To avoid the worst impacts of climate change, scientists have started researching the potential costs and benefits of solar geoengineering approaches that could reflect a small proportion of the Sun’s energy back into space and thus counteract some of the temperature rise caused by rising levels of atmospheric greenhouse gases. However, a new study looks at one such approach – injecting reflective particles into the atmosphere – and concludes that starting or stopping such geoengineering too quickly could, for a time, escalate the rate of climate change to unprecedented speeds, with catastrophic impacts on most groups of animals.
“We found that a rapid implementation or termination of geoengineering could accelerate climate change so much that most species would not be able to move fast enough to keep up with the changes,” said Chris Trisos, lead author and a postdoctoral fellow at the National Socio-Environmental Synthesis Center (SESYNC) at the University of Maryland.
Conducted by scientists from the SESYNC, Yale University, Stony Brook University, and Rutgers, this first of its kind research used data from climate simulation models to estimate how geoengineering could change the speeds at which rising temperatures move across the surface of the Earth, and how that could impact animals that need to migrate to track climate changes to survive. Their study was published January 22 in Nature Ecology and Evolution.
Trisos and his colleagues used data on how temperatures would change if a five-million-ton veil of sulphur dioxide was injected into the stratosphere annually from 2020 to 2070. That’s an annual amount equal to about one-quarter of the aerosols emitted by the Mount Pinatubo volcanic eruption in 1991, which cooled the earth by 0.5 degrees Celsius over two years.
The climate would cool immediately after such geoengineering started, as the climate system adjusted to less incoming solar radiation. However, the researchers caution about what would happen if society loses the will or means to continue injecting reflective aerosols into the atmosphere. A sudden termination of this geoengineering would cause rapid warming with changing temperatures projected to speed across the land at an average of 10 kilometers per year, three times faster than climate change without solar geoengineering. The fastest temperature velocities are projected to occur in tropical marine environments, where geoengineering termination could increase the speed animals need to migrate to stay in the temperature range of their natural habitat to more than 50 kilometers per year. This alarming pace could doom many slow-migrating tropical organisms, such as corals, plants, reptiles and amphibians, to extinction.
“If a solar geoengineering project gets terminated suddenly, for whatever reason, that could spell disaster for many animals and ecosystems,” said Trisos.
The researchers analyzed maps of biodiversity hotspots with their maps of temperature velocities to estimate the effects on different groups of animals including reptiles, birds, mammals, corals, and amphibians.
In response to existing climate change, birds, reptiles and mammals have already shifted their geographic ranges an average of 1.7 kilometers per year, but that is four to seven times slower than would be needed to escape warming from the termination of geoengineering.
“Some of the biggest climate shocks of termination would happen in the tropics, where biodiversity hotspots are concentrated,” Trisos said, “And amphibians, corals and fish would be the groups most harmed.”
Most animal taxa would take a major hit from high climate velocities. The study’s estimate of temperature velocities from geoengineering termination would outpace the average dispersal speed of 93 percent of mammal species in the Americas.
Trisos cautions that their estimate of rapid onset and termination of solar geoengineering may not be likely. “Hopefully any geoengineering project would start and end slowly,” Trisos said, “But it is possible that geopolitical divisions or turmoil might force sudden termination. And it’s important for us to understand the ecological impacts should such a scenario come to pass.”
“The list of potential unintended ecological consequences from geoengineering is long, and we’ve only just begun to scratch the surface of what might occur,” said Trisos.
Co-author Alan Robock, Distinguished Professor at Rutgers University, adds that even gradual implementation or termination pose multiple risks. “The solutions to global warming are to stop putting greenhouse gases into the atmosphere, and to adapt to the climate changes we cannot avoid. Trying to control the climate by creating a cloud in the upper atmosphere may be much riskier than not doing it, and our results quantify only one of the major risks to ecosystems as well as to people. While any sensible use of solar geoengineering would be done with gradual implementation and termination, it can never be guaranteed,” he said.