The mesopause is the point of minimum temperature at the boundary between the mesosphere and the thermosphere atmospheric regions.
Due to the lack of solar heating and very strong radiative cooling from carbon dioxide, the mesosphere is the coldest region on Earth with temperatures as low as -100 °C (-148 °F or 173 K).
Air rising will expand and cool resulting in a cold summer mesopause and conversely downwelling air results in compression and associated increase in temperature at the winter mesopause.
[3] In recent years the mesopause has also been the focus of studies on global climate change associated with increases in CO2.
Unlike the troposphere, where greenhouse gases result in the atmosphere heating up, increased CO2 in the mesosphere acts to cool the atmosphere due to increased radiative emission.