The stratosphere is around 400 meters thinner than it was in the 1980s. The main reason for this is the greenhouse gas emissions, reports an international team of researchers. If they continue to rise, the air layer could shrink another 1.3 kilometers by 2080.
The troposphere is the lowest “level” of the atmosphere, begins on the ground and extends to the stratosphere. The border area between the two layers is called the “tropopause”, which is about eight kilometers above sea level in the polar regions and about 16 kilometers above sea level on the equator.
The troposphere is getting warmer and warmer as a result of the increasing carbon dioxide (CO2) since the industrial revolution and the associated increased greenhouse effect and expands due to the global warming. When this was found out in the early 2000s, the hypothesis was put forward that the stratosphere, which is around 40 kilometers thick on average, should contract as a result.
For their study published in the journal “Environmental Research Letters”, the scientists led by Petr Pisoft from the University of Prague examined “reanalysis data” in which various global meteorological data sets and models flow together. They found “evidence of a significant contraction of the stratosphere in the past few decades,” as the researchers write in their work.
100 meters per decade
According to this, the expansion of the stratosphere shrank between 1980 and 2018 at a speed of more than 100 meters per decade. The researchers’ models predict a contraction of a further 1.3 kilometers by 2080, which corresponds to a decrease of 3.7 percent compared to the mean stratospheric thickness from 1980-2018.
The researchers assume that this shrinkage also took place before the 1980s and the overall decline is likely greater than the 400 meters observed so far. However, there is not enough data from this high altitude prior to 1980 to verify this.
Cooling off and thinning
The background to the contraction is the different effects of carbon dioxide in the various layers of the atmosphere: While the greenhouse gas in the troposphere makes a significant contribution to heating, it has the opposite effect in the stratosphere: there it leads to cooling. In addition to the increase in the CO2 concentration, the ozone layer is also thinning at the same time. As a result of both effects, stratospheric temperatures have fallen by around three degrees Celsius over the past three decades.
“Increasing CO2 concentrations cool the stratosphere, as the emission of thermal radiation in the direction of space is increased. And the loss of ozone also cools the stratosphere, as less incoming solar UV radiation is absorbed ”, Harald Rieder, head of the Institute for Meteorology and Climatology at the University of Natural Resources and Life Sciences (Boku) and co-author of the study, told APA. Because the troposphere is expanding due to global warming, the tropopause is also shifting upwards, where the air pressure is lower. “Above the tropopause it is exactly the opposite, the cooling contributes significantly to the shrinkage of the stratosphere and the stratopause (the border area to the next higher layer of the atmosphere, the mesosphere, note) decreases”, says Rieder.
Apart from the fact that it is noteworthy that previously unknown effects of climate change are still being discovered – the scientists suggest using the thickness of the stratosphere as another indicator of climate change – the phenomenon could have tangible consequences: the shifting of the atmospheric layers could also The authors of the study emphasize the effects on the trajectories and service life of satellites, the propagation of radio waves and the accuracy of global positioning systems such as GPS, which have yet to be investigated in detail. Source ORF.At