My research uses records from ancient glacial ice to answer questions about the Earth’s climate system and past atmosphere. One main direction of our current research is reconstructing past carbon monoxide (CO) concentrations and isotopic composition. CO is a highly reactive gas and is a major sink of atmospheric hydroxyl radicals (OH), which serve as the “cleansing agent” of the atmosphere. Another main direction of our research is using carbon-14 of ancient atmospheric methane to understand past changes in the global methane budget. Recent work using ancient ice from Greenland and Antarctica showed that a large and rapid increase in atmospheric methane concentration which happened about 11,600 years ago in association with a large and rapid warming event was likely due to increased methane emissions from wetlands in response to the warming.