With climate change threatening to cause devastating effects across the planet, nations have been struggling to control the human-generated greenhouse gas emissions that are driving the planet's warming trend. But the threat is so scary that some are advocating a more drastic stopgap solution. Geoengineering would involve a massive effort to alter Earth's natural systems and counteract the warming effect of our emissions, to give us more time to reduce them.
One idea that's gained attention is using aircraft to disperse large quantities of reflective particles high into Earth's atmosphere, which would block a portion of the sun's radiation from reaching Earth. As this Yale Environment 360 article describes it, solar geoengineering would mimic the effect of volcanic events such as the 1991 Mount Pinatubo eruption in the Philippines, which pumped 20 million tons (18 million metric tonnes) of sulfur into the upper atmosphere and actually caused global temperatures to drop by nearly 0.9 degrees Fahrenheit (0.5 degrees Celsius) in a single year.
One proposal described in the Environment 360 article would use Gulfstream jets to inject up to 1 million tons (0.9 million metric tonnes) of sulfur into the lower atmosphere each year, to counter about half of the warming effect from greenhouse gas emissions. The flights would continue for decades, and would only be phased out after efforts to control emissions stabilize the carbon dioxide concentration in the atmosphere.
A Disastrous Result
If such an effort proved successful, it might save life on Earth from being ravaged by the effects of rising temperatures. But a study published Jan. 22, 2018 in the journal Nature Ecology & Evolution shows that solar geoengineering also could go awry with disastrous results, if the effort was interrupted abruptly for some reason. If that happened, solar heating of the pent-up greenhouse emissions would cause temperatures to soar even more rapidly, so that animal and plant life would have difficulty moving to cooler latitudes to find habitats in which they could survive. (This University of Maryland press release also describes the research.)
"If you do geoengineering and it's terminated suddenly, it could be worse for ecosystems and biodiversity than if you just had climate change," the study's lead author, Christopher H. Trisos, explains. He's a postdoctoral fellow at the University of Maryland's National Socio-Environmental Synthesis Center.
In the scenario envisioned by the researchers, a massive global solar geoengineering project would begin in 2020, only to be stopped suddenly 50 years later. That might happen due to some violent global conflict, or because governments involved in the effort lost the political will to continue it. (President Donald J. Trump's decision to abruptly withdraw the U.S. from the Paris climate agreement last June provides evidence of how fragile international efforts can be.) Public opposition might also develop and force an end to such an effort.
If solar geoengineering, and its cooling effect, was terminated abruptly, the results could be disastrous. Trisos likens the situation to stopping water from coming out of a hose by plugging the opening with your thumb. If the amount of water flowing into the hose isn't reduced, the water simply will build up in the hose, so that when the thumb is removed, it comes rushing out.
Similarly, "If you stop the sulfur injection, you still have all those greenhouse gases that have built up in the atmosphere," Trisos explains. "So you get the warming in a shorter period."
Confronted with such fast-rising temperatures, living things would be under pressure to either adapt — probably not a realistic option, due to the speed of change — or else migrate to cooler places where their preferred habitat might still exist. In the northern hemisphere, that would mean fleeing northward. The researchers calculated that animals and plants would have to move north at a rate of 6.46 miles (10.4 kilometers) each year to escape warming. That's four times the recent temperature velocity on land due to climate change, and more than twice the future rate that would occur without solar geoengineering and with a moderate increase in emissions.
Not all species could keep up with that pace. "Insects seem most capable of surviving," Trisos says. "But amphibians and many mammals wouldn't be able to move that fast." Plants would have an even tougher time, he says.
No Easy Fix
The study bolsters the case that geoengineering would provide, at best, only part of the solution for climate change — a way to buy time, so that humans could wean civilization away from fossil fuels and stop pumping so much carbon dioxide into the atmosphere, and halt the warming effect that they've been causing. The authors note that the climate shocks caused by a sudden termination of geoengineering could be even larger or occur even more quickly if, in the meantime, countries don't make progress in cutting their carbon output, and instead continue at a "business-as-usual" rate.
"I'd say that the most effective thing we can do to address climate change is reduce greenhouse gas emissions," Trisos says. "If we ever were to do geoengineering, doing it without also doing significant greenhouse gas emissions reductions would be reckless."