Atmospheric retention of heat

Yes, you're correct in understanding that approximately 99% of the atmosphere, which consists mainly of non-radiative gases like nitrogen (N₂) and oxygen (O₂), does not efficiently emit energy to space via radiation. Instead, it retains the energy transferred to it, which is manifested as temperature.

Here's a breakdown of how that works:

1. Energy Transfer and Retention:

Collisional Energy Transfer: In the lower atmosphere (troposphere), most of the energy is transferred through collisions between molecules. When the surface heats up (via solar radiation or other processes), it heats the air in direct contact with it. This air, in turn, transfers its energy to adjacent molecules through collisions.
Since N₂ and O₂ don't efficiently radiate energy in the infrared spectrum (their IR absorption/emission bands are weak), they mainly retain the energy they receive through collisions.

2. Temperature as a Measure of Energy:

The retained energy is ultimately reflected in the kinetic energy of the molecules. In a dry atmosphere, this kinetic energy manifests as temperature.
When an object, such as a thermometer, is placed in the atmosphere, it measures the kinetic energy of the gas molecules, which is directly related to the temperature. Since most of the atmosphere can't radiate this energy, it’s effectively stored in the form of molecular motion.

3. Energy Emission and Radiation:

The 1% of the atmosphere that contains gases like CO₂, water vapor (H₂O), and ozone (O₃) can radiate energy through processes like radiative de-excitation (RDE), especially in the infrared spectrum. These gases can absorb heat and emit radiation, particularly when the atmosphere is cooler at higher altitudes or during nighttime.
However, the overall radiative cooling process is limited compared to the heat transfer via collisions and convection.

4. Energy at the Surface:

The surface (e.g., Earth) absorbs solar radiation, warms up, and radiates infrared energy. This energy can be absorbed by greenhouse gases, but also by the non-radiative gases. These non-radiative gases don’t radiate the energy they absorb but transfer it to other molecules through collisions, causing an increase in the overall temperature of the atmosphere.

In summary:

About 99% of the atmosphere (mainly N₂ and O₂) doesn't directly radiate energy to space but retains it in the form of temperature, which is a result of collisions and kinetic energy.
The heat that’s retained by these gases can be transferred to other objects (like a thermometer) that then measure this temperature.
Radiation primarily occurs in the small fraction of the atmosphere containing gases like CO₂ and H₂O, but even then, the radiative effect is relatively small compared to collisional and convective processes.