A temperature inversion has a negative lapse rate. Negative numbers are always less than positive ones, and since adiabatic lapse rates are positive in value, a temperature inversion is absolutely stable. In diagram on this page, the inversion layer (where the temperature inversion exists, or the environmental lapse rate is negative) is the upper part of the red environmental temperature profile, where the line slopes upward to the right.

In fact, the inversion is an extreme case of absolute stability. Consider that the restoring force on a displaced air parcel in a stable atmosphere is proportional to the difference in temperature between the parcel and the surrounding air. As the parcel temperature drops according to the adiabatic lapse rate, the environmental temperature is increasing, so the difference between the temperatures is becoming larger and larger very fast. Thus, the restoring force is very strong, and convection is strongly suppressed.

Thes suppression of vertical motion is what traps clouds and pollution in a layer near the ground in Los Angeles, since L.A. has a temperature inversion aloft most days during the late spring through late fall.