Water Vapour

The most abundant greenhouse gas, water vapour is the water present in the atmosphere in gaseous form. Water vapour is an important part of the natural greenhouse effect. Although humans are not significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapour feedback. Water vapour also plays an important role in regulating the temperature of the planet, as clouds form when excess water vapour in the atmosphere condenses to form ice and water droplets, and precipitation (such as rain and snow).