The U.S. Environmental Protection Agency under the Trump administration has launched an investigation into a small geoengineering startup for allegedly polluting the air by releasing sulfur dioxide. The startup, Make Sunsets, consists of just two Silicon Valley founders who have raised $750,000 from investors including Boost VC, Draper Associates, and Pioneer Fund. Their method involves filling weather balloons with sulfur dioxide and hydrogen gas, and releasing them into the upper atmosphere. When these balloons burst at altitudes above 66,000 feet, they disperse sulfur dioxide particles designed to reflect sunlight and bring about a slight cooling effect on Earth’s climate. The company monetizes this approach by selling “cooling credits,” which reflect the estimated reduction in atmospheric warming each balloon achieves.
Make Sunsets asserts the legality of its practice, citing compliance with the Weather Modification Act of 1976 and reporting annually to the National Oceanic and Atmospheric Administration (NOAA). However, the EPA contends that sulfur dioxide qualifies as a regulated air pollutant, and the agency intends to probe deeper into the environmental impact of the startup’s activities. EPA Administrator Lee Zeldin described the inquiry publicly, indicating the agency’s commitment to examining this unorthodox approach to climate mitigation.
The concept of deliberately manipulating Earth’s climate, commonly referred to as geoengineering, remains deeply contentious. Advocates argue such measures are urgently needed as humanity struggles to reduce reliance on fossil fuels and curb emissions. Detractors caution against the risks, pointing out the potential for unintended effects on weather patterns, including disrupted rainfall distributions. Scientists and policymakers warn that releasing airborne pollutants may yield unknown regional impacts, stressing the uncertainty inherent in intervening directly in Earth’s atmospheric systems. Moreover, sulfur dioxide drifting toward ground levels could potentially increase respiratory ailments such as asthma.
Despite these concerns, the scientific foundation underpinning sulfur dioxide’s reflective capability is not untested. Historical events, such as the reduced sulfur content in marine fuels in 2020, provided unintended demonstrations of how the substance affects global albedo—the degree to which sunlight is reflected back into space. Notable scientists in climate research have occasionally endorsed geoengineering concepts; however, substantial caution persists, acknowledging the complex and unpredictable interplay of climate systems.
Nevertheless, the EPA’s targeting of Make Sunsets invites scrutiny given the administration’s broader regulatory stance. The Trump-led EPA has actively promoted coal industry policies known to significantly increase pollutants like sulfur dioxide. Power plants alone emitted around 650,000 tons of sulfur dioxide in 2023, dwarfing emissions attributable to the incremental balloon releases initiated by the tiny startup—a striking contrast noted by observers, highlighting the seeming disparity between the EPA’s regulatory actions across different sources of pollution.
