At any instant, Earth's atmosphere contains 37.5 million-billion gallons of water vapor– enough to cover the entire surface of the planet with one inch of rain,
if condensed.
This amount is recycled, through evaporation powered by the Sun, 40 times each year (aka The Hydrologic Cycle).
Earth's atmosphere is about:
78 percent nitrogen,
21 percent oxygen,
0.9 percent argon, and
0.1 percent other gases.
Trace amounts of carbon dioxide, methane, water vapor, and neon are some of the other gases that make up the remaining 0.1 percent.
The percentage of water vapor in air
ranges from 0.2% to 4%.
The average is claimed to be 2% to 3%.
Measurements of water vapor trends are difficult, and conflicting.
A small increase of water vapor could overwhelm any effect from CO2.
Especially because water and CO2 have overlapping absorption effects on some infrared energy wavelengths.
Much of real climate science is questions needing answers
Climate junk science is speculation and assumptions, falsely claimed to be "the science".