Answer:
This is true for some layers of the Earth's atmosphere.
Explanation:
As a counterexample: in the lowest layer of the atmosphere, with the highest density of gases, aka the Troposphere, the temperature decreases with increasing altitude. This relates to the sun heating up the surface some of which radiates back into the Troposphere.
However, the temperature increases with altitude in the Stratosphere (effect of ozone absorbing Sun rays), and it also increases with altitude in the Thermosphere (due to UV rays absorption).
The Mesosphere is another counterexample where the temperature decreases with increasing altitude.
