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Bad
news after good? –Recent Arctic stratospheric ozone losses
Rajendra
Shende, Head of OzonAction, UNEP speaks to NASA scientist and co-chair of the
Montreal Protocol Scientific Assessment Panel Dr. Paul Newman on 8th April 2011
The breaking news of record
losses of the stratospheric ozone over the Arctic and northern Europe, thereby
exposing large populations to the risk of elevated ultraviolet radiation (UV) is
quite unsettling and disquieting.
Rajendra
Shende requested Dr. Newman to briefly explain for the benefit of the National
Ozone Units around the world two recent and apparently contradictory
observations relating to levels of stratospheric ozone depletion. One report
appeared to be very positive; the other seemed to be a serious warning:
- The loss of stratospheric
ozone over Antarctica in September 2010 was one of the lowest on record.
- A record loss of stratospheric
ozone was recorded over the Arctic in March 2011.
The interview:
Mr.
Shende: “How should National Ozone Officers engaged in implementation of the
Montreal Protocol, which is considered to be a grand success, explain this
situation to their Ministers and their fellow countrymen?”
Dr.
Newman: “This low Arctic ozone is very interesting, but in the long term the
ozone layer will recover thanks to the Montreal Protocol. Without the Montreal
Protocol, this year’s ozone destruction would most likely have been worse. The
slow recovery of the ozone layer is due to the fact that ozone-depleting
substances stay in the atmosphere for several decades.”
Mr.
Shende: “It is stated that the loss observed is also due to the very low
stratospheric temperatures. What are the reasons for low temperatures?”
Dr. Newman: “The Arctic
stratosphere has been abnormally cold during March because of a lack of weather
systems. In a typical winter, we see a number of very large scale weather
systems that move upward from the lower atmosphere, the troposphere, into the
stratosphere. These weather systems warm up the Arctic during the winter and
spring. Surprisingly, these weather systems have been rather weak this winter.
The reason for the lack of weather systems is an area of active research.”
Mr.
Shende: “UNEP and WMO early this year released the ‘Report of 2010
Assessment of the Scientific Assessment Panel’ which provides an objective
synthesis of the impending recovery of Ozone Layer. How does this synthesis
match with these recent observations?”
Dr.
Newman: (emphatically) “This loss does not change the conclusion of Scientific
Assessment Panel that Arctic ozone will continue to increase as
chlorofluorocarbons (CFCs) decrease. The Montreal Protocol is an international
treaty adopted under the UN umbrella in 1987 to protect the ozone layer –
banning the production of ozone-depleting CFCs worldwide today. CFCs released
during prior decades however, will take many decades to disappear. Until that
time Arctic ozone levels are vulnerable, essentially depending on the
year-to-year variations in March-April Arctic stratospheric temperatures at
altitudes around 20 km.
It’s
like an upset of a great soccer team – events occasionally happen to cause a
great team to be poor while a poor team is great. In the end, it’s the entire
season that counts.”
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