This award supports a two-year project to continue work developing the techniques to make carbon monoxide (CO) measurements in ice core samples. Carbon monoxide is an important atmospheric chemical constituent as it is a primary sink for hydroxyl radical (OH) (and therefore influences the oxidizing capacity of the atmosphere) and because the concentrations of three major greenhouses gases , carbon dioxide (CO2), methane (CH4) and ozone (O3) are directly tied to the concentration of CO. In light of recent anthropogenic increases in the emissions of CO, CO2, CH4 and NOx, it is desirable to understand this complex chemical system and the changes in the greenhouse forcing resulting from perturbation. Because it is difficult to test the accuracy of models for past and future conditions for which no direct atmospheric measurements of trace gas concentrations are available these measurements must be obtained in other ways. Polar ice cores provide a means to make these measurements. Further work is necessary to refine the analytical technique and additional measurements are necessary to investigate the accuracy of these results and to establish the nature of temporal trends in CO. It is anticipated that the CO record, combined with existing or new data for CO2, CH4 , N2O and other paleoclimate variables, will provide further constraints on model studies of the effect of changing atmospheric chemistry on greenhouse forcing.