Solar Geoengineering Holds Promise for Addressing Climate Change

Stopping or reversing climate change can be achieved with significantly reduced side effects if solar radiation management efforts are optimized for the different seasons and latitudes, according to a new study by a team of researchers at Harvard University, the California Institute of Technology, and the Carnegie Institution for Science.

The study, which will be published in the November issue of Nature Climate Change, examines how tailoring radiative forcing, the change of the radiation balance of the Earth, can improve the efficiency of geoengineering—the use of large-scale interventions to moderate climate change. These interventions can range from carbon dioxide removal to iron fertilization of the oceans.

According to study co-author and Applied Physics Professor David Keith, solar engineering—putting aerosols in the stratosphere to reflect incoming sunlight back into space—is “the most credible idea in the near future.”

“In principle there is an infinite number of dimensions you could twist. You could control which season the radiative forcing is applied in,” said Keith. “You could have a layer of aerosol that is denser in the summer.”

The study showed that the melting of sea ice could be stopped with two to three times less radiative forcing if it is tuned specifically.

“People have done this crudely before, non-optimally, but this is first paper that tried to explicitly tune this effect. What we’ve shown is that we can tune it a lot,” Keith said.

The technology for solar geoengineering already exists, but countries must decide whether to implement it.

“[Solar geoengineering] is technically possible—whether that is a good thing to do or politically realistic is another thing,” said Keith. The biggest concern regarding the technology, he continued, is that people will cease trying to cut carbon dioxide emissions.

“The biggest risks are the unknown unknowns,” he continued. “There are lots of examples in history when interventions like this didn’t work out.”

According to Keith, it is physically impossible to stop or reverse warming in the article without geoengineering. Cutting emissions can only reduce the future contributions to global warming.

Countries hesitate to take action, however, because the effects of climate change are not uniform across the globe, and wealthy nations tend to be less vulnerable to the most deletrious results of global warming.

“We spend less than 1 percent of our GDP on agriculture so even if you double the cost [due to global warming] you’re hardly going to notice it,” he said.

Keith said he hopes that there will be serious efforts by all countries to cut emissions and to invest in geoengineering in an effort to help protect the natural world and the poorest nations.