Planetary-scale solar geoengineering, specifically stratospheric aerosol injection (SAI), involves deliberately adding natural or artificial particles into the stratosphere to offset global heating from greenhouse gases. Proponents argue it could act as a planetary thermostat, reducing climate crisis harms by controlling global temperature. However, this approach is fraught with significant risks and limitations.
The Illusion of Global Temperature Control
Global temperature has become a primary index for climate policy since the early 2000s, with targets like the Paris agreement aiming to limit warming to 1.5C-2C. SAI seeks to lower this index by a few hundredths or tenths of a degree Celsius, but it does not address the root cause: greenhouse gas accumulation. Instead, it introduces new radiatively active particles, which may slow heat buildup in the climate system but offer no guarantees for reducing actual harms.
Key Problems with Solar Geoengineering
First, global temperature is a crude proxy for the diverse, multiscale harms of climate change. These include disruptions to regional weather systems, impacts of extreme events on vulnerable communities and ecosystems, and ocean acidification. Forcing down global temperature through SAI does little to defuse these critical risks and may even exacerbate them.
Second, artificially adding particles inevitably alters global atmospheric circulation dynamics, affecting regional and local weather. Evidence from volcanic eruptions and climate model simulations shows that SAI could influence hurricane tracks, the Indian monsoon, and El Niño patterns. This means solar engineers would bear responsibility for changes in everyone's weather, introducing unpredictable consequences.
A Call for Focused Climate Interventions
The focus of climate policy should be on direct interventions that tackle the causes of climate harms. This includes reducing greenhouse gas emissions, implementing carbon removal technologies, building resilience in human and ecological systems, and investing in human development drivers proven to reduce damage from dangerous weather. Pursuing SAI as a cost-effective solution distracts from these essential efforts, risking further environmental and social impacts.
Adopting global temperature as a controlled index through SAI creates an illusion of progress. True climate action requires reducing human emissions, not adding artificial materials to the atmosphere. As debates on geoengineering intensify, it is crucial to prioritize sustainable, evidence-based strategies over risky techno-fixes.
