Solar geoengineering: Spectacle, tragedy, or solution?

Solar geoengineering (SG), also known as solar radiation management, refers to a set of technologies designed to cool the planet by blocking intense sun rays and scattering incoming solar radiation away from the earth. Various SG approaches, such as marine cloud brightening, surface-albedo enhancement, and stratospheric sulfate aerosol injection (SAI) have been proposed, but SAI is the most researched approach. SG is gaining prominence as a potential solution to the worst global warming impacts, such as loss of sea ice and accelerated sea level rise. The Paris Agreement requires limiting the global average temperature well below 2°C to counter dangerous climate change. However, human influence has increased global surface temperature to about 1.3°C above pre-industrial levels. Unless the current trajectory is halted, global warming will surpass 1.5°C and cause a climate emergency, bringing abrupt and shockingly harmful impacts. The drastic failure of current mitigation strategies—and the absence of effective alternatives to minimize climate impacts—calls for new, extraordinary measures that work on short timescales. SG could prevent surface temperature rise and avoid adverse effects on natural ecosystems and society—protecting biodiversity and the world’s most vulnerable populations.  

In two studies, researchers at Aarhus University, University of Sussex Business School, Dublin City University, and Little Flower Seminary have assessed and summarized existing literature on geoengineering studies published over the last decade. The team has studied potential gains, drawbacks, research gaps, and effective policies for research and deployment of SG technology. Their research tells us that although SG has the potential to rapidly cool the atmosphere, this approach is contentious, bringing with it grave risks and great uncertainty that should be weighed before implementing the technology.  

In his research published in the journal of Energy Strategy Reviews, Dr. Benjamin Sovacool analyzes prior SG assessments and documents the SG’s potential benefits and risks. Sovacool defines SG, its technologies, and trends in research, development, and deployment through 2021. His study notes that SG has potential technical, financial, environmental, and political benefits. He also reveals that SG carries considerable risks that could outweigh benefits for the climate.  

According to Sovacool’s study, compared to other mitigation and adaptation approaches, SG options are highly feasible and can be deployed quickly: if properly invested, SG could rapidly cool the planet within a year. The study further states that SG costs are an order of magnitude smaller than those of other climate mitigation options. It would cost only $100 billion to implement a global SG program, compared to $1 trillion or more required to implement a single mitigation effort, such as a widescale shift toward nuclear energy. SG costs one-tenth of the cost of building fleets of nuclear power stations. Sovacool further predicts that SG research could deliver future innovations in technology, and economically reward entrepreneurs, investors, and supporting nations. SG is hailed by its advocates as a “magic bullet” or “emergency brake” on climate change. This means that SG could provide a rapid backstop against sudden and severe climate impacts.  

Nevertheless, as the study notes, SG does not address the underlying cause of climate change: increased concentrations of greenhouse gases in the atmosphere, for which human activities are primarily responsible. Therefore, if SG is implemented as the primary response to anthropogenic climate change, emissions will continue to rise. A portion of these emissions will also be absorbed by the oceans, furthering ocean acidification. SG is a partial solution that treats symptoms rather than the underlying cause.  

The research of Drs. Augustine Pamplany, Bert Gordijn, and Patrick Brereton, published in the journal Science and Engineering Ethics, explores the ethical desirability of SG. This literature review covers the ethics of both SG and carbon dioxide removal, and identifies evolving debate, gray areas, and underdeveloped arguments for and against each. Among arguments for SG, the authors note that SG is defended as an insurance policy. According to the review, this argument is relatively less popular among SG advocates. Given the prevailing literature’s neglect of this insurance framing, it is reasonable to infer that SG should only be deployed in a do-or-die situation. 

Based on their research, Pamplany et al. find that SG could stall a climate emergency and help to achieve the Paris Agreement goal. The study acknowledges that SG would delay climate change impacts and buy more time for mitigation strategies to accelerate. However, the researchers also find that SG is fundamentally flawed, and little more than a “band-aid” solution that distracts from mitigation efforts. The study further highlights distributive and procedural justice to be ethical challenges for SG. 

Overall, the researchers’ evaluation proves that despite the potential benefits, SG has significant risks that could outweigh these benefits for the climate. The researchers report that SG has feasibility challenges. The technology necessary to do SG research is not ready. Existing knowledge of SG is based on experiments and computer model simulations that are far from field tests and still inadequately understood. SG is based on trial and error and its effects remain largely theoretical, making it a risky option as a global policy.  

SG also poses the risk of imposing negative costs for the environment. For example, SG would affect the hydrological cycle, reduce global precipitation, and increase incidence of drought. This would heavily impact agriculture and fresh water supply. Additionally, SG with SAI would whiten the sky and cause afterglows near sunset. Whitening the sky during the day and afterglows near sunset—as seen after large volcanic eruptions—generates psychological consequences and public concerns.  Such acts are viewed by SG opponents as “playing God” and furthering domination of nature, contributing to SG’s unpopularity.   

The studies notes that SG also faces governance challenges. There are no established international global climate norms to govern development and deployment of SG schemes. This lowers public confidence in SG and raises accountability concerns should SG interventions cause disastrous consequences. Again, the world’s poorest countries, which contribute low greenhouse gas emissions, are expected to bear the biggest brunt of climate change impacts. As they have limited capabilities to develop and deploy SG schemes, they are excluded from solar geoengineering research programs, which raises procedural justice concerns.  

The studies assert that SG faces challenges in creating deployment-ready technology. The underlying technology of SG is immature and still in its infancy stages. Should an SG scheme suddenly fail, the earth would experience a large and abrupt temperature increase and continue to rapidly warm for several decades. A solar-geoengineered climate characterized by low solar radiation, low temperature, and high carbon dioxide would store much more carbon in the oceans and land. Sudden warming in the case of a catastrophic failure of an SG scheme would trigger release of stored carbon in land and ocean reservoirs into the atmosphere, exacerbating further warming. The researchers affirm that SG is far from perfect and would introduce new risks.  

If there is one key takeaway from this research for world leaders, it is that SG could cool the earth but fail to stem carbon dioxide buildup in the atmosphere. The perils of SG would threaten to cancel out the positive cooling impact. Hence, SG should only be considered as a last resort backup deployment strategy if climate change effects happen to be more abrupt and severe than previously anticipated and should all other interventions fail. Development and deployment of SG to lower global temperature and limit climate change risks requires careful attention to the real risks, costs, and benefits of developing and deploying it.