Climate change threatens public health, food security, water availability, and national security – just to name a few areas of impact. Dramatic reductions in emissions and increased investments in measures to adapt to unavoidable impacts are essential but may not be enough to limit severe climate risks—and to date, these actions have fallen far short of what is needed. Some researchers are proposing to do experiments to also test the potential feasibility and effectiveness of geoengineering approaches to help limit climate change, while recognizing that mitigation and adaptation must remain our first-line solutions.
What is solar geoengineering?
Geoengineering is an intentional large-scale intervention in the Earth’s climate system to counter climate change. Within that larger category, solar geoengineering describes a set of approaches to reflect sunlight to cool the planet. These might include injecting aerosols into the upper atmosphere as well as brightening clouds over the ocean. Injecting aerosols simulates what happens during volcanic eruptions, where volcanoes emit small particles that reflect sunlight and lead to cooling when they reach the atmosphere. Cloud brightening would use sea salt to stimulate cloud formation over the ocean to also help reflect sunlight.
While solar geoengineering could limit some harmful climate impacts, it could also have adverse impacts and would not address the root cause of climate change: rising emissions of heat-trapping gases from burning fossil fuels – or some of the resulting impacts, such as ocean acidification. We also know very little about how it could impact regional weather patterns, global politics, and efforts to curb global warming emissions. The National Academies authored a report in 2015 to assess the impacts, risks, and costs of different solar geoengineering approaches.
These immense risks around solar geoengineering prompt major scientific, ethical, and governance questions: The IPCC Special Report on 1.5 degrees stated that “even in the uncertain case that some of the most adverse side effects…can be avoided, governance issues, ethical implications, public resistance and impacts on sustainable development could render [solar geoengineering] economically, socially and institutionally infeasible.” To examine these questions more closely, the National Academies recently announced the launch of a new report to assess research priorities and research governance approaches around solar geoengineering.
Should solar geoengineering experiments proceed and, if so, under what conditions?
The Union of Concerned Scientists is now taking a hard look at whether and under what conditions outdoor experiments in solar geoengineering should go forward.
This is especially important as a group of researchers at Harvard University are proposing to conduct the first known stratospheric experiment. The Stratospheric Controlled Perturbation Experiment (SCoPEx) is a small-scale experiment proposed to take place in the Southwest United States in which a balloon would disperse about a kilogram of calcium carbonate aerosols in the atmosphere that researchers would monitor. While small in scale, the precedent SCoPEx would set is an extremely important one. What will governance look like for future experiments? Who gets to participate in the decision-making process? Would this lead to larger and perhaps riskier outdoor experiments?
Injecting aerosols into the stratosphere has regional and global implications, which makes outdoor experimentation a difficult subject to address. Its transboundary nature makes the line between small- and large-scale research a murky but critical one, necessitating different approaches and responses. UCS issued a position statement in February 2019 that states opposition to large-scale testing due to the potential global risks, and we outline key pre-conditions that must be met before small-scale experiments are undertaken to ensure that these efforts are done safely and transparently.
Governance & engagement
A fundamental aspect of decision-making around research is that there should be substantial leadership from nations and communities most vulnerable to climate change. Those most vulnerable should have a meaningful voice not only in decision making, but also in helping to shape research priorities. Diverse views prompt questions and ideas that discussions largely confined to select spaces in the global north cannot presume to know.
Additionally, researchers should support independent governance mechanisms for such research projects and accept funding only from entities and governments that also unequivocally support mitigation and adaptation measures to address the root of the climate change problem. Significantly, UCS Director of Science and Policy Peter Frumhoff helped establish and shaped the role for an independent advisory committee for SCoPEx. The committee, if it functions as intended, will ensure transparency and inclusion as well assess the risks around the experiment before a decision is made on whether or not it will take place. The process of this committee will be an important one to follow once it begins its work.
The future landscape
Given uncertainties and risks around it, solar geoengineering is deeply problematic. Some are opposed to experiments such as SCoPEx out of concern that it will legitimize solar geoengineering and give the United States and other nations, as well as fossil fuel companies, the incentive to keep emitting global warming gases unabated. These are valid fears.
Mitigation and adaptation are and must remain unquestionably the first-line solutions to climate change. However, it is becoming increasingly clear that our failure to take strong action to date means that the risks we face from climate change may not be limited by reducing emissions alone. We will have to invest aggressively in adaptation measures. And we must also develop an understanding of the potential feasibility and risks associated with solar geoengineering, should those become seriously considered or be employed by other actors. At such a moment, the scientific and societal understanding of the positive and negative consequences of regional or global deployment must be robust to inform such considerations.
As we state in our position statement, “A precautionary approach to grave climate risks is one in which society invests in developing a careful understanding of all possible climate response options, including ones that themselves pose substantial risks and uncertainties.”
Read the full UCS position on solar geoengineering here.