The idea of using solar geoengineering to combat climate change has been met with both interest and criticism. One California tech entrepreneur, Luke Iseman, had planned to launch sunlight-reflecting particles into the atmosphere, selling “cooling credits” to U.S. firms as a means of offsetting carbon emissions. However, Mexican officials blocked his project, leading Iseman to consider moving it to the U.S. or another country.
Iseman had raised $750,000 in venture capital and other funds for his startup, Make Sunsets, which aimed to release sulfur dioxide into the stratosphere. The idea was that these particles if spread across a wide area, would reflect sunlight away from the Earth and cool the atmosphere. The company promised that a “cooling credit” would offset the equivalent of a ton of carbon dioxide for a year.
Critics of solar geoengineering argue that not enough is known about how the particles will interact with other chemicals in the atmosphere and whether there will be unintended environmental effects. In January 2023, Mexico’s Ministry of Environment and Natural Resources issued a statement prohibiting the project from going forward, stating that any large-scale projects involving solar geoengineering within Mexico would be halted.
In April, Iseman launched a single weather balloon carrying several grams of sulfur dioxide and planned to launch several more balloons this month with larger amounts. While researchers who examined Make Sunsets’ plan said the small amount of sulfur dioxide carried by the weather balloons probably wouldn’t have resulted in much atmospheric cooling, the concept of solar geoengineering might have some merit once more research is conducted.
The idea of solar geoengineering has never been tested in the field, and it risks causing other effects in the atmosphere, according to climate scientists. A 2019 study by Harvard University scientists estimated that climate warming could be cut in half using reflective airborne particles. However, there might be an unexpected reduction in rainfall in a small number of areas around the world, according to a study, published in the journal Nature Climate Change.
In March 2021, a committee of the National Academies of Sciences, Engineering, and Medicine recommended that the U.S. invest as much as $200 million in a new solar-geoengineering research program, subject to public input and with careful governance over outdoor experiments. In April 2021, a field experiment involving a balloon release over Sweden—designed by Harvard University researchers and funded by private philanthropists—was halted amid opposition by environmental and indigenous groups.
While the potential benefits of solar geoengineering are clear, the risks and unknowns make it a controversial topic. As more research is conducted, it will be important to weigh the potential benefits against the risks and to approach the topic with careful governance and consideration of public input.
