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The increase in greenhouse gases causes the stratosphere to contract!

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For the first time, a team of scientists has demonstrated the existence of a global contraction of the stratosphere linked to the increase in greenhouse gases (GHG) atmospheric. A reduction in thickness which would not be without consequences… The results appeared on May 5 in the scientific journal Environmental research letters.

If the greenhouse gases that we emit are responsible for a warming of the lower atmosphere (that is to say. of the troposphere, see figure below), conversely they cause cooling of the layers above. Said in a very simplified way, by keeping the energy close to the ground, the GHG additional amounts deprive the upper atmosphere of an increasing fraction of the heat radiated by the Earth.

In response to these temperature changes, the troposphere expands while the stratosphere contracts. Also, the boundary between the two – the tropopause – is shifting towards higher and higher altitudes. Although the swelling of the lower atmosphere is relatively well documented, its higher altitude counterpart has at best been observed over limited areas and periods of time. In a new study, researchers have now proven the presence of a global and long-term stratospheric contraction.

The first layer of the atmosphere is the troposphere (between 0 and 12 kilometers above sea level). Above, we find the stratosphere (between 12 and 50 kilometers). Higher still, the mesosphere (between 50 and 80 kilometers) and the thermosphere (between 80 and 600 kilometers). The figures given are indicative. Credits: Wikimedia Commons.

Global contraction of the stratosphere: a first observational evidence

Using several sets of satellite observations and a set of numerical simulations, the authors found that between 1980 and 2018, the thickness of the stratosphere decreased by an average of 400 meters. An evolution which is mainly explained by the cooling due to the increase in the atmospheric concentration of GHG. Ozone, on the other hand, plays only a minor role, as evidenced by the results obtained by the team of scientists. In addition, in a future scenario where emissions do not decrease significantly, an additional reduction in thickness of about 1.3 kilometers is expected by 2080.

This study is the first observational evidence for the contraction of the stratosphere and shows that the cause is actually our greenhouse gas emissions rather than ozone. »Summarizes Paul Williams, researcher at the University of Reading (England) who did not participate in the study. ” Some scientists have started calling the upper atmosphere the ignorosphere because it is so poorly studied. This new document will support the case for better observations of this remote but critically important part of the atmosphere. “.

Such changes in thickness and density in the upper layers of the atmosphere are not without implications for our activities at the surface. Indeed, they have the potential to disrupt the trajectories of the satellites on which we base many services, the transmission of radio waves or even the proper functioning of the system. GPS. A non-exhaustive list which justifies the need to work on a more detailed understanding and quantification of the phenomenon.

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