As humans continue to burn fossil fuels and contribute to the warming of Earth’s atmosphere, researchers have begun to explore techniques to deliberately modify the climate so as to temporarily offset the worst impacts of climate change. A new paper co-authored by Indiana University professor Ben Kravitz continues the process of bringing that research from the lab into policy circles, describing the results of several geoengineering scenarios simulated on high-performance computers that fit possible timelines for potential widescale deployment.
The study, published in the Proceedings of the National Academy of Sciences, illustrates the complexities facing world leaders considering turning down the planet’s temperature through artificial means.
“The decision space is huge,” said Kravitz, a research affiliate with IU’s Environmental Resilience Institute. “But we feel it’s important to articulate what some realistic scenarios look like so people can talk about geoengineering in a more responsible way.”
Large-scale stratospheric aerosol injection, pumping large amounts of tiny sulfur droplets into the stratosphere to reflect sunlight into space, shows promise as a cost-effective way of temporarily offsetting the dangerous effects of high carbon dioxide levels in the atmosphere. The technique is far from a silver bullet, however, with models projecting aerosols would reduce global precipitation on average, potentially disrupting water access and agriculture. Furthermore, the technique must be applied continually until atmospheric CO2 levels reach a desirable concentration. Early termination would result in massive, rapid climate change that would be nearly impossible to adapt to.
To get a better idea of how geoengineering deployment might impact the planet, the researchers made use of SSP2-4.5, a model where emissions hover around current levels before beginning to fall by the middle of the century. The team then considered three different cooling amounts for geoengineering efforts: 1.5, 1 and 0.5 degrees Celsius. The models also pushed the start date of implementation to 2035 or 2045 to reflect a more realistic timeline.
By comparing model results, the research team identified several key differences in geoengineering environmental impacts, such as regional weather patterns and sea levels, that could guide decision making. To add further complexity, researchers compared the effects of imperfect implementation caused by, for example, complicated worldwide politics. Another possible wrinkle considered was the effects of an unforeseen climate-altering event, such as a volcanic eruption.
Previous analysis showed that, following a sudden stop in deployment, the cooling effects of aerosol release would dissipate in 15 years, a relatively short adaptation timeframe. The team found, however, that aerosol treatments could likely withstand brief interruptions without jeopardizing cooling. A 10-year phaseout was also shown to have similar effects as a sudden stop, suggesting that world governments seeking to avoid climate whiplash might need a much slower exit strategy, perhaps spanning decades.
“This shows the advantages and disadvantages of deciding how much to do,” Kravitz said. “Termination shock would be less risky if you’re doing less geoengineering.”
In future studies, Kravitz plans to model geoengineering efforts in greater detail, using a method he developed for downscaling climate models. He also wants to investigate how geoengineering might affect arctic sea-ice loss, permafrost thaw, acid-rain deposition, ozone loss, and more.
“Further study opens up the conversation about if we should use geoengineering,” he said. “Is this a good idea? The answer is, of course, it depends.”
