Uncertainties and assessments of chemistry-climate models of the stratosphere J. Austin1, D. Shindell2, S. R. Beagley3, C. Brühl4, M. Dameris5, E. Manzini6, T. Nagashima7, P. Newman8, S. Pawson8, G. Pitari9, E. Rozanov10, C. Schnadt5, and T. G. Shepherd11 1Meteorological Office, London Rd., Bracknell, Berks., RG12 2SZ, UK 2NASA-Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA 3York University, Canada 4Max Planck Institut für Chemie, Mainz, Germany 5DLR, Oberpfaffenhofen, Weßling, Germany 6Max Planck Institut für Meteorologie, Hamburg, Germany 7Center for Climate System Research, University of Tokyo, Japan 8Goddard Earth Sciences and Technology Center, NASA/Goddard Space Flight Center Code 916, Greenbelt, MD 20771, USA 9Dipartamento di Fisica, Universit`a de L’Aquila, 67010 Coppito, L’Aquila, Italy 10PMOD-WRC/ IAC ETH, Dorfstrasse 33, Davos Dorf CH-7260, Switzerland 11Department of Physics, University of Toronto, Toronto, Ontario, Canada
Abstract. In recent years a number of chemistry-climate models have been developed with
an emphasis on the stratosphere. Such models cover a wide range of time scales of integration and vary considerably in complexity. The results of
specific diagnostics are here analysed to examine the differences amongst individual models and observations, to assess the consistency of model
predictions, with a particular focus on polar ozone. For example, many models
indicate a significant cold bias in high latitudes, the "cold pole problem",
particularly in the southern hemisphere during winter and spring. This is related to wave propagation from the troposphere which can be improved by
improving model horizontal resolution and with the use of non-orographic gravity wave drag. As a result of the widely differing modelled polar
temperatures, different amounts of polar stratospheric clouds are simulated
which in turn result in varying ozone values in the models.
The results are also compared to determine the possible future behaviour of
ozone, with an emphasis on the polar regions and mid-latitudes. All models
predict eventual ozone recovery, but give a range of results concerning its
timing and extent. Differences in the simulation of gravity waves and planetary waves as well as model resolution are likely major sources of
uncertainty for this issue. In the Antarctic, the ozone hole has probably reached almost its deepest although the vertical and horizontal extent of
depletion may increase slightly further over the next few years. According to
the model results, Antarctic ozone recovery could begin any year within the
range 2001 to 2008.
The limited number of models which have been integrated sufficiently far indicate that full recovery of ozone to 1980 levels may not occur in the
Antarctic until about the year 2050. For the Arctic, most models indicate that small ozone losses may continue for a few more years and that recovery
could begin any year within the range 2004 to 2019. The start of ozone recovery in the Arctic is therefore expected to appear later than in the
Further, interannual variability will tend to mask the signal for longer than
in the Antarctic, delaying still further the date at which ozone recovery may
be said to have started. Because of this inherent variability of the system,
the decadal evolution of Arctic ozone will not necessarily be a direct response to external forcing.
Citation: Austin, J., Shindell, D., Beagley, S. R., Brühl, C., Dameris, M., Manzini, E., Nagashima, T., Newman, P., Pawson, S., Pitari, G., Rozanov, E., Schnadt, C., and Shepherd, T. G.: Uncertainties and assessments of chemistry-climate models of the stratosphere, Atmos. Chem. Phys., 3, 1-27, doi:10.5194/acp-3-1-2003, 2003.