The atmospheric sciences naturally include the study of the composition of earth's atmosphere and the transformation of chemical compounds in the atmosphere. The gaseous, liquid, and solid phases determine the radiative and dynamical properties of the atmosphere and sustain life on this planet. In turn, life influences the chemical composition of the atmosphere in both beneficial and deleterious ways. Researchers at the University of Colorado Boulder are engaged in projects ranging from laboratory and theoretical studies of the composition and chemistry of cloud and aerosol particles to field measurements of trace compounds in the atmosphere using ground-, aircraft-, and satellite-based sensors. Recent research topics include:, natural and anthropogenic causes for variations of ozone in the earth's stratosphere, the influence of volcanoes on atmospheric chemistry and radiative balance, the coupling of stratospheric ozone and dynamics, , remote sensing of clouds, microphysics of polar, midlatitude and tropical clouds, measurements of pollutants in the urban troposphere and assessment of their effects on human health, the response of mesospheric temperatures to changes in carbon dioxide, laboratory studies of uptake and reactivity of trace species on atmospheric aerosol particles, and studies of photo-reactive molecules and their clusters.