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 20
kilometres. 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.
Notes for Editors:
1. For photographs
contact University of Cambridge Press and Publications Office.
2. 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
3. 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.
4. 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.
5. More information on
the ozone layer problem can be found at: Ozone Hole Tour:
http://www.atm.ch.cam.ac.uk/tour/index.html
UN Environment Programme:
http://www.unep.org/ozone/index.asp
World Meteorological
Organisation: http://www.wmo.ch/indexflash.html
For more information,
contact:
-
1. Corina
Hadjiodysseos, Press and Publications Office, University of
Cambridge, UK Tel: 01223 332399; email: ch250@cam.ac.uk
2. Dr. Neil Harris,
Department of Chemistry, University of Cambridge, UK Tel: 01223
311797; email: Neil.Harris@ozone-sec.ch.cam.ac.uk
3. Dr Markus Rex,
Alfred Wegener Institute for Polar and Marine Research in Potsdam,
Germany Tel: + (49) 331 288 2127; email: mrex@awi-potsdam.de
