https://blogs.scientificamerican.com/observations/encounters-with-the-keeling-curve/

From 1969 to 1972 I was a geologist on the staff of the Hawaiian Volcano Observatory. Though our focus was an eruption of nearby Kilauea, we visited the summit of Mauna Loa once each year to make geodetic measurements as a way to monitor whether or not the volcano was inflating toward a possible eruption. During each ascent, we stayed overnight at the “Keeling laboratory” to help acclimate our bodies to the even thinner air at the summit elevation of nearly 14, 000 feet.

Thumb-tacked to the wall of our “motel” was an up-to-date hand-drafted graph of Keeling’s carbon dioxide measurements. My HVO colleagues and I had no idea that we were seeing the infancy of a graph that would eventually document incontrovertible evidence of humankind’s impact on global climate change! Charles David Keeling deserves to be smothered in credit for his experiment, though not in a CO2-rich environment!