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European Ozone Research Coordinating Unit (EORCU)
European Commission (EC) research programmes encouraged collaborative projects involving research groups in different countries. This approach particularly suited the global problem of ozone depletion.
Most stratospheric ozone research in Europe had traditionally been carried out with funding from national sources. Several years ago scientists from many of the European Union (EU) and European Free Trade Association (EFTA) countries suggested that a small group be set up to coordinate stratospheric ozone research in Europe from both the national research programmes and the European Union research programme.
EC stratospheric research activities were undertaken in conjunction with research programmes of individual countries and in liaison with the World Meteorological Organisation (WMO) and the United Nations Environment Programme (UNEP). They contribute to a continuing scientific assessment of the causes and the consequences of stratospheric ozone depletion. This is an obligation under the Vienna Convention and the Montreal Protocol on Substances that Deplete the Ozone layer, to which the European Union and its member states are party.
EU and EFTA ministers agreed in October 1987 to take steps to coordinate such research, and at a meeting in The Hague in 1988 agreed the final form of the coordination group or 'Science Panel' to be set up. Part of the Science Panel was to be a small, permanently staffed unit which would review existing European national programmes, prepare research plans and provide advice where required. The European Ozone Research Coordinating Unit was also set up to manager, administer, organise and coordinate this work.
Since 2004, changes in the structure of EC funded European Ozone Research has resulted in the funding of large integrated projects which coordinate atmospheric science within specific themes. As such the need for the Science Panel fell away, and EORCU now coordinate the Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere (SCOUT-O3) Integrated Project.
While ozone can be measured throughout much of the atmosphere, most of it is found in the stratosphere in a layer centred about 20 km above the earth's surface. Ozone is beneficial to life on earth because it blocks much of the dangerous ultraviolet light (UV-B) radiated by the sun. If this UV-B reaches the earth's surface, it harms most forms of life. For instance, it can cause skin cancers in humans and may reduce crop yields. But for over a decade the ozone layer has been thinned by man-made halogen-containing compounds such as CFCs and halons, the halogens in question being chlorine and bromine.
What has happened to the
Ozone Layer?
In 1985 the Antarctic ozone
hole was first reported: losses in total ozone of more than 50% had occurred
in October (the Antarctic spring) in the previous few years, and have continued
to occur each year since. Satellite data now show that ozone losses between
1979 and 1995 have occurred more widely. For example, in March, average ozone
amounts between 35° and 55°N have decreased by more than 12% over
these 16 years. Measurements show that in 1992/93 ozone amounts were less
than in any previous year on record, both globally and in the Antarctic ozone
hole. In 1994 Antarctic ozone amounts had recovered slightly and were back in
line with the longer term decline. During 1996, record low ozone amounts were
observed over Europe and measurements for 1997 already indicate that substantial
ozone loss has occurred. This is because the recent Arctic winters have been
particularly cold and undisturbed when compared with earlier years.
What are the ozone depleting
chemicals?
Chlorofluorocarbons (CFCs)
and halons, along with carbon tetrachloride and methyl chloroform are the primary
man-made ozone depleting chemicals. The transitional replacements for CFCs,
the HCFCs, also have some ozone depleting potential. Chlorofluorocarbons have
had many uses, e.g. in refrigerators and air conditioners and as industrial
solvents. They have been used in every country in the world. Halons are used
as fire retardants. Wherever these substances are released, they spread throughout
the atmosphere and are eventually carried up into the stratosphere. They have
long lifetimes and will remain as a threat to the stratosphere for much of the
next century.
Stratospheric aerosols and
ozone
Located some 10 km
higher than rain clouds, stratospheric aerosol consists of clouds of ultrafine
droplets, consisting of a mixture of water and sulphuric acid. Some aerosol
is transported there from the lower atmosphere by the winds, but occasionally
volcanic eruptions inject large amounts of sulphur dioxide into stratosphere,
forming more sulphuric acid. Under very cold conditions the aerosol droplets
promote the destruction of ozone by permitting the release of halogens from
passive forms and by mopping up some of the chemicals that convert halogens
back into their passive forms after they have been activated for ozone destruction.
In 1991 the eruption of Mt Pintubo injected large amounts of aerosol into the
stratosphere, resulting in significantly enhanced ozone destruction through
1992 and 1993. Aerosols amounts have since returned to normal.
How is ozone depleted?
Ozone is a molecule made
from three oxygen atoms. Its concentration depends on a balance between production
and destruction processes. Production occurs when ultraviolet light breaks down
oxygen molecules, leading to the formation of ozone. Destruction involves chemical
reactions with nitrogen, hydrogen, chlorine and bromine compounds. Chlorine
and bromine are released in the stratosphere when the CFCs and halons are broken
down by ultraviolet light. Thus production is driven by the sun while destruction
depends on the concentration of a number components, some of which have been
building up in the atmosphere.
On average each chlorine atom released into the stratosphere will destroy over a thousand ozone molecules. During the 1980's as much as 0.5 million tonnes of CFCs were released each year and the cumulative CFC loading peaked at 30 million tonnes. About one in sixty CFC and halon molecules reaches the stratosphere where it can release halogens. The atmosphere contains some 9 000 million tonnes of ozone.
Chlorine is found in both so-called active and passive forms. The active chlorine compounds are directly involved in ozone depletion. The amount of active chlorine determines the degree of ozone depletion.
The very cold temperatures (about -80°C) which occur in the polar stratosphere in winter cause polar stratospheric clouds to form from water vapour and aerosols. Chemical reactions take place on these cloud particles and aerosol droplets which convert halogens from passive to active forms. Rapid ozone destruction follows when sunlight returns.
High levels of chlorine monoxide (one of the active forms of chlorine) were measured in the ozone hole over Antarctica in 1987. Low levels of ozone were found where there were high concentrations of chlorine monoxide. Considered with other data, these measurements proved that chlorine and bromine compounds had caused the ozone hole.
In the Arctic stratosphere in January/February 1989, and again during the 1991/92 EASOE campaign, chlorine monoxide concentrations were found to be as high as in the Antarctic ozone hole. The Arctic stratosphere was therefore primed for ozone depletion.
The wintertime meteorologies of the two polar regions are very different, with the atmosphere more disturbed in the north and with temperatures lower in the south. This accounts for differences in ozone depletion between north and south. But recent Arctic winters have been considerably colder and less disturbed than normal and this is likely to have been responsible for the enhanced ozone loss observed recently. There is concern that this may be a result of a feedback from ozone depletion which directly results in stratospheric cooling or from interactions with climate change.
In the Northern Hemisphere no ozone hole has been reported, but observations during SESAME showed total ozone values as much as 40% below normal with losses of up to 60% at altitudes around 18 km. During the winter of 1994/95 low ozone was measured as far south as Aberdeen and simultaneous measurements detected high chlorine monoxide levels.
The cause of the decline in ozone in the middle latitudes of both hemispheres is now qualitatively understood and it is clear that halogen compounds are responsible for some of the observed changes. It also seems likely thatchanges in the transport of ozone have played some part in accounting for the observations. Results from EASOE and SESAME are helping to answer these questions, and THESEO will investigate further investigate the problem.
A wide variety of instruments were used during EASOE and SESAME in order to understand the processes which influence the stratospheric ozone in the Arctic region.
Research Balloons: Instruments were flown on research balloons to make in situ measurements of trace chemicals in the stratosphere; 43 balloon flights were launched from Kiruna, northern Sweden. Ground-Based Instruments: Twenty stations have been involved in ground based measurements of chemical composition at locations near the Arctic Circle and in northern Europe.
Aircraft: Three aircraft flew 100 missions during EASOE to determine the distributions of a wide variety of trace species. The mobility of aircraft allows considerable flexibility in planning experiments. Five aircraft were used during SESAME.
Ozone sondes: Ozone concentration is measured routinely at many locations using small balloons carrying lightweight ozone sensors. Ozone sondes were launched 2 or 3 times weekly giving unprecedented coverage of the Arctic stratosphere in winter. In all, 1,000 launches were made during from 20 stations during EASOE and 2,000 during SESAME from 26 stations.
Modelling: Numerical models of the chemical and physical processes occurring in the Arctic stratosphere aid interpretation of the measurements and helped the planning of balloon launches and aircraft flights. Meteorological data was provided by the European Centre for Medium-Range Weather Forecasts and the UK Meteorological Office. Some of this forecast data was used to forecast the chemical composition of the atmosphere during the SESAME campaign.
Many of the results of EASOE are published in a special issue of Geophysical Research Letters (June 22, 1994, Vol. 21, No. 13) containing over 70 scientific papers. They include measurements of the important chemical species involved in ozone destruction and analyses of the interplay between the dynamic motions of the stratosphere and the chemistry which occurred. For instance, it is clear that there was a large region of air over the Arctic in which the chlorine had been activated. EASOE studies have show that the ozone loss in the Arctic vortex, measured in the experiment, is consistent with the chlorine activation. Other studies are providing important clues to the reasons for the middle latitude ozone decline. These results were an important part of the European contribution to the 1994 UNEP/WMO Scientific Assessment of Ozone Depletion.
The results of SESAME are currently the subject of a series of special sections of the Journal of Atmospheric Chemistry. Stratospheric weather conditions during SESAME were more conducive to ozone loss than during the EASOE campaign. The use of forecasting methods also meant that the greater resources applied during SESAME were very effectively utilised. Measurements during SESAME directly observed ozone loss in the Northern hemisphere for the first time and losses of up to 50% at around 18 kilometers altitude were found inside the Arctic vortex. They also confirmed the discrepancy between observed nitrogen species and those calculated by computer models. On the other hand, the models were generally found to accurately estimate amounts of chlorine monoxide. Many of the questions posed by the results gathered from the EASOE and SESAME campaign are being tackled directly by THESEO.
In 1978 the United States, Canada, Belgium, Norway and Sweden banned the use of CFCs as propellants in aerosol cans. The countries of the European Community adopted measures to reduce CFC use in aerosols by 30% from 1976 levels, and agreed not to increase their CFC production capacity. Australia reduced CFC use in aerosols by 66%
Despite efforts by UNEP and the signing in 1985 of the Vienna Convention on the Protection of the Ozone Layer attempts to obtain concerted international action failed, and rapid growth in non-aerosol uses of CFCs took emissions of CFCs to record levels during the 1980s.
Not until substantial losses of ozone had been reported in 1985 did the situation change. The Montreal Protocol was negotiated in September 1987, and obtained enough support to come into effect on 1 January 1989. By signing this Protocol, countries agreed to limit future emissions of CFCs and Halons. However, the controls proved insufficient to stabilise atmospheric concentrations of CFCs, let alone reduce them.
In 1990 in London the provisions of the Montreal Protocol were considerably tightened to require a complete phase-out of CFCs and Halons by the year 2000. Agreement was also reached to phase out 1,1,1 trichloroethane and carbon tetrachloride.
In November 1992, the parties to the Montreal Protocol met again, in Copenhagen. Further revisions to the Protocol were agreed. The production and supply of controlled substances would be considerably reduced after 1 January 1994, bringing the phase-out dates forward. New controls on HCFCs and methyl bromide were introduced. The EU adopted even stricter controls with phase-out of CFC production and consumption (i.e. production plus imports minus exports) from January 1995.
The most recent meeting of the parties to the Protocol, at Vienna in 1995, acted to tighten the controls on the consumption of HCFCs and methyl bromide.
The results of these efforts were seen in 1996 when the first signs of a decrease in the amount of ozone destroying chemicals was observed in the lower atmosphere. According to the current understanding, the ozone will not begin to recover for another decade, finally returning to normal around the middle of the next century.
Large Scale Scientific Field Campaigns
European Arctic Stratospheric
Ozone Experiment (EASOE)
The first major task EORCU was the coordination of a large scale field campaign, EASOE,
which was composed of research projects under the EC ENVIRONMENT Programme.
The campaign aimed to understand the causes of the observed ozone losses in
the Northern Hemisphere. From November 1991 to March 1992 over 60 research groups
(mainly from Europe, with a few from the USA, the USSR and Japan) performed
experiments to investigate the Arctic stratosphere. EASOE scientists made a
large number of measurements of ozone and other important chemicals throughout
the winter and have subsequently carried out analyses of these data. A major
collection of scientific papers from EASOE, edited by the EORCU, appeared in a special
issue of Geophysical Research Letters in June 1994.
Second European Stratospheric
Arctic and Mid-latitude Experiment (SESAME)
EORCU played an important part in the second major European field campaign,
SESAME. This campaign was composed of 15 projects in the framework of the EC ENVIRONMENT
Programme, along with some participation by non-EU states, and took place between
January 1994 and December 1995. Direct field measurements consisted of balloon
launches, scientific aircraft flights, ground based remote sensing of atmospheric
composition and some satellite measurements. Field measurement planning was
assisted by forecasting using chemical models and complimented by similar diagnostic
studies in the subsequent data analysis. These were further refined by laboratory
measurements to precisely examine the parameters of stratospheric chemical reactions.
In addition to the polar studies, SESAME examined the middle latitudes where
long term ozone depletion has also been observed. The scientific results of
SESAME became the subject of a series of special sections in the Journal
of Atmospheric Chemistry whose preparation EORCU managed.
Third European Stratospheric
Experiment on Ozone (THESEO)
EORCU was involved
in the early planning of THESEO, the third European measurement campaign. It
operated from winter 1997/98 to December 2000. EORCU helped pan-European
collaboration by hosting large scale planning meetings and assisted in the effective
preparation of scientific proposals, in particular by facilitating communication
between scientific partners throughout EU member states. THESEO was funded
under the Environment and Climate section of the European Union's Framework
IV programme, and by national science programmes.
Validation of INTERnational
Satelites and study of Ozone Loss (VINTERSOL)
EORCU was involved in planning and organisation of VINTERSOL, a major European field campaign studying stratospheric ozone which took place from late 2002 until mid 2004. It was the latest of the major European field campaigns to study ozone loss and was funded jointly from national funding agencies and the Environment and Sustainable Development programme of EC DG Research. VINTERSOL examined the chemical and physical processes associated with stratospheric ozone depletion at Arctic and neighbouring mid-latitudes. The campaign consisted of EC and nationally funded research projects with interest in validating satellite instruments such as those on ERS-2, ODIN and ENVISAT. These activities involved a variety of ground-based, balloon-borne, and aircraft-borne instruments coupled with comprehensive modelling activities.