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Record Low Temperatures in
Arctic Ozone Layer - First Signs of Ozone Loss
28 January 2005
Press Release
Record low temperatures in Arctic ozone layer - first signs of ozone loss
The first signs of ozone loss have now been observed in the Arctic this winter, and large scale
losses are expected to occur if the cold conditions persist. Overall temperatures in the ozone
layer are the lowest for 50 years having been consistently low for the past two months.
Since late November large areas of polar stratospheric clouds (PSCs)- clouds in the ozone
layer- have been present over the Arctic region at altitudes around 20km. They are now the
largest in the last 20 years, the period when the ozone-depleting compounds have been high.
These conditions could make ozone depletion very likely.
The chemical balance in the stratosphere is changed significantly by the presence of these
clouds, altering the breakdown products from CFCs (chlorofluorocarbons) so that rapid
chemical ozone destruction can occur in the presence of sunlight. If the Arctic stratosphere
remains cold during February and March, large ozone loss is expected to take place as
sunlight returns to northern latitudes. This could lead to increased levels of ultraviolet
radiation in inhabited areas in the northern part of Europe.
Scientists from the EU SCOUT-O3 Integrated Project have been studying the links between
stratospheric ozone and climate change in the Arctic since May 2004, with the aim of
providing predictions of future ozone and other stratospheric changes as well as the associated
UV and climate impact. The project is co-ordinated at the University of Cambridge’s
Department of Chemistry and has 59 partner institutions with over 200 scientists involved
from 19 countries.
The scientists are following the situation in the Arctic closely using a combination of
measurements and atmospheric models. Measurements from the ground-based network of
atmospheric observing stations and from satellites are being combined to investigate the
ozone loss in the coming weeks.
The extreme conditions are of major concern and scientists will be addressing a number of
questions: How large will the ozone loss be? What will be the impact on UV radiation? Are
the conditions more favourable for large ozone losses than before?
“The meteorological conditions we are now witnessing resemble and even surpass the
conditions of the 1999-2000 winter- when the worst ozone loss to date was observed,” said
Dr. Neil Harris of the European Ozone Research Coordinating Unit, Cambridge, UK, and one
of the coordinators of the SCOUT-O3 project.
“However, it is still too early to predict the temperature development in February and March,
which are the crucial months for ozone loss in the Arctic. We will watch the development
closely from day to day, and will inform the public and our authorities if the situation
becomes worrying,” concludes Dr. Harris
The cold conditions have worsened during the month of January, and in the last few days the
geographical extent of PSCs has reached values which are much larger than ever observed in
the Arctic.
“Preliminary analysis of data from the international ozonesonde network shows the first signs
of depletion at around 20 km altitude. Given the unusual situation we have intensified the
measurements. It is not yet clear how the ozone layer will respond to the cold conditions, but
we will find it out.” said Dr. Markus Rex, from the Alfred Wegener Institute for Polar and
Marine Research, who coordinates the Arctic ozone loss studies in SCOUT-O3.
“Overall, measured by the extent and persistence of conditions for PSC formation, the
situation is now colder than anything I have seen in the Arctic before. In particular, the large
extent of ice clouds gives reason for concern,” added Dr. Rex.
SCOUT-O3 is a 5 year project receiving 15 million euros from the European Commission
Research DG’s Global Change and Ecosystems Programme and a similar amount of
associated funding from national agencies. More information on the SCOUT-03 project
can be found at: www.ozone-sec.ch.cam.ac.uk
The degree of Arctic ozone loss varies greatly from year to year. For example, there were
losses of <10% in 1998/99 and >65% in 1999/2000 at altitudes around 18 km, and losses
of 50% or more have been seen at around 18 km in several winters since the early 1990s.
Chemical losses in the total column of ozone over the Arctic have varied between about 5
and 30% since the early 1990s. Overall a decrease in total ozone in the Arctic region has
been observed since 1980, although there is considerable year-to-year variation in the
observed values. This variability in the ozone loss is to be contrasted with the Antarctic
where nearly complete ozone loss has taken place in all except one winter since the late
1980s at altitudes between about 15 and 20 km.
The use of halogen-containing substances, such as chlorofluorocarbons (CFC) and halons
has led to an increase in the atmospheric concentration of chlorine and bromine. The
substances can cause ozone depletion. The destruction of the ozone layer by man-made
chlorine and bromine is most effective under very cold conditions. Rapid ozone loss can
occur when temperatures drop below about -78°C, a value that is sometimes reached in
the Arctic ozone layer at about 20 km altitude in winter. Since ozone destruction also
requires sunlight, the ozone loss process starts after a cold winter when the sun returns to
polar latitudes in spring.
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