SCOUT-O3 Overview

Background
The central aim of the SCOUT-O3 project is to provide scientific knowledge for global assessments on ozone depletion and climate change for the Montreal and Kyoto Protocols. European countries and the European Union (EU) have a responsibility under: the Montreal protocol of the Vienna Convention; the UN Framework Convention on Climate Change; and the Kyoto Protocol.

The Montreal Protocol has successfully reduced emissions and atmospheric concentrations of CFCs, which are estimated to return to their pre-ozone hole concentrations by about 2050. The Kyoto Protocol was the first international measure to put a restraint on the galloping rise of carbon dioxide (CO₂) emissions caused by industialised nations.

However, the ozone layer is unlikely to return to its pre-ozone hole state by 2050 and so the remaining central question for the Montreal process is: “How and when will ozone and UV radiation recover as CFC concentrations fall?”. The answer is required within the next few years, in order to provide essential advice to European policy makers.

Knowledge about the state of the atmosphere and the processes that govern it, constitute the basis for political negotiations and decisions concerning the phase-out of ozone depleting substances and greenhouse gases emission limits.

SCOUT-O3 contributes to this knowledge, which is necessary to formulate a sound environmental protection policy. The improvement of computer models (a central goal of the project) is necessary for the prediction of future ozone loss. Such predictions will have implications for community policies on the phase-out of ozone depleting substances.

Results from SCOUT-O3 will form important European input to international assessments, such as the Intergovernmental Panel on Climate Change (IPCC), whose fourth assessment report is currently being planned (for 2007). An IPCC/TEAP report on ‘Safeguarding the ozone layer and the global climate system’ is planned to appear in 2005; SCOUT-O3 and SCOUT-O3 scientists are making major contributions to this report. We will also contribute to the next World Meteorological Organisation (WMO)/UNEP stratospheric ozone assessment, planned for 2006-07.

The SCOUT-O3 project aims to provide new knowledge for EU and national governments, which could be used to develop the European position for sustainable development. SCOUT-O3 involves the research efforts of 59 partners with more than 100 scientific groups; and takes full advantage of new and existing research facilities developed at a national level.

Science
The state of the ozone layer over the next decades will depend on the interplay between climate change and the impact and evolution of ozone depleting substances, such as CFCs. The strengthening of the European predictive capability through improving the use of coupled chemistry/climate models (CCMs) will provide an improved understanding of model performance that will be gained from on-going validation and comparisons from existing and new measurements.

The integration of process studies within a modelling framework will enable SCOUT-O3 to analyse and predict the current status and future evolution of the ozone layer and surface ultra violet (UV) levels with high confidence.

Measurement interpretation will be achieved using a variety of models operating on all spatial scales.

Denitrification in the polar vortices is being studied to remove one of the major uncertainties regarding polar ozone loss.

Better understanding of processes in the upper troposphere and lower stratosphere (UTLS) through modelling and data analysis, and studies of the long-term variability in extratropical large scale transport are also being performed to improve long-term predictions of mid- and high latitude ozone and UV.

Past and present variability in UV radiation is determined using re-evaluated and quality controlled data sets. Focused studies involving measurements and modelling are used to improve understanding of how clouds and aerosols modify atmospheric radiation.

A comprehensive range of scenarios will be used in CCMs to provide the basis for a comprehensive study of the evolution and feedback of the coupled chemistry/climate system.
Our appreciation of the wide-ranging importance of chemistry/climate feedbacks developed considerably during the last decade. This is now seen as a crucial component of the ‘earth system’ and one where further progress is essential for successful prognoses of the future development of the system. SCOUT-O3 is making a major contribution to global change studies by concentrating on these chemistry/climate issues.

Lack of knowledge about the tropical stratosphere and upper troposphere is addressed through tropical field campaigns involving aircraft and balloons to investigate detailed mechanisms by which air passes from the troposphere to the stratosphere. New fundamental information about chemical and microphysical processes gained from laboratory studies will improve models used to interpret these measurements. Understanding of the larger scale importance is gained through analysis of satellite measurements (e.g. from ENVISAT and CALIPSO), meteorological analyses and other global fields.