To Solar Geoengineer or Not, That is the Question

Jennifer Leakos

The emerging field of solar geoengineering could help mitigate some of the risks of climate change, but has people divided in ways previously only accomplished by black licorice.

Background: Geoengineering, as defined by the Intergovernmental Panel on Climate Change, is technology that aims to deliberately alter the climate system in order to avoid the impacts of climate change. Since the world will likely pass the 2°C global warming threshold, anything that could help is tempting to use.

There are two main groups: Carbon geoengineering, that targets the removal of carbon from the atmosphere and includes direct air capture, and solar geoengineering, that aims to reflect or block solar radiation. Pretty much sunscreen for the planet.

Even within solar engineering, there are different types:

  • Surface albedo enhancement: Much less risqué than it sounds, it’s essentially just increasing how much sunlight reflects on Earth’s surfaces.
  • Marine cloud brightening: Like an IRL Instagram Clarendon filter, the brightness of the low clouds off the ocean are increased so that they reflect more sunlight.
  • Stratospheric aerosol injection: Spraying aerosols directly into the atmosphere to reflect the sun’s light. This has received its share of media attention, and not all of it positive.
  • Space-based method: As sci-fi as it gets, this involves placing a giant mirror in space to reflect the sun’s rays before they ever hit Earth.
  • Cirrus cloud thinning: A particular type of cloud called cirrus clouds are made of ice crystals and are found much higher in the atmosphere. They absorb solar radiation instead of reflecting it, so thinning them out with aerosols could decrease warming.

Types of solar engineering

Types of solar engineering
Courtesy of the US National Ocean and Atmospheric Administation

What we don’t know: There are still many unknowns about solar geoengineering, including its effects on ecosystems, the water cycle, and weather patterns. On top of those is the risk of termination shock – if we were to rely on solar geoengineering and then to suddenly stop using it, there could be a rapid rise in temperature with even more worse impacts.

This leads to a split of opinions on whether to pursue or even research solar geoengineering.

The supporters: On one side of the debate is a group of scientists who support this research, who believe that there are more risks from the world failing to stay within 2°C of heating. The unknown risks and costs of solar geoengineering have to be weighed against the unknown risks and costs of global warming, they argue.

Solar geoengineering interventions are expected to cost in the tens of billions – a lot, but a drop in the bucket compared to the tens of trillions needed for a full energy transition investments.

How solar geoengineering could flatten the curve

How solar geoengineering could flatten the curve
Courtesy of Knowable Magazine

Those against: The Union of Concerned Scientists signed a letter laying out their concerns around the moral hazard of solar geoengineering and that it could delay investments into permanent solutions.

Even the public has mixed perspectives on geoengineering. According to Pew Research Centre, three quarters of Americans are either very concerned or somewhat concerned about its use.

Previous experiments

In December 2022, a startup called Make Sunsets sent a balloon filled with sulfur dioxide into the skies of Mexico, in order to further prove out stratospheric aerosol injection. Unfortunately, their hopes were figuratively deflated when the Mexican government banned all future solar geoengineering experiments.

Harvard had planned to do a project in Sweden in June 2021, but was suspended until a full public engagement procedure could be completed.

Zoom out: Geoengineering is not a long-term fix, and the world still needs to reach net zero to hit warming targets. But past generations have made the mistake of avoiding short-term fixes leaving current generations with longer-term problems.

At the very least, solar geoengineering is an area that should be researched further… just in case we need it.

+Additional Listening: Solar Geoengineering – should we go there?