In 1991, a volcano in the Philippines erupted, shooting particles into the air that temporarily cooled the planet by reflecting solar energy. Now, facing the pressures of climate change, some scientists and activists believe we could mimic that process and deliberately alter the Earth’s natural systems through a method called solar geoengineering. But that might be a very dangerous idea.
A new paper in Nature Ecology & Evolution pokes a hole in the idea that solar geoengineering is a quick fix for global warming. If a nation or the planet as a whole embarks on a solar engineering project, which then stops abruptly because of lack of funds or intergovernmental conflict, it could backfire by putting a huge number of species at risk.
As global emissions continue to rise, scientists and activists alike have begun to debate more drastic interventions to mitigate the Earth’s warming, including solar geoengineering. The technology to achieve this artificially is still hypothetical—shooting a cloud of particles into the atmosphere has never been done—but it would be so cheap that conceivably one rogue government could do it.
“I would say it is a real possibility that somebody somewhere would pull the trigger,” Gernot Wagner, executive director of the Harvard Solar Geoengineering Research Program, told me over the phone.
In the new paper, Christopher Trisos, an ecologist at the National Socio-Environmental Synthesis Center, and his fellow authors sought to investigate what would happen to the biodiversity of our planet, or the number of different species within a given area, if we suddenly began injecting reflective aerosols into our atmosphere in 2020, and stopped abruptly in 2070.
“Nobody had done a global assessment of what the climate changes from geoengineering would mean for biodiversity and ecosystems,” Trisos told me over the phone.
Biodiversity is crucial for our own well-being, from fisheries production to the medicines we use, yet is threatened by climate change. Organisms must run or die in response to rising temperatures, and, even if they somehow survive, the dispersal can break ecosystems apart.
“Biodiversity underpins many aspects of human well-being,” Trisos said.
Trisos and his co-authors compared a geoengineering climate simulation in which aerosols are injected at one point in the equator beginning 2020 and ending abruptly in 2070 to a climate change model predicting temperature rise at its current pace. They found that the consequences for the world’s biodiversity would be far more dire than if we never geoengineered at all.
Let me paint a picture of what might happen to Earth’s biodiversity under this scenario, according to the research conducted by Trisos and his co-authors.
Emissions continue post-2020 even though we start pumping protective aerosols into the atmosphere. While temperatures also continue to rise, global warming is not as drastic as it would be in unmitigated climate change, according to these researchers.
Initially, organisms stop having to change habitats in response to rising temperatures. Highly mobile species that had already moved, like migratory birds, might return to their original ecosystems, and species that were too slow to move before, like corals, have a higher chance of survival than they did before the geoengineering project began. After mere decades, though, living things in highly biodiverse areas like the Amazon Basin have to start moving again, as much as they would have to in a non-geoengineering scenario.
Suddenly, it’s 2070. Governments begin to disagree on how to handle climate change, and, besides, they can no longer afford to pump aerosols into the atmosphere. As a result, we stop pumping aerosols into the atmosphere.
Then things really go to hell. The amount of warming that would have happened without geoengineering over fifty years is essentially squished into a decade.
All living things have to move four and six times faster than they do today, and around three times faster than they would in the non-geoengineering temperatures in 2070, to survive the heat. In tropical areas, which have the highest biodiversity, organisms would have to move at around 9.8 kilometers per year, or around 6 miles per year, which is far above the maximum speed the majority of organisms can move. This is especially bad for tropical species, which are less heat tolerant.
Animals have to move at these high speeds on over 90 percent of the Earth’s surface. Ecosystems start to fragment, a scenario in which the climate becomes so drastically different in an area that species must move in different directions to find suitable habitat. Imagine lions and zebras, both currently found in southern Africa, fleeing in different directions.
“In many cases, temperature would change in one direction and precipitation would change in another direction,” Alan Robock, a climate scientist based at Rutgers University and one of the co-authors, told me in a phone interview. Some habitats with specific temperatures and rainfalls would no longer exist. Once this happens, it’s pretty easy to imagine the whole ecosystem crumbling down.
This is as far as the research predicts, but we can imagine what might happen next: Species die off in mass extinctions, and, maybe, we die too.
This is just one scenario in a world of possibilities for what future Earth will look like. Still, it’s a cautionary tale for anyone who believes solar geoengineering is a quick fix. Trisos and his co-authors, who emphasize that a lot more research on solar geoengineering is needed, believe that emissions reduction is still the best option.
“The solution is to stop putting greenhouse gases into the atmosphere,” Robock said. “It’s really frustrating that’s not being done. We also know that it can be done: There’s enough Sun and wind to power the planet without using the atmosphere as a sewer.”
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