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The mesopause is the temperature minimum at the boundary between the mesosphere
Mesosphere

The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located from about 50 km to 80-90 km altitude above the Earth's surface....
 and the thermosphere
Thermosphere

The thermosphere is the layer of the earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization....
 atmospheric regions. Due to the lack of solar heating and very strong cooling by radiative emission from CO2, the mesopause is the coldest place on Earth with temperatures as low as -100°C (-146°F or 173 K
Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
) [1]. The altitude of the mesopause for many years was assumed to be at around 85km, but observations to higher altitudes and modeling studies in the last 10 years have shown that in fact the mesopause consists of two minima - one at about 85 km and a stronger minimum at about 100km [2].

An interesting feature is that the summer mesopause is cooler than the winter.






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The mesopause is the temperature minimum at the boundary between the mesosphere
Mesosphere

The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located from about 50 km to 80-90 km altitude above the Earth's surface....
 and the thermosphere
Thermosphere

The thermosphere is the layer of the earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization....
 atmospheric regions. Due to the lack of solar heating and very strong cooling by radiative emission from CO2, the mesopause is the coldest place on Earth with temperatures as low as -100°C (-146°F or 173 K
Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
) [1]. The altitude of the mesopause for many years was assumed to be at around 85km, but observations to higher altitudes and modeling studies in the last 10 years have shown that in fact the mesopause consists of two minima - one at about 85 km and a stronger minimum at about 100km [2].

An interesting feature is that the summer mesopause is cooler than the winter. This is sometimes referred to as the mesopause anomaly. It is due to a summer-to-winter circulation giving rise to upwelling at the summer pole and downwelling at the winter. 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. It should be noted that in the mesosphere
Mesosphere

The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located from about 50 km to 80-90 km altitude above the Earth's surface....
 the summer-to-winter circulation is due to gravity wave
Gravity wave

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the Interface between two media which has the restoring force of gravity or buoyancy....
 dissipation, which deposits momentum against the mean east-west flow resulting in a small north-south circulation [7].

In recent years the mesopause has also been the focus for studies on global climate change
Climate change

Climate change is any long-term significant change in the expected patterns of average weather of a specific region over an appropriately significant period of time....
 associated with increases in CO2. Unlike the troposphere
Troposphere

The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its water vapor and particulate....
, where greenhouse gases result in the atmosphere heating up, increased CO2 in the mesosphere
Mesosphere

The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located from about 50 km to 80-90 km altitude above the Earth's surface....
 acts to cool the atmosphere due to increased radiative emission by CO2. This results in a measurable effect - the mesopause should become cooler with increased CO2. Observations do show a decrease of temperature of the mesopause, though the magnitude of this decrease varies and is subject to further study [3]. It should be noted that modeling studies of this phenomenon have also been carried out [4][5][6].