Solar Geoengineering Could Help Combat Climate Change

By Kevin Ritchart

While some of us enjoy spending lazy summer days soaking up the sun, scientists are exploring ways to keep a fraction of those rays from ever reaching the Earth’s atmosphere.

Earlier this year, the National Academies of Sciences, Engineering, and Medicine published a report urging the U.S. government to explore solar geoengineering as a means of combating climate change.

The report recommends that the federal government spend up to $200 million over the next five years to develop a national research program that will explore the viability of this technology as a means of helping cool the planet.

What Is Solar Geoengineering?

The idea behind solar geoengineering is to reflect more of the sun’s energy back into space through various techniques, including the injection of aerosols into the atmosphere.

Scientists have done some computer modeling to predict what might happen to Earth’s climate should solar geoengineering be accomplished successfully, but without more research, any potential conclusions drawn from the modeling studies are purely hypothetical.

How Does It Work?

The National Academies of Sciences, Engineering, and Medicine report outlined three solar geoengineering strategies that scientists consider viable options: stratospheric aerosol injection, marine cloud brightening, and cirrus cloud thinning.

Stratospheric aerosol injection (SAI) increases the number of small, reflective particles in the stratosphere to increase the reflection of incoming sunlight back into space. Modeling, using volcanic eruption as an analog, indicates that SAI can induce global cooling. But there’s uncertainty about whether the aerosols used in solar geoengineering would have an adverse effect on atmospheric chemistry as well as climate.

Marine cloud brightening (MCB) adds particles to the lower atmosphere (nearer the Earth’s surface) to increase the reflectivity of low-lying clouds over specific regions of our oceans. The potential drawback to this approach is a limited understanding of how aerosols and clouds will interact. Researchers have thus far been unable to perform MCB modeling because the key processes in need of observation are so small in scale that they cannot be observed in global climate models.

Cirrus cloud thinning (CCT) is a process of modifying the properties of high-altitude ice clouds, which increases the atmosphere’s transparency to thermal radiation. Scientists have limited knowledge regarding the properties of cirrus clouds and what can be done to alter them. Data from existing CCT climate modeling has shown mixed results.

"Some experts fear that the protections afforded to poorer regions could be pushed aside once the research begins."

The Air Up There

A Harvard University research team is planning what they’ve dubbed the Stratospheric Controlled Perturbation Experiment (SCoPEx for short), which will serve as some of the first significant studies in the realm of geoengineering field work.

The aim of the project is to send a high-altitude balloon into the stratosphere, where it will release small amounts of mineral dust into the air. By observing how the small quantities of particles react when they leave the balloon, researchers believe they will gain a better understanding of how aerosols will behave high up in the atmosphere.

Though SCoPEx researchers have said repeatedly that the project is small in scale and the particles will be released in the safest possible way, their efforts have drawn some negative attention from environmental groups.

What Are the Risks?

The report acknowledges the risks involved in geoengineering, which has developed into one of the more contentious issues in the creation of climate change-related policy.

Chief among those risks is that a large-scale solar geoengineering effort could upset regional weather patterns, for example changing the behavior of a monsoon or hurricane.

Another concern is that the implementation of solar geoengineering would diminish public pressure to reduce greenhouse gas emissions. Experts caution that whether or not the research results in a plan to move forward, we still need to maintain focus on reducing our carbon footprint worldwide.

Failing to follow through would jeopardize the goals of the 2016 Paris Agreement. Under the Paris Agreement, each of the countries involved must determine, plan, and regularly report on actions taken to mitigate the effects of global warming.

Lastly, if we started this effort of reflecting sunlight for a period of time, would we be able to stop? There’s a concern that halting the process would create an unacceptable level of rapid warming that could pose a danger to both people and the environment.

Money Matters

Solar geoengineering has bipartisan support from the U.S. Congress, which allocated $4 million to the National Oceanic and Atmospheric Administration (NOAA) in 2019 to conduct research into the technology. The NOAA and National Aeronautics and Space Administration (NASA) both helped fund the 2021 report on solar geoengineering along with the U.S. Department of Energy.

Proponents of moving forward with the research outlined in the report feel that the use of public funds will add transparency and accountability by creating clear rules about how and when to perform tests and gather data.

Critics don’t believe the safeguards detailed in the report will be enough, however. Some experts fear that the protections afforded to poorer regions could be pushed aside once the research begins.

A Measured Approach

The report also details a significant effort of transdisciplinary research, research governance, and robust stakeholder engagement, which is a departure from typical climate research programs. The following areas will be closely monitored as the research gets under way:

Context and goals. The hope is that all countries will engage meaningfully with the outcomes of the solar geoengineering research, weighing in with regard to social and environmental impact, aiding in the development of modeling scenarios, and outlining strategies for decision making when the best path forward might be unclear.

Impacts and technical dimensions. This includes gaining an enhanced understanding of the steps involved in successfully injecting particles into the atmosphere, the possible impact on the global climate and ecology, and the technical challenges associated with moving the solar geoengineering effort forward effectively.

Social dimensions. Researchers want to be sensitive to the public perception of their work while encouraging cooperation rather than conflict.

As research progresses, decisions will be made regarding the scope of the overall effort while helping to ensure that the process moves forward in an effective and societally responsible manner.

Where Do We Go from Here?

With the concept of solar geoengineering very much in its infancy, the questions that remain are how much information is needed to make an informed decision about implementing it on a large scale? And do the potential benefits to the world at large outweigh the risks?

Kevin Ritchart is a Thermo Fisher Scientific staff writer.