The climate crisis continues to be one of the most pressing global challenges, with no shortage of technologies aiming to mitigate its impacts. Efforts to reduce carbon emissions through renewable energy, electric vehicles, and nuclear energy have garnered widespread attention and support. However, one emerging technology that could offer a more immediate solution is solar geoengineering. Advocates argue that solar geoengineering, particularly through techniques like stratospheric aerosol injection (SAI), could quickly cool the Earth, providing much-needed time for the world to reduce emissions and remove carbon from the atmosphere.
However, like any potential climate intervention, solar geoengineering comes with both potential benefits and risks. Critics raise concerns about its unintended consequences, such as the potential for poorer air quality, ozone depletion, and disruptions to weather patterns—all of which could result in significant health problems and environmental damage. In recent years, research has sought to better understand the balance between these risks and the potential benefits of solar geoengineering. One such study, led by the Georgia Tech School of Public Policy and published in the Proceedings of the National Academy of Sciences (PNAS), takes a first step toward quantifying the risks and rewards of this controversial technology.
The study, authored by Anthony Harding from Georgia Tech, alongside Gabriel Vecchi and Wenchang Yang from Princeton University, and David Keith from the University of Chicago, analyzes the effects of solar geoengineering on human health. The researchers focus specifically on stratospheric aerosol injection, a method of solar geoengineering that involves releasing reflective particles into the upper atmosphere. These particles reflect a portion of sunlight back into space, which in theory would lower global temperatures, mitigating the effects of climate change.
The authors employed computer models and historical data to examine the potential impact of solar geoengineering on temperature-related mortality, assuming a 2.5-degree Celsius rise in average global temperature from pre-industrial levels—a scenario that reflects current climate change projections based on existing trends. According to their findings, cooling global temperatures by just 1 degree Celsius using solar geoengineering could prevent an estimated 400,000 climate-related deaths per year, which significantly outweighs the projected number of deaths caused by the direct risks associated with solar geoengineering, such as air pollution and ozone depletion.
The researchers estimate that the lives saved from the cooling effects of solar geoengineering would be 13 times greater than the number of lives lost due to its health risks. The study highlights that many of the lives saved would be in poorer, hotter regions of the world, where the effects of rising temperatures are felt most acutely. In contrast, wealthier, cooler regions could experience an increase in cold-related deaths, as temperatures would be lowered more than necessary in those areas. These findings suggest that solar geoengineering could be particularly beneficial in reducing temperature-related mortality in developing countries that are already struggling with the health impacts of extreme heat.
While the findings are promising, they come with several important caveats. The study’s authors stress that their analysis is a starting point for understanding the potential benefits and risks of solar geoengineering, but it is not a comprehensive assessment of the technology’s broader implications. The study assumes idealized conditions about aerosol distribution, population growth, and other variables, which may not reflect the complexities of real-world implementation. Moreover, the study does not address potential environmental and geopolitical risks, such as the potential disruption of ecosystems or the unintended consequences of large-scale international implementation of solar geoengineering.
Another key consideration is the potential for governments to rely on solar geoengineering as a substitute for reducing emissions. If the technology were to be deployed at scale, there could be concerns that it might delay or reduce political pressure for necessary emission cuts. Critics argue that this could create a moral hazard, allowing policymakers to defer meaningful action on climate change by relying on technological fixes rather than addressing the root causes of the crisis.
Despite these uncertainties, the researchers argue that solar geoengineering should not be dismissed outright. Instead, it should remain part of the conversation as the global community continues to explore ways to address the climate crisis. Harding, the lead author of the study, acknowledges that there is no perfect solution to climate change and that solar geoengineering comes with inherent risks. However, he stresses that the technology could alleviate significant suffering in the face of a warming planet. As such, it is essential to further study and understand the potential trade-offs of solar geoengineering in order to make informed decisions about its use.
One of the challenges in evaluating solar geoengineering is the complex interplay between its potential benefits and risks. While cooling the planet could save lives by reducing temperature-related mortality, there are also potential unintended consequences that could exacerbate other global issues. For example, stratospheric aerosol injection could lead to changes in regional precipitation patterns, potentially causing droughts in certain areas or disrupting agricultural production. Additionally, the technology could have long-term effects on global weather systems, which could be difficult to predict.
Furthermore, there are ethical and governance challenges associated with solar geoengineering. Who should have the authority to decide when and how to deploy such a powerful technology? Would solar geoengineering be used to address global inequality by helping the most vulnerable populations, or could it be leveraged for political or economic gain? These questions underscore the need for global cooperation and governance frameworks to ensure that solar geoengineering, if pursued, is done so in a way that is equitable and transparent.
Despite these challenges, solar geoengineering remains an intriguing option for climate mitigation. The potential to cool the planet quickly and reduce the health impacts of climate change is appealing, especially given the urgent need for action. However, as the research highlights, it is critical that solar geoengineering is considered as part of a broader, more comprehensive approach to climate change, one that prioritizes emissions reductions, carbon removal, and the protection of vulnerable ecosystems and communities.
Reference: Anthony Harding et al, Impact of solar geoengineering on temperature-attributable mortality, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2401801121