In addition to the carbon dioxide and oxygen discussed
earlier, several other gases in Earth’s atmosphere affect daily
life. Over the current range of terrestrial temperatures,
the atmospheric abundance of water varies from time to
time and from place to place. In warm, moist climates, water
vapor may account for as much as 3 percent of the total
atmospheric composition. In cold, arid climates, it may be
less than 0.1 percent. The continual process of condensation
and evaporation of water involves the exchange of
thermal and other forms of energy, making water vapor a
major contributor to Earth’s weather.