Grantham should be putting his money into projects such as ARGO, studying ocean temperature and heat
interchange between the oceans and the atmosphere, and the CLOUD experiment at CERN, studying cloud formation and cosmic ray action.
Unfortunately, CO2 also moves from the
oceans and biosphere (
and sequestered fossil fuels, due to our actions) into the
atmosphere, which means you are talking about measuring a single
interchange rate
between various climate compartments, not total concentration changes in any one compartment.