Short answers, pulled from the story.
A single water molecule resides in the troposphere for only 9 to 10 days on average. This rapid turnover means the mean global content could cover the planet with a layer of liquid water roughly 25 millimeters deep.
Warming is expected to increase water vapor content by around 7 percent for every degree Celsius of warming. The Intergovernmental Panel on Climate Change expresses medium confidence that total water vapor increases by about 1 to 2 percent per decade.
Satellite data from the Moderate Resolution Imaging Spectroradiometer on NASA's Aqua satellite shows monthly averages of water vapor content in centimeters. These maps reveal how seasonal temperature shifts move humid bands north and south of the equator.
Water vapor consistently comprises more than 60 percent of total emissions during subaerial volcanic eruptions. Volcanic eruptions release variable amounts of water vapor into the atmosphere but play a trivial role compared to ocean evaporation.
Spectroscopic analysis confirmed water vapor in HD 209458 b located in Pegasus. Other exoplanets showing evidence include HAT-P-11b and K2-18b.