Solar Geoengineering Could Save 400,000 Lives a Year, Georgia Tech Study Says

When it comes to finding solutions to climate change, there’s no shortage of technologies vying for attention, from renewable energy to electric vehicles to nuclear energy. One such contender, solar geoengineering, is favored by proponents who say it could quickly cool the planet and give the world time to fully implement efforts to limit emissions and remove carbon from the atmosphere.  

But that promise comes with risks, which include potentially poorer air quality or depleted atmospheric ozone – both of which can cause serious health issues of their own. 

A new Georgia Tech School of Public Policy-led study published in the Proceedings of the National Academy of Sciences (PNAS) suggests that while those risks deserve further consideration, solar geoengineering could save as many as 400,000 lives a year through a reduction in temperature-related deaths attributable to climate change.  

“An important question is how the reduction in climate risks from solar geoengineering compares to the additional risks its use entails,” said lead author Anthony Harding of the School of Public Policy. “This study offers a first step in quantifying the risks and benefits of solar geoengineering and shows that, for the risks we considered, the potential to save lives outweighs the direct risks,"  

Harding co-authored the PNAS article with Gabriel Vecchi and Wenchang Yang of Princeton University and David Keith from the University of Chicago. 

The researchers studied a climate change mitigation strategy called stratospheric aerosol injection (SAI), a type of solar geoengineering that involves spraying tiny reflective particles into the upper atmosphere. Those particles would then redirect some sunlight back to space and help cool Earth. 

The authors used computer models and historical data on how temperature affects death rates to see how much solar geoengineering might affect death rates, assuming a 2.5-degree Celsius increase in average temperature from pre-industrial levels and similar approaches to climate change as seen in the world currently. 

They found that cooling global temperatures by 1 degree Celsius with solar geoengineering would save 400,000 lives each year, outweighing deaths caused by solar geoengineering’s direct health risks from air pollution and ozone depletion by a factor of 13. This means that the number of lives saved due to solar geoengineering-caused cooling would be 13 times the number of lives potentially lost from solar geoengineering’s known risks. 

Many of those deaths would be avoided in hotter, poorer regions, the study notes. Cooler, wealthier regions could actually face increased cold-related deaths. 

Solar geoengineering has generated millions of dollars in funding and a recommendation by the National Academies of Science that the federal government should provide millions more toward research and the development of a risk-risk analysis similar to what Harding’s team produced. But the tech has also drawn concern, including from the Union of Concerned Scientists. That group says there’s too much environmental, ethical, and geopolitical risk to proceed without much more research. 

The authors caution that their study is an important starting point in better understanding solar geoengineering's promise and peril but is far from a comprehensive evaluation of the technology’s risks and benefits. 

They say their models are based on idealized assumptions about aerosol distribution, population and income growth, and other factors. They also can’t capture all of the real-world complexities that solar geoengineering would entail. They note their study also does not address all of the potential risks of solar geoengineering, such as possible impacts on ecosystems, global politics, or the possibility governments will rely on the technology to delay politically difficult emissions cuts. 

Still, the researchers say, the study suggests that for many regions, solar geoengineering could well be more effective at saving lives than emissions reductions alone and is worth keeping in the mix as the world searches for the optimal ways to cool our warming planet. 

“There’s no perfect resolution to the climate crisis,” said Harding. “Solar geoengineering entails risks, but it could also alleviate real suffering, so we need to better understand how the risks compare to the benefits to inform any potential future decisions around the technology.” 

The paper, “Impact of Solar Geoengineering on Temperature-Attributable Mortality,” was published in the Proceedings of the National Academy of Sciences on Dec. 17. It is available at https://doi.org/10.1073/pnas.2401801121.