Establishing precise measurements
Trained in chemistry, Keeling joined Scripps in 1956. To detect small changes in background air, he emphasised calibration, precision and site selection rather than treating local pollution fluctuations as a global trend.
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Building a long record
Carbon-dioxide measurements at Mauna Loa began in March 1958. The accumulating record showed seasonal variation alongside a multiyear increase, providing evidence for carbon budgets involving fossil-fuel emissions, ocean uptake and land vegetation.
From the curve to the carbon cycle
His research also addressed carbon in seawater and carbon-cycle models. His son Ralph later developed precise atmospheric-oxygen measurements that complemented carbon-dioxide data and helped distinguish ocean and land carbon uptake. The projects are connected but measure different gases.