation had the greater impact because it used “teleconnections,” links in the climate system between geographically remote parts of the world.
The 2010 simulation suggested that the operation near Alaska would reduce the risk of dangerous heat exposure in the target region by 55% – equivalent to 22 million human days per summer – while the closer subtropical test saw a smaller but still significant gain of 16% would yield.
However, in simulations of the more perturbed 2050 climate, the same two operations produced very different results, as there were fewer clouds, higher base temperatures and a slowdown of the Atlantic Meridional Overturning Circulation (Amoc). Under these mid-century conditions, the operation near Alaska would have a drastically reduced effect on relieving heat stress in the western US, while the subtropical operation would increase temperatures – the opposite of the desired outcome.
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Impacts outside the target regions were also significantly different between 2010 and 2050. Previously, the simulations suggested that Europe would also be cooled by brightening marine clouds in the North Pacific. However, by 2050, local cooling would increase heat stress around the world, especially in Europe, due to Amoc’s slowdown.
“Our study is very specific,” says Jessica Wan, who is part of the research team led by UC San Diego’s Scripps Institution of Oceanography. “It shows that brightening marine clouds can be very effective off the US west coast if done now, but may not be effective there in the future and could cause heat waves in Europe.”
She said the results should concern policymakers and prompt them to establish governance structures and transparency guidelines not only at the global level, but also at the regional level.
“There’s really no governance in solar geoengineering right now. That’s creepy. Science and policy must be developed together,” she said. “We don’t want to find ourselves 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 heat waves.”