David Sayres joined the group in 1999. His technical expertise is using absorption spectroscopy, with a focus on the ultra-sensitive Integrated Cavity Output Spectroscopy (ICOS) technique, to accurately measure trace gases in the atmosphere. Research interests include understanding the mechanisms that control the humidity of the upper troposphere and lower stratosphere using in situ measurements of water vapor isotopes and other tracers. More recently, his research has focused on quantifying methane emissions from the Arctic region using flux measurements from an aircraft of methane isotopes and other tracers.