Slight temperature shift in stratosphere could lead to massive Arctic ozone depletion
By Summit Voice
SUMMIT COUNTY — In yet another climate change paradox, warmer temperatures in the lower layers of the atmosphere may be cooling the high-elevation stratosphere, where researchers last year documented for the first time ever a massive hole in the ozone layer above the Arctic.
Researchers from the Karlsruhe Institute of Technology, who first discovered the Arctic ozone hole now say that the ozone layer may be at a tipping point.
“We found that further decrease in temperature by just 1 degree (Celsius) would be sufficient to cause a nearly complete destruction of the Arctic ozone layer in certain areas,” says Dr. Björn-Martin Sinnhuber, main author of the study.
Observations during the past thirty years indicate that the stratosphere in cold Arctic winters cooled down by about 1 degree Celsius per decade. Sinnhuber said further increases in carbon dioxide and other greenhouse gases will warm up the bottom air layers near the ground due to the reflection of part of the thermal radiation by the bottom layer of the atmosphere towards the earth’s surface, but also result in a cooling of the air layers of the stratosphere above, where the ozone layer is located.
In a chemical reaction already well-known from Antarctica, chlorine compounds originating from chlorofluorocarbons and other pollutants are converted chemically at temperatures below -78 degrees Celsius. These chemical conversion products attack the ozone layer and destroy it partly. One of the main statements in the study: If the trend to colder temperatures in the stratosphere observed in the past decades will continue, repeated occurrence of an Arctic ozone hole has to be expected.
After initial discovery of the Antarctic ozone hole in the mid-1980s, CFCs were rapidly identified to be the cause and their use was prohibited by the Montreal Protocol of 1987. However, it will take decades until these substances will have been removed completely from the atmosphere.
“Future cooling of the stratosphere would enhance and extend the impacts of these substances on the ozone layer,” Sinnhuber said.
The studies continued this year with flights in northern Sweden, where the researchers again detected extraordinarily low temperatures. However, they said they can’t yet predict whether temperatures will be low enough over a longer term to cause a comparably large degradation of ozone in this winter.