Once we start geohacking, we won't be able to stop

Desperate times call for desperate measures, which is why geoengineering could save the world from the catastrophic effects of climate change. But a new study suggests that once we get started we won't be able to stop — and that a sudden halt to our geoengineering efforts could be worse than never doing it in the first place.

In a recent experiment, an international team of researchers used 12 models to figure out what would happen if we used solar management (SRM) or atmospheric shading by injecting water vapor or sulfates into the atmosphere. The model offset the 1% annual increase of CO2 concentrations over a period of 50 years.

But then the researchers abruptly stopped the experiment to see what would happen — and it wasn't good. Writing in Scientific American, Henry Gass explains:

They found that upon ending the experiment, the planet would experience a rapid increase in global mean temperature, along with increases in global mean precipitation rate and decreases in sea ice cover. In other words, all the global climate changes averted for 50 years thanks to SRM would be made up within five to 10 years.

These findings illustrate one way geoengineering could be "potentially hazardous," said Jim Haywood, a professor of atmospheric science at the University of Exeter and a lead author on the study. "Changes like temperature increases are very much accelerated if you stop the geoengineering mechanism," Haywood said.

The paper also found that warming would be faster in the Northern Hemisphere compared with the Southern Hemisphere, and that if geoengineering were used to suppress an even more dramatic warming scenario — say, 2 percent annual increases in CO2 concentrations — the rapid climate changes would be even faster after an abrupt suspension of the experiment.

Yikes. At the risk of stating the blazingly obvious, we had better think our geoengineering endeavors through before we put them into action. And if we ever try to geohack our atmosphere, we'd better not just pull the plug. A gradual disengagement would seem to be the right approach. But I can envision some future scenarios in which this might not be possible, like a large-scale war, global economic collapse, or a dramatic loss of faith in the plan.

Alternately, we could adopt a geoengineering scheme that won't result in climatic catastrophe if it were to suddenly be terminated. Or, we just avoid geohacking in the first place — but that, too, could lead to unhappy results.

Read the rest of Goss's article at SciAm. And read the entire study at Journal of Geophysical Research: Atmospheres: "The impact of abrupt suspension of solar radiation management (termination effect) in experiment G2 of the Geoengineering Model Intercomparison Project (GeoMIP)".

Image: UC Davis.