The study, published in Science Advances, is based on decades of weather balloon observations and specialized satellite measurements to determine the extent to which the peak of the atmosphere rises. This area, the tropopause, raises the boundary of the stratosphere by about 50 to 60 meters (about 165 to 195 feet) in a decade.
The rise is due to warming temperatures near the earth’s surface, causing the lower atmosphere to expand.
“This is a clear sign of the changing structure of the atmosphere,” he said Bill Randel, A researcher at the National Center for Atmospheric Research (NCAR) and co-author of a new study. “These results provide independent confirmation of all other evidence of climate change, in addition to the fact that greenhouse gases are changing our atmosphere.”
The international research team was led by researchers from Nanjing University in China. The research was supported in part by the National Science Foundation, which is a sponsor of NCAR.
The altitude of the tropopause, the region of the atmosphere that separates the dense and turbulent troposphere from the more stable stratosphere, varies about 5 miles above the Earth’s surface at the poles 10 miles at the equator, depending on the season.
The location of the tropopause is of interest to commercial pilots, who often fly in the lower stratosphere to avoid turbulence, and plays a role in severe thunderstorms, the excess of which sometimes drives the tropopause higher and draws air from the stratosphere.
The steadily rising height of the tropopause in recent decades does not have a significant impact on society or ecosystems, but it does describe the far-reaching effects of greenhouse gas emissions.
Previous scientific studies have shown that the tropopause is increasing. This was due not only to climate change but also to the cooling of the stratosphere associated with ozone depletion. However, the 1987 Montreal Protocol and subsequent international agreements to limit emissions of ozone-depleting chemicals have successfully reversed ozone depletion and stabilized temperatures in the lower stratosphere.
Randel and his authors recently collected available data to analyze how much the tropopause continues to rise now that stratospheric temperatures no longer have a significant effect.
They turned primarily to two sources of information. One of them was a recently updated archive of observations of radiosondes that have been lifted high into the atmosphere for decades to measure the properties of the atmosphere.
Because radiosonde data are most detailed in the northern hemisphere between 20 and 80 degrees latitude, new research focused on the rise of tropopause in this region.
The researchers also analyzed observations from specialized satellite instruments dating back to 2002 that study the atmosphere by measuring the extent to which Global Positioning System (GPS) radio signals bend and decelerate as they pass through the atmosphere.
This innovative technology, known as GPS radioculture, was pioneered by a number of satellites known as COSMIC (now COSMIC-2), whose data are processed and shared by the University Corporation for Atmospheric Research, which manages NCAR.
The research team then used statistical techniques to account for the effects of natural phenomena that temporarily alter atmospheric temperatures and affect the tropopause, such as volcanic eruptions and the occasional warming of surface waters in the eastern tropical Pacific Ocean known as El Nino. This allowed them to isolate the role of man-made warming.
Analysis of their radiosonde observations showed that the height of the tropopause has risen steadily since 1980: about 58-59 meters per decade, of which 50-53 meters per decade is due to man-made warming of the lower atmosphere.
This trend has continued, although the impact of stratospheric temperatures has weakened, indicating that warming in the troposphere is having an increasing impact.
Satellite observations since 2000 have confirmed that the height of the tropopause has risen over the past two decades.
“The study finds two important ways people change the atmosphere. Greenhouse gas emissions are increasingly affecting the height of the tropopause, although society has successfully stabilized stratospheric conditions by restricting ozone-depleting chemicals,” Randel said.
Source: The Nordic Page