Mexico Bans California Climate Startup’s Experiments to Cool Atmosphere

Make Sunsets, a firm led by tech entrepreneur Luke Iseman, had raised $750,000 in venture capital and other funds with the idea of selling “cooling credits” to U.S. firms, according to Mr. Iseman. He said the money would be used to release sulfur dioxide into the stratosphere, with the idea that the 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.

The so-called solar-geoengineering project launched one balloon in 2022 and was planning more launches this month from a site in the Mexican state of Baja California Sur.

Critics of solar geoengineering say not enough is known about how the particles will interact with other chemicals in the atmosphere and whether there will be unintended environmental effects.

On Jan. 13, Mexico’s Ministry of Environment and Natural Resources, or Semarnat, issued a statement stating it would prohibit the project from going forward.

The agency said any large-scale projects—and those that are seemingly large-scale but under development—involving solar geoengineering within Mexico would be halted.

Mexico’s Semarnat said it opposes the launches because there are currently no international agreements that address or regulate solar geoengineering activities. In 2010, delegates to the United Nations Convention on Biodiversity agreed to a nonbinding moratorium on geoengineering, which permitted small-scale research. Mexico is a signatory to the convention, while the U.S. isn’t.

“I expected and hoped for dialogue,” Mr. Iseman said from a small town in the Mexican state of Baja California Sur. “I’m surprised by the speed and scope of the response.” Mr. Iseman didn’t ask for permission…