Tim began working in the Carbon Dioxide Group at Scripps in 1983, measuring dissolved inorganic carbon (DIC) and Alkalinity in seawater. He earned his Ph.D. under C.D. Keeling in 1998, and then began a postdoc with Ralph Keeling establishing a measurement site for atmospheric O2/N2 and CO2 in Trinidad CA. His specialties include measurements of O2/N2 and CO2 ratio, CO2, and other greenhouse gases in air, and the inorganic carbon chemistry of seawater. He also installs and maintains instruments in Hawaii, helping to document the rising levels of CO2 in a time series popularly referred to as the "Keeling Curve".