Many different types of solar radiation modification have been proposed, but most experts consider stratospheric aerosol injection to be both the most effective and least expensive approach.

The basic idea would be to produce tiny, reflective particles in part of the stratosphere between about 12 and 16 miles (20 and 25 kilometers) in altitude – which is above where airplanes typically fly. While some science fiction stories suggest that rockets might be used to do this, most experts think that modified aircraft would be required to distribute aerosols both high enough and consistently enough.

In 2021, the U.S. National Academies of Sciences, Engineering, and Medicine released a report on the topic of solar radiation modification, including stratospheric aerosol injection. The report was written by a committee of climate scientists, economists, lawyers and others. The group came to the conclusion that the U.S. should fund research on the topic. It recommended this in part because the consequences of solar radiation modification were still poorly understood.

This lack of understanding is quite a risk, since it remains unknown what might happen if the world pursues strategies like stratospheric aerosol injection, let alone if a specific country or organization decides to pursue these interventions by itself.

In our view, research into the potential consequences of stratospheric aerosol injection should include studies to examine potential changes in crop yields, shifts in global rainfall patterns or changes in critical regions of the Earth’s biosphere, like the Amazon rainforest. The fact is that we don’t know very well what would happen with stratospheric aerosol injection – which is why research on this topic is so critical.

We want to be absolutely clear that we are not advocating for the actual use of stratospheric aerosol injection.

The most direct way to avoid the uncertainty of solar radiation modification strategies like stratospheric aerosol injection is to address the root cause of global warming. That, as documented by many scientific studies, will require the aggressive reduction of emissions of carbon dioxide, methane and other greenhouse gases into the atmosphere.

This article is republished from The Conversation, an independent nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Patrick W. Keys, Colorado State University; Curtis Bell, US Naval War College; Elizabeth A. Barnes, Colorado State University; James W. Hurrell, Colo. The Conversation has a variety of fascinating free newsletters.

Read more:
How not to solve the climate change problem

Betting on speculative geoengineering may risk an escalating ‘climate debt crisis’

Patrick W. Keys receives funding from DARPA to conduct research on solar geoengineering.

Curtis Bell is engaged with a solar geoengineering project receiving funding from DARPA. He is affiliated with the United States Naval War College and Stable Seas, a non-profit maritime security NGO. His scholarly research does not represent the positions of the U.S. Navy, Department of Defense, or United States Government.

Elizabeth A. Barnes receives funding from DARPA to conduct research on solar geoengineering

James W. Hurrell receives funding from NOAA, DARPA, and private (gift) money to conduct research on solar geoengineering

Noah Diffenbaugh does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.