Ralph’s work centers on long-term measurements of the major constituents in air. He has been on the faculty at the Scripps Institution of Oceanography, UC San Diego, since 1993.
He was the first to demonstrate that the O2 content of air is decreasing due to the burning of fossil-fuels and has directed a program to track this decrease since 1989. Since 2005 he has also directed the Scripps CO2 program which sustains the iconic record of carbon dioxide at Mauna Loa and other sites, begun by his father, Charles D. Keeling. He is engaged in ongoing research to refine estimates of sources and sinks of carbon dioxide using atmospheric measurements. Keeling has received the Rosenstiel Award in marine and atmospheric chemistry, the Humboldt Research Award, and is a Union Fellow of the AGU.