GEOENGINEERINGSolar Geoengineering to Cool the Planet: Is It Worth the Risks?

By Renée Cho

Published 16 May 2024

There is no international, national or state framework that currently governs geoengineering. As a result, one worrisome future scenario is that climate impacts in a particularly vulnerable country will be so severe that it resorts to deploying stratospheric aerosol injection (SAI, also called solar radiation management or SRM) on its own before the world is ready for it. This could cause political instability or provoke retribution from other countries that suffer its effects.

When I first wrote about geoengineering in 2012, it was considered far-fetched at best, and crazy by most. But 12 years later, while there is still controversy and considerable resistance to deploying it, respectable scientists and institutions are pushing for more research into geoengineering—the deliberate and large-scale intervention in our climate system to moderate global warming. Most of the current attention is focused on solar geoengineering, a strategy that involves reflecting sunlight away from Earth to cool the Earth. How much do we know about it and its risks? And where should we take it from here?

Why the Growing Support for Solar Geoengineering Research?
For many years, all geoengineering research was discouraged by many scientists and experts for fear it would provide an excuse not to cut emissions. Some right-wing politicians such as Newt Gingrich promoted it as a way to reduce global warming without having to cut emissions. Geoengineering research is also controversial because there were and still are many uncertainties about its potential effects on the climate system and ecosystems.

Nevertheless, James Hansen, director of the Program on Climate Science, Awareness and Solutions at Columbia’s Climate School, who first warned Congress about climate change risks in 1988, and a group of over 60 scientists are calling for more research into solar geoengineering. In addition, the US National Academy of Sciences, the Environmental Defense Fund, the Natural Resources Defense Council and the Union of Concerned Scientists all support solar geoengineering research. A 2023 White House report also expressed strong support for the research. 

Experts say support for research is growing because humanity is not doing enough fast enough to reduce carbon emissions to forestall severe and worsening climate impacts. Due to air quality regulations, a decrease in the sulfur dioxide aerosol emissions from coal plants and shipping that helped shield Earth from solar radiation has resulted in the world warming faster than was previously projected, according to a new study by Hansen and colleagues. They project that warming will surpass 1.5°C by the end of this decade and 2°C by 2050, which could result in disastrous climate impacts.

The potentially catastrophic climate impacts and the possibility of passing climate tipping points, such as thawing of the Arctic permafrost or the dieback of the Amazon rainforest, could necessitate the use of what were once unthinkable strategies.