March 2025 - 67th Anniversary Of The Start Date For Charles Keeling's Direct CO2 Measurement Series
One of the most important data collection projects on the planet is located on top of the world’s largest active volcano, Mauna Loa on Hawaii’s Big Island. Measurements of atmospheric carbon dioxide concentrations were started there by Charles Keeling and have been interrupted only twice, once due to funding issues, and once due to natural causes: In November 2022, lava blocked off access and power to the Mauna Loa Observatory.
But the active volcano was the least of Keeling’s problems. Over its 67-year history, the Keeling curve has been vulnerable to changes in policy at funding agencies and shifting political winds. Keeling, who died in 2005, spent his entire career measuring atmospheric CO2, and plenty of time and energy fighting to keep the project afloat. Keeling’s impact has been profound. “These measurements have revolutionized our thinking about how the Earth functions,” says Rob Jackson, an earth systems scientist at Stanford University.
The Keeling curve revealed that the biosphere breathes. In the Northern Hemisphere, atmospheric CO2 rises in winter, when photosynthesis is slowed, peaking at the start of the spring. When leaves emerge, photosynthesis accelerates, drawing down CO2. The Keeling curve shows this annual inhalation and exhalation of CO2, a seasonal change in the planet’s atmosphere that was previously invisible. Keeling’s data also help show that this effect is less pronounced in the Southern Hemisphere — and that the planet’s rotation contributes to relatively quick atmospheric mixing from east to west, and slower mixing along the north-south axis.
Keeling curve data also helped establish that fossil fuel emissions are increasing atmospheric CO2, and that the planet’s land and oceans are not able to take up enough of the gas to counteract human emissions.
EDIT
https://www.aps.org/apsnews/2025/02/keeling-measurements-co2-mauna-loa