The weather measurements made here are so sensitive that when the observatory was built in 1956 scientists asked the national park to ban stoves at the summit cabin, fearing those emissions 6 miles away would throw off their readings. The park didn't, but the observatory managed to adjust. It has continuously recorded carbon dioxide (CO₂) and other human-produced greenhouse gas levels ever since, defining much of our understanding of global climate change. Tours of the facility are by appointment only.
Charles Keeling conducted much of the initial work at MLO, and was the first to consistently measure CO₂ at the same location. This allowed him to observe the steadily increasing levels – a trend referred to as the Keeling Curve – which is what first alerted scientists to the threat of global climate change.
Today, the observatory measures dozens of atmospheric gases, including methane, carbon monoxide, propane and nitrous oxide, and records particulate matter (pollution). The observations are taken when weather conditions ensure they capture an oceanic breeze untainted by Hawaiʻi's cities or volcanic eruptions.
