Is Solar Geoengineering a Solution to Climate Change?

In the face of climate change, a newer solution has recently been gaining traction: solar geoengineering. Rapidly rising temperatures call for a serious evaluation of technologies that could mitigate global warming, as simply cutting global greenhouse emissions might not be enough. 

Solar geoengineering refers to a set of emerging approaches that could cool the Earth by reflecting solar radiation back to space, in effect counteracting temperature rise. One technique called stratospheric aerosol injection (SAI) involves shooting tiny reflecting particles, known as aerosols, into the atmosphere. Another strategy called Marine Cloud Brightening (MCB) sends salty aerosols into marine cloud layers with the aim of creating whiter clouds to decrease solar radiation reaching the Earth’s surface. 

Stratospheric aerosol injection (SAI)

How might solar geoengineering combat climate change? 

Though solar geoengineering would not address the root cause of climate change—namely, the emissions of heat-trapping gases—climate models have consistently demonstrated that when used sparingly and in conjunction with emission cuts, this approach may contribute towards reducing climate impacts including extreme temperatures, changes in water availability, and intensity of tropical storms.  

According to the Royal Society of Mathematical, Physical, and Engineering Sciences, research indicates that solar geoengineering would produce a different climate response than would conventional carbon dioxide removal technologies (CDR) because the effects would manifest much more quickly (in a matter of months) and would be reversible. Comparatively, CDR effects are postponed by decades, suggesting that solar geoengineering might complement CDR. 

Risks of Solar Geoengineering 

Despite such advantages, solar geoengineering poses a number of risks that warrant careful consideration. Alongside the physical ramifications of causing residual regional temperature abnormalities, such as decelerating the recovery of stratospheric ozone, solar geoengineering may present social challenges. At the forefront of these dangers is the “moral hazard” of technology serving as a substitute for emissions reductions instead of pushing for the transition towards a low-carbon economy. 

Additionally, considering its global implications, the governance of solar geoengineering has been a popular subject of discourse. Many critics argue that the deployment of solar geoengineering is impossible to regulate equitably and effectively. They’ve expressed concerns over how factors such as the manner and intensity of execution would render democratic decision-making harder to preserve. This is especially pertinent since the type and degree of deployment would have different results in different countries, therefore unevenly distributing risks and leaving lesser developed countries the most vulnerable. 

It’s also crucial to understand the human health effects of the solar geoengineering aerosols. Inhalational and epidemiological studies by the International Agency for Research on Cancer suggest that “occupational exposure to strong inorganic mists containing sulfuric acid is carcinogenic for humans.” On a more global scale, there seems to be a correlation between climate change and vector-borne diseases, particularly malaria. Alongside an expected increase in population, evidence reveals a possible expansion of a particular malaria parasite into southern Africa and a reduction of transmission in central Africa. Thus, solar geoengineering may inadvertently facilitate malaria transmission in developing countries. 

Thus far, there is agreement in the scientific community that further research in solar engineering is imperative before any sort of deployment. In March of 2021, the U.S. National Academies of Sciences, Engineering, and Medicine recommended that the U.S. government introduce a federal research program to examine solar geoengineering, involving an investigation of the environmental science behind the technology, as well as the ethics of it. The proposal contains a code of conduct and public registry for research propositions and results, thereby encouraging international engagement. Whether or not solar engineering is the correct approach, one thing is clear: governments need to thoroughly evaluate all of their options and accelerate their climate response agenda.