In a pro forma response to a congressional order, the Biden administration has issued a lukewarm report on the possibility of using solar geoengineering – reducing the amount of sunlight reaching the earth – to respond to global warming. The report — Congressionally Mandated Research Plan and an Initial Research Governance Framework Related to Solar Radiation Modification – advises, “The potential risks and benefits to human health and well-being associated with scenarios involving the use of SRM [solar radiation modification] need to be considered relative to the risks and benefits associated with plausible trajectories of ongoing climate change not involving SRM.”
Noting the skeptical tone of the White House report, Politico observed that “the White House said in a statement accompanying the report, ‘there are no plans underway to establish a comprehensive research program focused on solar radiation modification.’” The 2022 appropriations bill included the requirement for the geoengineering report.
Solar radiation modification, which has support for some climate scientists as a direct approach to reducing global temperature increase by limiting sunlight, is not a new idea, having been controversial for at least a decade. On prominent critic, former Clinton administration energy official and physicist Joe Romm, punning on the technologies for SRM, called it “smoke and mirrors.” A July 2014 POWER magazine article [which I wrote – Ed.] was headlined “Geoengineering: A Practical Climate Work-Around or Just Plain Crazy?” The article offered no answer to that question, nor does the White House report.
The basic concept is simple: block some of the sunlight reaching the earth. It’s not politics or economics, the conventional approach to dealing with a warming world, but engineering, hence “geoengineering.” Advocates for lowering the sunlight that hits the earth offer three approaches, obstruction, reflection, and thinning.
Obstruction involves adding sulfate aerosols into the atmosphere. Nature already does this, as in the massive eruption of Mt. Pinatubo in the Philippines in 1991. As described by NASA, “Because of the sunlight-absorbing effect of the aerosols in the stratosphere, scientists measured a drop in the average global temperature of about 1 degree F [0.6 degrees C] over the 15 months following the eruption.)”
The prime advocate of this approach to geoengineering is Harvard applied physicist David Keith. His 2013 book, A Case for Climate Engineering (MIT Press), makes a case that the little progress in reducing carbon emissions puts climate engineering on the table. He doesn’t offer solar modification as a panacea. He writes, “The bitter truth is that the world’s efforts to cut emissions have (with a few exceptions) amounted to a phony war of bold exhortation and symbolic action. It’s tempting to assert emissions cuts are impossible and that we must look to alternatives like geoengineering. This is double wrong. First, solar geoengineering may reduce risks in the short term but it cannot get us out of the long-term need to cut emissions. Second, to assert that emissions cannot be cut is to take human agency—and responsibility—out of the picture as if emissions were coming from some species other than our own.”
Stephen Salter, emeritus professor of engineering design at the University of Edinburgh, is the creator of the reflection approach to solar radiation modification (and also the founder of wave power). He has proposed mounting a fleet of ships to spray seawater to change the albedo of clouds. Albedo is the proportion of light reflected by a surface. Salter’s idea is to reflect sunlight coming to earth back into space, sometimes known as “marine cloud brightening.” Salter’s concept got early support from Microsoft founded and advanced energy technology funder Bill Gates.
A 2021 National Academies report calling for a U.S. government-supported research program on geoengineering described cloud brightening as “based on the idea of cooling Earth by increasing the reflectivity of low clouds over certain parts of the ocean. As an analogue, under the right conditions, the aerosol pollution from ships leaves behind a “ship track” caused by the emitted aerosols acting as additional cloud condensation nuclei. For the same total cloud water content, more droplets (from more nuclei) result in higher surface area and a more reflective cloud. It has been proposed that the same effect could be achieved by spraying a fine mist of salt water into the marine atmosphere.”
The third approach is cloud thinning. The National Academies report says, “Cirrus clouds—thin wispy clouds composed primarily of ice crystals that form in the upper troposphere—warm the planet (particularly at higher latitudes) because they reduce outgoing longwave radiation more than they reflect incoming sunlight. Reducing cirrus cover would thus produce a net cooling. It has been hypothesized that in the right conditions, it may be possible to seed cirrus with ice nuclei that would lead to fewer, larger ice crystals, with higher fall velocities, thus decreasing lifetime and hence cirrus cover.”
All three approaches to geoengineering have potential rewards and risks, which the White House report acknowledges. The report also says research on SRM should include “appropriate international cooperation.”
Perhaps the best advice comes from the late, legendary scientist Freeman Dyson (1923-2020) in his 1981 book Disturbing the Universe: “Science and technology, like all original creations of the human spirit, are unpredictable. If we had a reliable way to label our toys good and bad, it would be easy to regulate technology wisely. But we can rarely see far enough ahead to know which road leads to damnation. Whoever concerns himself with technology, either to push it forward or to stop it, is gambling with human lives.”
–Kennedy Maize