If started, geoengineering would be hazardous to stop

One way to limit global warming, in addition to reducing emissions of greenhouse gases, is geoengineering—altering the climate through approaches such as injecting sunlight-reflecting sulfur particles into Earth’s stratosphere. Once started, however, an abrupt end to stratospheric aerosol injection (SAI) could be catastrophic for biodiversity, suggests new research led by Christopher H. Trisos of the University of Maryland (Nat. Ecol. Evol. 2018, DOI: 10.1038/s41559-017-0431-0). Trisos and colleagues computationally modeled what would happen if SAI began in 2020 by injecting 5 teragrams of SO₂ per year, then maintained at that level until abruptly cutting off in 2070, perhaps because of a change in political will. The researchers observed mixed effects on biodiversity with implementation. Abrupt termination, however, would mean far faster climate change than most species would be able to adapt to. “Thus the adverse impacts of unsustained climate counteraction through SAI are likely to be around three times higher than the problem it is attempting to solve,” writes the University of East Anglia’s Phillip Williamson in a commentary that accompanies the paper.