A solar reflector for the Earth? Scientists explore potential risks and benefits

Nine of the hottest years in human history have occurred in the past decade. Without a major change in this climate trajectory, the future of life on Earth is in question. Should humans, whose fossil-fueled society is driving climate change, use technology to curb global warming?

Every month since September 2019, the Climate Intervention Biology Working Group, a team of internationally renowned experts in climate science and ecology, has met remotely to bring science to bear on this issue and the consequences of geography. -engineering a cooler Earth by reflecting part of the sun. radiation away from the planet – a climate response strategy known as solar radiation modification (SRM).

The group’s founding article, “The Potential Ecological Impacts of Climate Intervention by Reflecting Sunlight to Cool the Earth,” was published in the latest Proceedings of the National Academy of Sciences (PNAS).

“Being part of this working group has been quite eye-opening for me,” said co-author Peter Groffman, an ecosystem ecologist at the Center for Advanced Scientific Research at the Graduate Center, CUNY and the Cary Institute of Ecosystem Studies. “I didn’t realize that modeling climate intervention was so advanced, and I think climate modellers were unaware of the complexity of the ecological systems affected. It is a strong reminder of the importance of the need for a multidisciplinary analysis of complex problems in environmental science. “

The interdisciplinary team is co-led by Phoebe Zarnetske, community ecologist and associate professor in the Department of Integrative Biology and Ecology, Evolution and Behavior Program at Michigan State University, and ecologist Jessica Gurevitch, Distinguished Professor in the Department of ecology and evolution of Stony. Brook University.

Conversations between Gurevitch and climatologist Alan Robock, distinguished professor in the Department of Environmental Sciences at Rutgers University, gave rise to the pioneering group, which is more aware than anyone that geoengineering the Earth’s atmosphere is more than just a science fiction scenario.

“There is a dearth of knowledge about the effects of climate intervention on ecology,” Zarnetske said. “As scientists, we need to understand and predict the positive and negative effects this could have on the natural world, identify the main knowledge gaps and start predicting the impacts this could have on terrestrial species and ecosystems. , marine and freshwater if that was the case. adopted in the future. “

The costs and technology required to return heat from the Sun into space are currently more accessible than other ideas for climate intervention such as carbon dioxide (CO₂) from the air. The working group anticipates that their lively discussions and open access article will encourage an explosion of scientific research into how a climate response strategy known as solar radiation modification (SRM), in tandem with reducing greenhouse gas emissions, would affect the natural world.

The feasibility of SRM’s efforts on a planetary scale hinges on precise predictions of its myriad of results provided by the well-established computer simulations of the Geoengineering Model Intercomparison Project (GeoMIP). the PNAS The paper lays the groundwork for expanding GeoMIP’s reach to include the incredible range and diversity of Earth’s ecosystems.

“While climate models have become quite advanced in predicting the climate outcomes of various geoengineering scenarios, we have very little understanding of what the possible risks of these scenarios might be to species and natural systems,” Gurevitch explained. “Are the risks of extinction, changing communities of species and the need for organisms to migrate to survive under SRMs greater than those of climate change, or do SRMs reduce the risks caused by SRM? climate change?”

“Most GeoMIP models only simulate abiotic variables, but what about all living things that are affected by climate and depend on energy from the sun?” Zarnetske added. “We need to better understand the possible impacts of SRM on everything from soil microorganisms to monarch migrations to marine systems.”

Zarnetske’s Spatial and Community Ecology Lab (SpaCE Lab) specializes in predicting how ecological communities respond to climate change at all scales, from the microcosm to the global, which makes it uniquely positioned to help the work to illuminate vital data for future SRM scenarios such as stratospheric aerosol response (SAI), the subject of the paper.

SAI would reduce some of the incoming solar radiation by reflecting sunlight back into space, like what happens after large volcanic eruptions. Theoretically, it would be possible to continuously replenish the cloud and control its thickness and location to reach a desired target temperature.

But the article reveals the under-studied complexity of the cascading relationships between ecosystem function and climate in different SAI scenarios. In fact, they argue, climate change mitigation must continue regardless of whether the SRM is adopted, and the question remains whether one or more SRMs can be beneficial in addition to decarbonization efforts.

“Although the ISC can cool the Earth’s surface to a global temperature target, the cooling can be unevenly distributed, affecting many ecosystem functions and biodiversity,” Zarnetske said. “Precipitation and surface ultraviolet radiation would change, and the SAI would increase acid rain and not reduce ocean acidification.”

In other words, SRM is not a silver bullet for solving climate change. Until the task force’s efforts inspire new research into the effects of different climate response scenarios, SRM is more like shooting in the dark.

“We hope this document will generate much more attention on this issue and greater cooperation among scientists in the fields of climate science and ecology,” Gurevitch added.

The Climate Intervention Biology working group is funded by the National Science Foundation and will host sessions at two upcoming scientific conferences: “Biosphere Responses to Geoengineering” at the American Association for the Advancement of Science (AAAS) Annual Meeting this month here, and to The Ecological Society of America in August 2021.