A positive feedback loop in the atmosphere wherein an increase in temperature increases the water holding capacity. This will lead to an increase in the amount of atmospheric water vapour which, being a greenhouse gas, will in turn lead to another temperature increase. This process is better understood in the lower troposphere where there is reasonable certainty as to the feedback process. The upper atmosphere, while not as well understood in this regard, has a preponderance of evidence pointing to this. The temperature change is not uniform with height and the resulting changes in the vertical temperature gradient can partially compensate for the water vapour feedback.