The amount of water that can be dissolved in air changes as a function of the temperature. In general, this means that increasing the temperature of air by 1ËšC increases how much water can be dissolved in it by 7%. The precise values for any temperature change can be calculated using the Clausius-Clapeyron equation.
This is relevant to climate change for two reasons. Firstly, water vapour is a powerful greenhouse gas. Higher temperatures cause more evaporation and allow air to be more water-saturated, thus permitting further warming. Secondly, increased temperatures affect precipitation patterns through changes in the water capacity of air. The general trend is towards more extreme precipitation, more drought, greater annually averaged precipitation in middle and high latitude locations, and decreased precipitation in the tropics.