Scientists are debating if there is a way to stop Earth’s climate from changing or even help the planet cool down — and, if they can do such work, whether or not they should.
Offsetting the effect of greenhouse gas emissions is a complicated science called geoengineering. In ideas that have been proposed, experts would either have to remove carbon dioxide from the atmosphere, or tinker with the system so that more of the sun’s radiation reflects back into space or more heat can escape the Earth. But any effort to cool off the planet could have unintended consequences, assuming it is first performed accurately and effectively. Three separate articles just published in the journal Science focus on those concepts and concerns.
Scientists from the Carnegie Climate Geoengineering Governance Initiative warn in their article that the world will have to work together to choose a solution, rather than allowing a single person, country or small group of countries to make a choice and run with it. That could “further destabilize a world already going through rapid change” if something goes wrong.
But even in the case of the world’s leaders deciding upon a solution together, messing with the Earth’s climate is a risky business.
“In so doing, we may expose the world to other serious risks, known and unknown,” the authors say.
When it comes to removing carbon dioxide from the atmosphere, such work “would need to be implemented at very large scales to have the desired effect,” according to the scientists. That takes up a lot of land, which could put a squeeze on the agricultural industry, thus affecting food prices and availability. Such a method could also affect biodiversity.
Solar radiation management, the process through which scientists would change the amount of radiation reflecting back into space as opposed to reaching Earth, is no less perilous. The scientists foresee effects on the cycle through which water evaporates from the surface and returns as precipitation, changing rain patterns and doing nothing to slow down the acidification of the ocean.
“The world's most vulnerable people would likely be most affected,” they wrote.
Even if methods to decrease warming were successful, the writers also point out, Earth’s population would still need to work to reduce greenhouse gas emissions — the geoengineering simply would be buying us time to figure things out.
Some of those methods of buying time include changing the planet’s cloud coverage. In one perspective in Science, researchers investigate the pros, cons and nuances of thinning cirrus clouds to allow more heat to escape Earth. Those clouds specifically are not responsible for reflecting much of the sun’s radiation back into space, and serve more to trap heat coming off the surface below. Thinning out those clouds, therefore, could have a cooling effect. But it may negatively impact tropical climates.
“For the time being, cirrus cloud thinning should be viewed as a thought experiment that is helping to understand cirrus cloud–formation mechanisms,” the article says.
Another journal piece focuses on the details and implications of mimicking intense volcanic eruptions as a method to cool off Earth. Injecting aerosol particles of sulfur into the atmosphere would increase a protective layer that prevents heat from the sun from reaching the surface, instead reflecting it back into space.
“The effect is analogous to the observed lowering of temperatures after large volcanic eruptions,” the article says. And the process “could be seen as a last-resort option to reduce the severity of climate change effects such as heat waves, floods, droughts, and sea level rise.”
At the same time, however, it would reduce evaporation from the Earth’s surface, which would also reduce the amount of rainfall and could affect water availability.
No matter what option the world chooses — or doesn’t choose — the writers all call on leaders to start the discussion.
“The world is heading to an increasingly risky future and is unprepared to address the institutional and governance challenges posed by these technologies,” the scientists from the Carnegie Climate Geoengineering Governance Initiative say. “Geoengineering has planet-wide consequences and must therefore be discussed by national governments within intergovernmental institutions, including the United Nations.”