How is the evolution of stratospheric ozone affected by climate change, and how strong is the feedback? (SHARP-OFC)
Final Report Abstract
During the second phase of the SHARP-OCF project advanced aspects of the ozone-climate feedback mechanisms were investigated using a combination of observational and climate model data. Observational data were based upon satellite and balloon-borne data of key trace gas species that allowed us to study past changes in ozone and ozone depleting substances (ODSs), mainly bromine containing species. The state-of-the-art ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistryclimate model (CCM) was employed to interpret past changes as well as to predict ozone evolution under different future climate scenarios up to the end of this century. Height resolved satellite ozone time series from SCIAMACHY and MIPAS (and in combination with other satellite data) show clear evidence that ozone is increasing at a rate of about +2% per decade in the upper stratosphere (~40 km altitude) which is expected as a result of the Montreal Protocol and Amendments phasing out ODSs. In the lower stratosphere where most ozone is located ozone recovery is not yet significant as ozone changes are dominated by the rather large year-to-year variability. In some regions like in the tropics, ozone shows a continued decline at about 30 km and just above the tropopause, which is a result of a combination of changes in tropical upwelling, a possible climate response, and related changes in ozone chemistry in the middle stratosphere. Using EMAC CCM runs with a single forcing (e.g., greenhouse gas (GHG) or ODS changes only) and comparing to model runs with combined forcing (ODS and GHG), individual drivers of past ozone changes were identified. Before 2000 decreases in stratospheric ozone were mainly caused by increases in ODSs, while both changes in GHG concentrations and reduction in ODSs will increase ozone throughout the stratosphere in the future. An exception is the lowermost stratosphere in the tropics where the enhanced entrainment of ozone poor air from the upper troposphere due to a stronger Brewer-Dobson circulation (increased upwelling) will overcompensate the enhanced chemical ozone production related to GHG increases. Depending on future GHG scenarios assumed, total stratospheric ozone will likely decrease in the tropics in the second half of this century. While there is a potential of sporadic strong ozone loss in Arctic spring, like observed in March 2011, in the near future, there is no more evidence for such events in EMAC CCM projections of the second half of this century. Apart from chlorine containing substances, other halogens play an important role in stratospheric ozone depletion. From a set of recent different aircraft- and balloon-borne measurements of BrO and IO, photochemical information on inorganic bromine and iodine was inferred, and their recent trend was established and updated. Transport pathways into the stratosphere were investigated from these observations in combination with chemistry-transport model calculations. In particular, brominated veryshort-lived substances (VSLS) have a non-negligible contribution to the bromine budget and model studies show that they significantly contributed to total ozone trends in the past. CCM studies showed that stratospheric entry amounts of brominated VSLS will possibly decrease in the future. The results from SHARP II contributed significantly to the previous WMO/UNEP Scientific Assessment of Ozone Depletion: 2014 and provide significant contributions to the upcoming ozone assessment
Publications
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(2013), Contribution of very short-lived substances to stratospheric bromine loading: uncertainties and constraints, Atmos. Chem. Phys., 13, 1203-1219
Aschmann, J., and B.-M. Sinnhuber
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(2014), Chemical contribution to future tropical ozone change in the lower stratosphere, Atmos. Chem. Phys., 14, 2959–2971
Meul, S., U. Langematz, S. Oberländer, H. Garny, and P. Jöckel
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(2014), On the hiatus in the acceleration of tropical upwelling since the beginning of the 21st century, Atmos. Chem. Phys., 14, 12803-12814
Aschmann, J., Burrows, J. P., Gebhardt, C., Rozanov, A., Hommel, R., Weber, M., and Thompson, A. M.
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(2014), Stratospheric ozone trends and variability as seen by SCIAMACHY during the last decade, Atmos. Chem. Phys., 14, 831-846
Gebhardt, C., Rozanov, A., Hommel, R., Weber, M., Bovensmann, H., Burrows, J. P., Degenstein, D., Froidevaux, L., and Thompson, A. M.
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(2015), Simulating the impact of emissions of brominated very shortlived substances on past stratospheric ozone trends, Geophys. Res. Lett.
Sinnhuber, B.-M. und S. Meul
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Transition operator calculation with the Green's dyadic technique for electromagnetic scattering: a numerical approach using the Dyson equation (2015), Journal Quant. Spectrosc. Ra., 162, 77- 88
Tricoli, U., P. Vochezer, and K. Pfeilsticker
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(2016), Impact of rising greenhouse gas concentrations on future tropical ozone and UV exposure, Geophys. Res. Lett., 43
Meul, S., M. Dameris, U. Langematz, J. Abalichin, A. Kerschbaumer, A. Kubin, and S. Oberländer- Hayn
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(2017), Brominated VSLS and their influence on ozone under a changing climate, Atmos. Chem. Phys., 17, 11313-11329
Falk, S., B.-M. Sinnhuber, G. Krysztofiak, P. Jöckel, P. Graf, and S. Lennartz
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(2017), Detecting recovery of the stratospheric ozone layer, Nature, 549, 211–218
Chipperfield, M. P., Bekki, S., Dhomse, S., Harris, N. R. P., Hassler, B., Hossaini, R., Steinbrecht, W., Thiéblemont, R. and Weber, M.
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(2017), Probing the subtropical lowermost stratosphere and the tropical upper troposphere and tropopause layer for inorganic bromine, Atmos. Chem. Phys., 17, 1161-1186
Werner, B., Stutz, J., Spolaor, M., Scalone, L., Raecke, R., Festa, J., Colosimo, S. F., Cheung, R., Tsai, C., Hossaini, R., Chipperfield, M. P., Taverna, G. S., Feng, W., Elkins, J. W., Fahey, D. W., Gao, R.-S., Hintsa, E. J., Thornberry, T. D., Moore, F. L., Navarro, M. A., Atlas, E., Daube, B. C., Pittman, J., Wofsy, S., and Pfeilsticker, K.
