Are greenhouse gas emissions shrinking the stratosphere?
Relax. Contrary to some reports climate change is not going to cause satellites to fall out of orbit or your satnav to malfunction.
According to scientists led by Charles University in Prague writing in a paper just accepted by the journal Environmental Research Letters the stratosphere is shrinking. They say they have found a “substantial contraction” since 1980, the date when measurements commenced. Since then it has shrunk by 400 metres at a fairly constant rate of about 100 metres a decade. It’s obvious that the decline predates 1980 so the cause is likely not due to recent environmental changes. See Fig 1.
Substantial? Not in my book. Remember that the stratosphere – the atmosphere’s second major layer sandwiched between the troposphere and the mesosphere – starts at an altitude of 35,000 metres (at the equator, lower at higher latitudes) so it’s a small change and not an “alteration to the equilibrium of the planet” as has been stated.
Satellite operators need not be worried. Satellites orbit high above the region where these effects are seen in the thermosphere (90-600 km) where the atmosphere is chiefly under the influence of the Sun. Typically a satellite will decrease its orbit by 5 metres a day when the solar activity is low but up to 50 metres a day when it’s high. Hence the need for regular reboosting of the International Space Station.
The researchers say that the overwhelming cause of the decline in the size of the stratosphere is down to increasing greenhouse gas emissions and they have the output of a computer model to prove it. I suspect that given that the size of the stratosphere has declined slightly and greenhouse gasses are increasing a computer model could assign causation though given the data inputted into the model I am unconvinced.
The researchers go further making extrapolations to 2080 saying that by that time the stratosphere will have shrunk by a total of 975 metres. As 2080 is far further away than the length of the data already obtained I think that’s a watching brief.