Mauna Loa Observatory, famous for its long-running carbon-dioxide record, is in Hawaii.
The observatory sits on the northern flank of Mauna Loa, a volcano on Hawaiʻi Island in the U.S. state of Hawaii. Its high elevation and remote location help researchers sample air that is relatively well mixed and less directly affected by nearby cities, vegetation, or local pollution.
Continuous carbon-dioxide measurements began there in March 1958 under the direction of Charles David Keeling of the Scripps Institution of Oceanography. The resulting record became known as the Keeling Curve. Its regular seasonal rise and fall reflects plant growth and decay, while its long-term upward trend shows the buildup of atmospheric carbon dioxide from human activities.
A common mix-up is Mauna Loa versus Mauna Kea. Mauna Kea is also on Hawaiʻi Island and hosts major astronomical observatories, but the famous CO2 monitoring station is Mauna Loa Observatory. The station is part of NOAA’s atmospheric monitoring network and has supported research on gases, weather, solar conditions, and other atmospheric phenomena.