Carbon dioxide binds heat but also radiates it efficiently. In a thin upper atmosphere, heat escapes into space at an ever-accelerating rate.
Human greenhouse gas emissions caused by warming the earth’s surface, but in the upper layers of the atmosphere the effect is different.
Satellite measurements by the U.S. Space Agency’s NASA show that climate change has led to the cooling and shrinking of the upper atmosphere.
Scientists have long predicted the effects of carbon dioxide and other greenhouse gases on the Earth’s upper atmosphere. However, decades of measurements are required to detect change.
Nasa based its observations on measurements from three satellites over a period of nearly 30 years.
The satellites measured temperature and pressure at an altitude of 50 to 100 kilometers in the mesosphere, the coldest layer of the Earth’s atmosphere.
At its upper limit, the temperature drops to one hundred degrees below freezing.
About the results it turned out that the mesosphere has cooled about 2-3 degrees above the poles and shrunk by about 150–200 meters in a decade. Cooling was observed at almost all measured heights.
According to the researchers, the development will continue in the future if the amount of carbon dioxide in the atmosphere continues to increase.
Research was published Journal of Atmospheric and Solar-Terrestrial Physics.
Greenhouse gases act in the lower and upper atmospheres in opposite ways, as the air is very dense on the ground.
The higher you travel from the Earth’s surface, the thinner the air becomes. At the upper limit of the mesosphere at an altitude of one hundred kilometers, the atmospheric pressure is only 0.001 per cent of the surface atmospheric pressure.
“Carbon dioxide binds the earth’s heat like a blanket of body heat,” says Researcher at Hampton University James Russell in the bulletin.
“There are a lot of molecules in the lower atmosphere close to each other, so they capture the heat of the Earth and transfer it from one molecule to another. So they retain heat like a blanket. ”
Carbon dioxide binds heat but also radiates it effectively.
In the upper atmosphere, there are fewer molecules and they are located farther apart. Thus, the heat bound by carbon dioxide does not transfer from one molecule to another but escapes into space.
As the amount of carbon dioxide and other greenhouse gases in the upper atmosphere increases, heat radiation into space accelerates and the temperature of the atmosphere decreases. The cooling air, in turn, shrinks like a balloon in cold weather.
Mesosphere cooling can also be seen in the clouds hovering above the Earth’s poles.
So called illuminating night clouds are formed during the summer at an altitude of 50 to 80 km. They glow in the sky blue and silver as soon as the sun sets or just before it rises.
Clouds require water vapor, dust particles, and very low temperatures to form. In recent years, night clouds have become brighter, spread over a wider area, and appeared in the sky more and more often.
According to the researchers, the use of clouds can only be explained by the cooling of the upper atmosphere and the increase in water vapor. Both of these phenomena are in turn linked to climate change.
Upper atmosphere cooling does not directly affect ground events, but may have an effect on the operation of low-orbiting satellites, for example.
In near space, atmospheric friction pushes satellites out of orbit. When a satellite drifts low enough, accelerating speed and friction cause it to scorch and fall to the ground.
As the mesosphere shrinks, atmospheric friction decreases, which can reduce interference to satellites. However, friction has its own role in cleaning up space debris, as it also pushes broken equipment down orbit.
The contraction of the atmosphere may therefore lead to more and more debris accumulating on the Earth’s orbit.