The sky isn’t falling, but scientists have found that parts of the upper atmosphere are gradually contracting in response to drastic human-made greenhouse gas emissions.
Combined data from three NASA satellites have produced a long-term record that reveals the mesosphere, the layer of the atmosphere 30 to 50 miles above the surface is cooling and contracting. Scientists have long predicted this effect of human-driven climate change, but it has been difficult to observe the trends over time. Study was published in the journal Science Direct.
The lead author of the study, Scott Bailey, an atmospheric scientist at Virginia Tech said, “You need several decades to get a handle on these trends and isolate what’s happening due to greenhouse gas emissions, solar cycle changes, and other effects”.
Together , the satellites provide about 30 years of observations, including that the summer mesosphere over Earth’s poles is cooling four to five degress Fahrenheit and contracting 500 to 600 feet per decade. Without changes in human carbon dioxide emissions, the researchers expect these rates to continue.
“Down near Earth’s surface, the atmosphere is thick ,” said James Russell, a study co-author and atmospheric scientist at Hampton University in Virginia. “Carbon dioxide traps heat just like a quilt traps your body heat and keeps you warm”. In the lower atmosphere, there are plenty of molecules in close proximity, and they easily trap and transfer Earth’s heat between each other, maintaining that quilt-like warmth.
A major cause of concern is the growing threat to satellites as atmospheric gases cause satellite drag, the friction that tugs satellites out of orbit and helps clear space junk. As the mesosphere contracts, the rest of the upper atmosphere above sinks with it, which can lead to a decline in the drag and an increase in space junk.
Though what happens in the mesosphere doesn’t directly impact humans, the region is an important one. The upper boundary of the mesosphere, about 500 miles above Earth, is where the coolest atmospheric temperatures are found. It’s also where the neutral atmosphere begins transitioning to the tenuous, electrically charged gases of the ionosphere.