A startup has been launching sulfur dioxide into the sky, calling it climate tech.
The company Make Sunsets aims to cool Earth by mimicking volcanic eruptions—releasing sulfur dioxide high in the atmosphere to reflect sunlight back to space.
But the EPA is stepping in. In April, it demanded detailed answers: Where are the balloons launched? Where does the sulfur dioxide come from? Has the company consulted any regulators? Make Sunsets claims over 120 releases so far.
Sulfur dioxide is a regulated pollutant under the Clean Air Act, linked to lung irritation, acid rain, and haze. The EPA has controlled it since 1971.
Mexico has already banned the company. Now, the U.S. is issuing one of its first formal challenges to private geoengineering.
Make Sunsets must respond. The outcome could set the tone for how America regulates deliberate attempts to engineer the climate.
["EPA Demands Answers from Unregulated Geoengineering Start-Up Launching Sulfur Dioxide into the Air." EPA, 15 April 2025]