Imagine the world tried geoengineering, and imagine it worked. For 50 years we manage to keep the planet at its current temperature, sea levels stabilize, endangered species rebuild, and all this while we're still burning fossil fuels at a leisurely pace.

Then China is hit by a freak, devastating drought, and India is hammered by severe flooding. They blame the geoengineering experiment for disrupting global rainfall cycles and demand its immediate termination. World leaders oblige.

What happens next?

According to a recent study, the consequences of such a scenario could be even more devastating than not trying geoengineering in the first place.

The report from an international team of researchers used 12 models to determine what might happen if the planet used so-called solar radiation management (SRM) or atmospheric shading by injecting water vapor or sulfates into the atmosphere to offset 1 percent annual increases in CO2 concentrations for 50 years, then abruptly stopped the experiment.

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.

No time to adapt
In terms of adaptation, the rate of climate change might be more important than how much the climate changes, said Alan Robock, a climate scientist at Rutgers University who ran some of the models for the study.

"The ability of ecosystems to respond can be compromised if the changes are too rapid," the authors wrote in the study.

And for animals attuned to particular environments, the consequences could be particularly extreme, Robock said.

He cited several studies showing that a large number of species on the planet would become extinct in a "business as usual" global warming scenario. And in the geoengineering scenario they modeled, "we would get rapid climate change at a rate much faster than with global warming."

The study found the SRM experiment itself would cause problems.

Previous studies have modeled that geoengineering experiments could disrupt precipitation patterns around the world (ClimateWire, Nov. 6). The findings of this study only reinforce that theory, Robock said.

"Ones that keep temperature from changing reduce precipitation, and ones that keep precipitation from changing don't reduce the temperature," he said.

Hope for a 'controlled' suspension
All these potential dangers raise the question: Might it be safer to not try geoengineering at all?

Geoengineering comes with an encyclopedia of moral, ethical and legal questions. And although our current rate of global warming worries many scientists, it's also a warming we know a lot more about, can adapt to reasonably well and can predict with reasonable accuracy.

Right now, according to Ben Kravitz of the Pacific Northwest National Laboratory, who also helped run some of the study's models, very little is known about geoengineering. Scientists don't yet know an SRM experiment that would actually work, for example, let alone what some of the secondary effects of such an experiment would be.

"Right now, in my opinion, there's no evidence that geoengineering is less risky than global warming," Robock said.

"If you could control it, you could gradually stop it and reduce the rate of emissions gradually over a decade or two; that would make the climate changes smaller while you were doing it," he added. "But that assumes that it could be controlled and it would all be done rationally. It might be much more rational to not do it in the first place."

The authors said one of the main messages to take from the study is that, if we ever do try geoengineering, don't suddenly stop doing it one day.

Both Haywood and Robock suggested a gradual winding down of the geoengineering experiment if it must end, but the planet might not have that luxury, Kravitz said.

Whether it's that governments run out of sulfates to throw into the air, that the technology used to carry out the experiment breaks down beyond repair, or that countries suddenly lose the geopolitical will for it, the experiment could come to a shuddering, perilous halt whether we want it to or not.

In the paper, the authors wrote that "the expectation that humankind would be able to continuously maintain a geoengineering effort at the required level for this length of time is questionable, to say the least."

Ultimately, the authors echoed the popular sentiment that geoengineering should not be viewed as a "cure" for climate change.

"If we were to go out and do geoengineering and do nothing about CO2 emissions, that makes it more and more difficult to stop, and we'd need to do more and more geoengineering to keep up," Kravitz said.

"I wouldn't call that a sustainable solution."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500