The mesosphere is the least hot layer.
Earth's Atmospheric Layers and Temperatures
The Earth's atmosphere is divided into several layers, each with distinct temperature characteristics. While the thermosphere has extremely high temperatures at its upper reaches, the mesosphere, located between the stratosphere and thermosphere (roughly 50-87 kilometers above Earth's surface), experiences the lowest temperatures. Temperatures in the mesosphere can plummet to as low as -90°C (-130°F) near its upper boundary.
- Thermosphere: The highest layer, characterized by extremely high temperatures due to absorption of high-energy solar radiation. However, the air is so thin that this heat wouldn't feel warm to a human.
- Stratosphere: The layer above the troposphere, containing the ozone layer which absorbs UV radiation, causing temperatures to increase with altitude.
- Mesosphere: The layer below the thermosphere, where temperatures decrease with increasing altitude, resulting in the coldest temperatures in the Earth's atmosphere.
- Troposphere: The lowest layer, where most weather occurs. Temperatures generally decrease with altitude.
This information is consistent across multiple reliable sources, including Center for Science Education, National Oceanic and Atmospheric Administration (NOAA), and homework.study.com.
Note that discussions of "layers" in other contexts, such as 3D printing or clothing layers (Reddit thread on clothing layers), are not relevant to the question of atmospheric temperature. Those references discuss managing heat differently and are not comparable to the atmospheric layers.
