Permanent gases have concentrations that do not vary during our lifetimes (perhaps there is some variation over a timescale of millions of years). The trace gases are those whose concentrations are much much less than 1% (their concentrations are millionths of the atmosphere).

These gases do vary on a much shorter time scale. Water vapor varies with the weather and location; the higher the temperature, the higher the water vapor content tends to be (though this is not a sure thing).

Carbon dioxide varies seasonally, with the dormancy of deciduous green plants in the winter causing the carbon dioxide concentration to go up (there are fewer plants to absorb CO₂) and the active growth of the plants in the summer causing concentrations to decrease.

Ozone (and other pollutants) vary with time and location. The ozone in the stratosphere (which is not considered a pollutant since it enhances the viability of life on Earth) also varies seasonally and with latitude. Higher amounts of stratospheric ozone exist during very early and very late winter, and at higher latitudes.