S P A R C Stratospheric Processes And their Role in Climate A project of the World Climate Research Programme Home Initiatives Organisation Publications Meetings Acronyms and Abbreviations Useful Links

A Short History of the Beginning of SPARC and its Early Development

Marie-Lise Chanin, SPARC Office, Verrières le Buisson, France (chanin@aerov.jussieu.fr)

The genesis of any project requires years of efforts by a community of scientists, first to formulate the issue and then to have it accepted by the main international scientific organisations. In the process which led to the recognition of SPARC as a project of WCRP, a number of scientists were involved in different ways. It is impossible to mention all of them, without taking risk to be incomplete, but I would like to associate the name of M. Geller as a main actor in all of these attempts, which led to the project as it has developed, and to thank all the others for their active support.

The Recognition of SPARC as a WCRP Project

The issue of ozone depletion had raised an enormous interest in our community since the middle of the 70’s, and even more after the discovery of the ozone hole in 1984. Many important national programmes were set-up and there was no need to create new ones on the same issue. However, in the early 90’s, the stratosphere was barely mentioned as a region of interest in the thematic of the two main International Global Change Programmes of ICSU: WCRP, which dealt with the physical aspect of the climate, and IGBP, which had just been created in 1986 to study the interactive physical, chemical and biological processes that regulate the total Earth System. The issue of the stratosphere, or to be more precise of stratospheric ozone, was considered as completely separate from the climate issue. As a matter of fact, it has been true for quite a long time that the WMO-UNEP Scientific Assessments on Ozone Depletion were carried out completely independently of the IPCC Assessments. This is no more true today and outputs of the first one are being taken into account in the later.

On the other hand at that time, tropospheric chemistry had received a full recognition within the IGAC Project first created by the International Commission of Atmospheric Chemistry of IAMAP and later in the late 80’s accepted as an IGBP Core Project. However, the issues covered by IGAC dealt exclusively with the troposphere and did not include the complex interactions between chemistry, radiation and dynamics, which characterise the tropopause region and the stratosphere.

Two main organisations prepared the way for the recognition of the role of the stratosphere in the climate. First, the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) which, after the very successful Middle Atmosphere Programme (MAP) in the 1980’s, included in its following Programme STEP (Solar Terrestrial Energy Programme) a topic entitled “Middle atmosphere response from above and below”. The relevant W.P. 4 led by M. Geller and myself had a large influence on the scientific content of SPARC. I should also mention that it included the issue of “Solar variability effects on the environment” as the theme of W.G. 5 of STEP under the leadership of K. Labitzke; this issue was picked up later on by SPARC and is still a theme of joint interest between SCOSTEP and SPARC.

During the same period, the role that the International Union of Geophysics and Geodesy (IUGG) should play in IGBP was being discussed; a proposal was elaborated at the end of the 80’s, mostly by a group of scientists from two of the IUGG Associations, IAGA, IAMAP (now IAMAS), and of its joint Commission on Middle and Upper atmosphere ICMUA, (which later became ICMA). This programme was elaborated and proposed in 1988 to be implemented by IGBP under the name of MARC (Middle Atmosphere Responses to Changes). But it was not accepted as an IGBP Project.

Meanwhile, as a member of the first Scientific Steering Committee (SSC) of IGBP established in 1987, I tried to find a way to include the stratosphere in the IGBP Programme. The Project STIB (Stratosphere-Troposphere Interactions and the Biosphere), which emerged after several workshops (Abington, UK, January 1990 and Stony Brook, USA, June 1991), took into account the specific interest of IGBP and, therefore, placed the emphasis on the impact of ozone depletion on the biosphere. STIB was concerned with the way biogenic and anthropogenic emissions change the composition, radiation and dynamics of the stratosphere and how those changes affect the biosphere. The topic of the biosphere impact of UV radiation essentially disappeared later from SPARC, due to the fact that it concerns actually a quite different community. The other themes in the proposal were very close to what was included in the future SPARC. The refusal of STIB by IGBP in 1991 led to a revision of the proposal and to the acceptance of SPARC by WCRP in March 1992. We were fortunate to have scientists who were themselves distinguished middle atmospheric researchers in the Joint Scientific Committee (JSC) and in the Joint Planning Staff (JPS). Thanks to all of them and to the Executive Director, P. Morel, for whom it was surely quite a revolution to introduce Chemistry in the fortress of Physics. The development of SPARC within WCRP has in fact been a wonderful experience and R. Newson, who, until his recent retirement, has been our permanent contact with the JPS of WCRP, is to be thanked for his constant support during the first decade of SPARC.

The Development of SPARC

The first main meeting of the very young SPARC Project took place in September 1992 in Carqueiranne, in the South of France, as a NATO ASI, which I organised with a group of lecturers who played a main role in the definition of SPARC priorities and in the write-up of a WCRP Report entitled “Initial Review of Objectives and Scientific Issues”, published in 1993.

The composition of the first SSG was decided at the March 1993 JSC-WCRP meeting and the selection of its members had a strong influence on the development of the project. It included to assist the 2 Co-Chairs, M. Geller and myself: D. Ehhalt, I. Isaksen, V. Khattatov, J. Mahlman, T. Matsuno, J. Pyle, T. Shepherd, S. Solomon, H. Tanaka and R. Turco. Its first meeting took place in 1993 in Corpus Christi College, Cambridge, UK.

I would like to mention some principles, which we kept in mind continuously during the development of the project. A first important rule, which I, with M. Geller and the SSG members tried to respect all along, was not to include in SPARC the topics that were ongoing in other existing programmes. That meant essentially that we established strong links and good relationship with the national “ozone depletion” programmes, without walking in their path but rather looking for areas that needed more concerted efforts. This approach worked very well, thanks to a few key people, who recognised that SPARC was not a threat but a complement to their activity. A second rule was to anticipate areas where better knowledge of the stratosphere could contribute; this led to a successful activity of assessments of our current knowledge of key quantities (temperature, ozone vertical profile, water vapour concentration, aerosols as well as the contribution of the stratosphere to radiative forcing), which were and are still needed for the larger enterprises of WMO-UNEP and IPCC assessments. Those exhaustive assessments required the participation of hundreds of scientists and played an important role in the recognition of the role of SPARC.

Most of them are published as SPARC Reports.One main characteristic in running the project and which could not have been able to decide in advance, even though we could have wished it to be, has been a constant feature of SPARC leadership all along those years: it is the wonderful sense of community within the enlarged leading group, which includes, beside the co-Chairs and the SSG members, the ex-officio members of the SSG and the activity leaders, all of them working in a very friendly and cheerful atmosphere. This, I have to admit, is the best reward that one can have when devoting one’s energy for the success of any project.

When thinking of the way the role of the stratosphere in the climate issue was perceived 12 years ago compared to the present situation, I feel that a large step has been made during that period. Just to mention a few examples: most GCMs are now including the stratosphere with a more or less sophisticated chemistry, as the demonstration was made that it plays an important role in the way the troposphere behaves. Models are also starting to benefit from a better parametrisation of gravity waves, a subject in which SPARC has been intensively involved. The representation of the Quasi-Biennial Oscillation (QBO) in the models has been improved. The connection between the stratospheric Northern and Southern Annular Modes and the surface, which has been recently discovered, is obviously confirming the idea that the coupling between stratosphere and troposphere cannot be ignored. Another very controversial issue a decade ago was the way the solar variability influences the climate: it is now a subject taken without passion and the role of the stratosphere in the process through the UV absorption by ozone starts to be well accepted. The perception of the tropopause, not only as a barrier between two regions of the atmosphere, but also between two scientific communities is now starting to disappear; our newly developed joint-project with IGAC is a symbol of this situation (see article in Newsletter N°21).

First Phase of SPARC

The first Implementation Plan of SPARC was published in 1998 as a WCRP report. It emphasized three of the foci identified in WCRP 93, taking into consideration the evolution of the field in these first years.

• Stratospheric indicators of climate change:

- Detection of stratospheric temperature trends;
- Detection of trends in the vertical distribution of ozone;
- Compilation of a water vapour climatology and detection of long-term changes;
- Stratospheric aerosol climatology and trend;
- Detection of trends in the dynamical activity in the stratosphere.

All but the last one led to SPARC Reports and all led to numerous publications. The paper "Stratospheric temperature trends: observations and model simulations" was awarded the WMO Norbert Gerbier-MUMM Award 2003 and an update of the Temperature Assessment is planned as SPARC Report N°4; the Assessment on Ozone Vertical Profile was published as SPARC Report N°1 in 1998 and was used in WMO/UNEP Ozone Assessment 2002, Chapter 4 of the publication “Global Ozone: past and future”. The Water Vapour Assessment was published as SPARC Report N°2 in 2000. The Aerosol Assessment will be published in 2004 as SPARC Report N°5.

• Stratospheric processes and their relation to climate:

- Stratosphere-troposphere exchange and dynamics and transport in the lower stratosphere and upper troposphere;
- The QBO and its possible role in coupling the stratosphere and troposphere;
- Gravity wave processes and the parametrisation of the effects of unresolved internal gravity waves in global numerical atmospheric models;
- Chemistry and microphysics in the lower stratosphere and upper troposphere.

These issues have been the subjects of several important workshops, (some of them supported by NATO), which led to a few seminal papers that have changed the perception of the dynamical coupling between the two regions (e.g.: Holton et al., Rev Geophys, 1995). This thematic is getting even more emphasis now with the evidence of the Arctic Oscillation (AO) and the presence of Annular Modes connected with the surface. The last issue is getting now more developed in a joint SPARC-IGAC initiative.

• Modelling stratospheric processes and trends and their effects on climate:

- The GCM-Reality Intercomparison Project for SPARC: GRIPS and its successive levels. The results of the activities under GRIPS Level 1 (intercomparisons of models) and Level 2 (impacts of different parameterisation schemes) have already been the subjects of publications in BAMS and JGR in 2000 and JAS in 2002. Level 3 tasks study mechanisms by which various forcing factors control the atmospheric circulation and how they are represented in models and they should be ready in due time for the next WMO-UNEP and IPCC assessments.
- The compilation of a stratospheric reference climatology against which model results can be compared using global satellite data. The output was published as a SPARC Report N°3, 2003).
- The current best estimates of stratospheric parameters, which play a role in climate forcing. Adequate data were provided to IPCC. A recommended set of key indices is being prepared.

The WCRP has also asked the SPARC project to help define the solar forcing to be used in climate models, an activity to be carried out jointly with the SCOSTEP.

It is satisfactory to see that most of the activities decided a decade ago have led to results and that the original goals have been achieved, leaving the place for a new series of initiatives. However, the memory of SPARC past activity should be kept in the SPARC archives. They will be available on the web site and the web version of this SPARC history will direct the reader to the main information which he/she may wish to consult: Implementation Plan; reports of SSGs and working groups, organisation of SPARC Workshops, or related meetings; SPARC general assemblies; SPARC reports and related publications.

The Transition between the two Phases

In those last two years, SPARC has been going through a transition period between its first phase (under the leadership of M. Geller and myself) with the scientific initiatives described above, and a new phase, both due to the change of leadership (A. O’Neill since 2001 and A. Ravishankara since 2003) and the evolution of the projects as scientific priorities are changing. The new initiatives will be described by the SPARC Co-Chairs in the following paper . Other changes going to take place in 2004 are those of Director and site of the SPARC Office, which had been in Verrières-le-Buisson (France) under my leadership since January 1993, and is going to be transferred to the University of Toronto under the leadership of N. Mc Farlane. The new Office will be operational after the SPARC General Assembly in September 2004. We are very happy that Canada has offered to support the new Office. I would like to take this opportunity to thank the French agencies, CNRS/INSU and CNES, for supporting the operation of the Office in France for the last 12 years, as well as Météo-France for publishing the SPARC Newsletter. They should find here not only the expression of my thanks but also of the whole community. Many thanks are also due to NASA whose constant support led to the creation of the SPARC Data Center in Stony Brook, which has been very instrumental in the success of SPARC. Obviously none of the SPARC achievements will have been possible without the continuous support and encouragements of WCRP.