Scientists studying ice cores are measuring the concentration of carbon dioxide gas in which layer of Earth’s atmosphere?

Scientists studying ice cores are measuring the concentration of carbon dioxide gas in the D. troposphere. The troposphere is the lowest layer of Earth's atmosphere where weather occurs and where the concentration of carbon dioxide and other greenhouse gases is most relevant to climate studies. Ice cores from glaciers and ice sheets trap air bubbles that provide a historical record of atmospheric composition, including CO2 levels from the troposphere.