Current atmospheric measurements
Ice core measurements – historical sampling
Ice core samples are obtained by drilling a long cylinder of ice (approximately 5 inches in diameter). The core is separated into 5 meter long segments and stored for further analyses. Electrical measurements are performed and stratigraphy is analyzed. Ice from the core is melted to measure the percentage of CO2 and various chemical techniques such as mass spectrometry and gas chromatography are used to analyze isotopic composition. The most widely used ice core data is the Vostok ice core from Antarctica.
Sources of error in reconstructing climate history using ice core data include determining age of the ice and correcting for gas exchange in snow prior to trapping of gas within bubbles enclosed in the compressed ice.