Gauss, M.¹, G. Myhre¹, G. Pitari², M.J. Prather³, I.S.A. Isaksen¹, T.K. Berntsen¹, G.P. Brasseur⁴, F.J. Dentener⁵, R.G. Derwent⁶, D.A. Hauglustaine⁷, L.W. Horowitz⁸, D.J. Jacob⁹, M. Johnson¹⁰, K.S. Law¹⁰, L.J. Mickley⁹, J.-F. Müller¹¹, P.-H. Plantevin¹⁰, J. A. Pyle¹⁰, H.L. Rogers¹⁰, D.S. Stevenson¹², J.K. Sundet¹¹, M. van Weele¹³, and O. Wild¹⁴

1. Department of Geophysics, University of Oslo, Norway.
2. Dipartimento di Fisica, Università de LAquila, Coppito, LAquila, Italy.
3. Earth System Science Department, University of California at Irvine, USA.
4. Max-Planck-Institut für Meteorologie, Hamburg, Germany.
5. Joint Research Centre, Climate Change Unit, Ispra, Italy.
6. UK Met Office, Climate Research Division, Berks, UK.
7. Institut Pierre Simon Laplace (IPSL), Gif-sur-Yvette, France.
8. GFDL/NOAA, Princeton University, USA.
9. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA.
10. Cambridge University, Chemistry Department, Cambridge, UK.
11. IASB, Brussels, Belgium.
12. Institute for Meteorology, University of Edinburgh, Edinburgh, UK.
13. Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands.
14. Frontier Research System for Global Change (FRSGC), Yokohama, Japan.

Radiative forcing due to changes in ozone is expected for the 21st century. OxComp, a comprehensive modeling study conducted for the IPCC Third Assessment Report (IPCC-TAR), estimated tropospheric changes in ozone and other oxidants during the 21st century based on the SRES A2p emission scenario. In this study we analyze the results of eleven chemical transport models that participated in OxComp and use them as input for detailed radiative forcing calculations. We also address future ozone recovery in the lower stratosphere and its impact on radiative forcing by applying two models that calculate both tropospheric and stratospheric changes. The results of OxComp suggest an increase in global-mean tropospheric ozone between 11.4 to 20.5 DU for the 21st century, representing the model uncertainty range for the A2p scenario. As the A2p scenario constitutes the worst case proposed in IPCC-TAR we consider these results as an upper estimate. The radiative transfer model yields a positive radiative forcing ranging from 0.40 to 0.78 Wm-2 on a global and annual average. The lower stratosphere contributes an additional 7.5 to 9.3 DU to the calculated increase in the ozone column, increasing radiative forcing by 0.15 to 0.17 Wm-2. The modeled radiative forcing depends on the height distribution and geographical pattern of predicted ozone changes and shows a distinct seasonal variation. Despite the large variations between the eleven participating models, the calculated range for normalized radiative forcing is within 25%, indicating the ability to scale radiative forcing to global-mean ozone column change.

J. Geophys. Res., 108(D2), 4292, doi:10.1029/2002JD002624, 2003 (PDF, 1.4 Mb)

(Submitted: 6 June 2002; Revised: 6 November 2002; Accepted: 7 March 2003; Published 13 May 2003)