Dr. Butler oversaw the nation’s continuing measurements of atmospheric constituents that affect the world’s climate, including greenhouse and ozone-depleting gases, aerosols, and surface radiation. Dr. Butler’s published works address the distribution and cycling of gases in the atmosphere, their production and consumption by the ocean, their exchange across the air-sea interface, their distribution in polar snow, and methods for their analysis. He was a regular contributor to international documents on stratospheric ozone depletion, atmospheric chemistry, and global warming.