In December 2016, soon after advisors to President Trump threatened to shut off NASA’s climate-observing satellites, California Governor Jerry Brown made a famous promise: “If Trump turns off the satellites,” he said while addressing a geoscience meeting, “California will launch its own damn satellites.” That promise is now a reality, with California and partners set to launch, by 2023, two satellites to spot and monitor plumes of planet-warming carbon dioxide (CO2) and methane. If all goes right, dozens more could follow.