Climate scientists have long debated the potential risks and benefits of geoengineering techniques aimed at temporarily reducing global temperatures. A new study provides evidence that regional climate interventions could have far-reaching and unpredictable impacts across the globe.
The research, published in Nature Climate Change, used advanced climate models to simulate the effects of marine cloud brightening operations off the coast of California and Alaska. Marine cloud brightening involves spraying reflective aerosols like sea salt into low-lying clouds over the ocean to increase their reflectivity and cool temperatures below. While the technique showed promise for reducing extreme heat in western North America in current climate conditions, the models predicted very different outcomes by 2050.
In simulations of present-day conditions, marine cloud brightening near Alaska reduced dangerous heat exposure in the western US by 55%, equivalent to 22 million fewer person-days of extreme heat per summer. A similar operation off California provided a 16% reduction. However, when modeled for 2050 climate conditions, the Alaska operation had minimal cooling effect on the US, while the California operation actually increased emperatures, the opposite of the intended outcome.
Even more concerning were the projected impacts beyond the target region. While Europe initially benefited from cooler temperatures due to the North Pacific cloud brightening in current models, by 2050 the intervention was predicted to increase heat stress across Europe. The researchers attribute this to complex interactions with large-scale climate patterns like the Atlantic Meridional Overturning Circulation.
"Our study 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, one of the study's lead authors. She emphasized that the results demonstrate how regional climate interventions could have drastically different outcomes as baseline climate conditions shift over time.
The findings highlight the need for comprehensive modeling of geoengineering techniques under various future climate scenarios before any real-world testing or deployment. They also underscore concerns about the lack of international governance and regulation around climate intervention technologies.
Currently, there are few restrictions preventing individual nations, cities, or even private entities from experimenting with local climate modification, even if it negatively impacts other regions. This regulatory gap could potentially lead to conflicts between areas pursuing climate interventions for their own benefit at the expense of others.
Some climate engineering research is already underway, despite the risks. Scientists in Australia have been testing marine cloud brightening strategies to cool and protect the Great Barrier Reef from coral bleaching for several years. Earlier in 2024, researchers at the University of Washington conducted sea-salt spraying experiments from a decommissioned aircraft carrier in San Francisco Bay, though local officials halted the tests over environmental concerns.
As global temperatures continue to rise at an alarming rate, interest in geoengineering research that was once considered taboo is growing among both public and private institutions. However, this study serves as a stark warning that even well-intentioned climate interventions could have severe unintended consequences without careful modeling and international coordination.
The researchers stress the urgent need to develop scientific and policy frameworks around climate engineering in tandem. "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," Wan cautioned.
As climate change accelerates, the allure of technological fixes will likely grow stronger. But this study demonstrates that manipulating Earth's complex climate systems is fraught with risk and uncertainty. It underscores the continued importance of aggressive emissions reductions as the primary strategy for combating global warming, rather than relying on speculative geoengineering solutions.
