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Ozone-Circulation Feedback: Its Effects on Climate Model Output

Paper Reviewed
Nowack, P.J., Abraham, N.L., Maycock, A.C., Braesicke, P., Gregory, J.M., Joshi, M.M. Osprey, A. and Pyle, J.A. 2015. A large ozone-circulation feedback and its implications for global warming assessments. Nature Climate Change 5: 41-45.

Nowack et al. (2014) write that "state-of-the-art climate models now include more climate processes simulated at higher spatial resolution than ever," but they state that "some processes, such as atmospheric chemical feedbacks, are still computationally expensive," and they say they are therefore "often ignored in climate simulations," citing the studies of Taylor et al. (2012) and Kravitz et al. (2013).

In further exploring the various ramifications of this neglect, the eight UK researchers used "a comprehensive atmosphere-ocean chemistry-climate model" to find "an increase in global mean surface warming of around 1°C (~20%) after 75 years when ozone is prescribed at pre-industrial levels compared with when it is allowed to evolve self-consistently in response to an abrupt 4 x CO2 forcing." And in light of these facts, they conclude that model- and scenario-consistent representations of ozone are required, in contrast to the procedure that is widely applied in climate change assessments, where "participating models often use simplified treatments of atmospheric composition changes that are consistent with neither the specified greenhouse gas forcing scenario nor the associated atmospheric circulation feedbacks," citing the work of Cionni et al. (2011), Jones et al. (2011) and Eyring et al. (2013).

In further discussing the results of Nowack et al.'s analysis, Stevenson (2015) says their research "shows that the details of how stratospheric ozone is represented in models can have a strong influence on warming projections." And as Previdi and Polvani (2014) have recently found to be the case in this regard, ozone recovery following the phasing out of the use of ozone-depleting substances "will figure prominently in future climate change, with its impacts expected to largely cancel the impacts of increasing greenhouse gases during the next half-century."

Cionni, I., Eyring, V., Lamarque, J.F., Randel, W.J., Stevenson, D.S., Wu, F., Bodeker, G.E., Shepherd, T.G., Shindell, D.T. and Waugh, D.W.2011. Ozone database in support of CMIP5 simulations: Results and corresponding radiative forcing. Atmospheric Chemistry and Physics 11: 11,267-11,292.

Eyring, V., Arblaster, J.M., Cionni, I., Sedlacek, J., Perlwitz, J., Young, P.J., Bekki, S., Bergmann, D., Cameron-Smith, P., Collins, W.J., Faluvegi, G., Gottschaldt, K.-D., Horowitz, L.W., Kinnison, D.E., Lamarque, J.-F., Marsh, D.R., Saint-Martin, D., Shindell, D.T., Sudo, K., Szopa, S. and Watanabe, S. 2013. Long-term ozone changes and associated climate impacts in CMIP5 simulations. Journal of Geophysical Research 118: 5092-5060.

Jones, C.D., Hughes, J.K., Bellouin, N., Hardiman, S.C., Jones, G.S., Knight, J., Liddicoat, S., O'Connor, F.M., Andres, R.J., Bell, C., Boo, K.-O., Bozzo, A., Butchart, N., Cadule, P., Corbin, K.D., Doutriaux-Boucher, M., Friedlingstein, P., Gornall, J., Gray, L., Halloran, P.R., Hurtt, G., Ingram, W.J., Lamarque, J.-F., Law, R.M., Meinshausen, M., Osprey, S., Palin, E.J., Parsons Cini, L., Raddatz, T., Sanderson, M.G., Sellar, A.A., Schurer, A., Vlades, P., Wood, N., Woodward, S., Yoshioka, M. and Zerroukat, M. 2011. The HadGEM2-ES implementation of CMIP5 centennial simulations. Geoscience Model Development 4: 543-570.

Kravitz, B., Robock, A., Forster, P.M., Haywood, J.M., Lawrence, M.G. and Schmidt, H. 2012. An overview of the Geoengineering Model Intercomparison Project (GeoMIP). Journal of Geophysical Research 118: 13,103-13,107.

Previdi, M. and Polvani, L.M. 2014. Climate system response to stratospheric ozone depletion and recovery. Quarterly Journal of the Royal Meteorological Society 140: 2401-2419.

Stevenson, D.S. 2015. Climate's chemical sensitivity. Nature Climate Change 5: 21-22.

Taylor, K.E., Stouffer, R.J. and Meehl, G.A. 2012. An overview of CMIP5 and the experiment design. Bulletin of the American Meteorological Society 93: 485-498.

Posted 20 April 2015