Which positive feedback occurs when warming increases atmospheric water vapor?

Which positive feedback occurs when warming increases atmospheric water vapor? Water vapor feedback is the positive feedback in which warming increases atmospheric water vapor.

Warmer air can hold more water vapor because saturation vapor pressure rises with temperature, a relationship described by the Clausius–Clapeyron relation. As evaporation adds moisture to the atmosphere, that water vapor absorbs outgoing infrared radiation and adds further warming.

The process is a feedback, not the original forcing in this example. An initial warming—such as warming caused by increased carbon dioxide—allows the atmosphere to contain more moisture. The added water vapor then strengthens the greenhouse effect, which causes more warming and permits still more moisture.

Water vapor is not usually treated as a primary long-lived driver of modern climate change because its atmospheric amount responds quickly to temperature and precipitation. Clouds complicate the picture: water vapor can contribute to cloud formation, but cloud feedback is a separate mechanism with different and more uncertain effects. Water vapor feedback amplifies warming rather than creating energy from nothing.