Articles | Volume 13, issue 5
https://doi.org/10.5194/acp-13-2563-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/acp-13-2563-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article |
|
05 Mar 2013
Analysis of present day and future OH and methane lifetime in the ACCMIP simulations
A. Voulgarakis, V. Naik, J.-F. Lamarque, D. T. Shindell, P. J. Young, M. J. Prather, O. Wild, R. D. Field, D. Bergmann, P. Cameron-Smith, I. Cionni, W. J. Collins, S. B. Dalsøren, R. M. Doherty, V. Eyring, G. Faluvegi, G. A. Folberth, L. W. Horowitz, B. Josse, I. A. MacKenzie, T. Nagashima, D. A. Plummer, M. Righi, S. T. Rumbold, D. S. Stevenson, S. A. Strode, K. Sudo, S. Szopa, and G. Zeng
NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
Department of Physics, Imperial College, London, UK
UCAR/NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
National Center for Atmospheric Research (NCAR), Boulder, CO, USA
NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
NOAA Earth System Research Laboratory, Boulder, CO, USA
Lancaster Environment Centre, Lancaster University, Lancaster, UK
University of California at Irvine, CA, USA
Lancaster Environment Centre, Lancaster University, Lancaster, UK
NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
Department of Applied Physics and Applied Mathematics, Columbia University, USA
Lawrence Livermore National Laboratory, CA, USA
Lawrence Livermore National Laboratory, CA, USA
Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile (ENEA), Bologna, Italy
Met Office Hadley Centre, Exeter, UK
Department of Meteorology, University of Reading, UK
CICERO, Center for International Climate and Environmental Research Oslo, Oslo, Norway
University of Edinburgh, Edinburgh, UK
Department of Physics, Imperial College, London, UK
NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
Met Office Hadley Centre, Exeter, UK
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
GAME/CNRM, Météo-France, CNRS – Centre National de Recherches Météorologiques, Toulouse, France
University of Edinburgh, Edinburgh, UK
National Institute for Environmental Studies, Tsukuba-shi, Ibaraki, Japan
Environment Canada, Victoria, BC, Canada
Deutsches Zentrum für Luft- und Raumfahrt (DLR), Germany
Met Office Hadley Centre, Exeter, UK
University of Edinburgh, Edinburgh, UK
NASA Goddard Space Flight Center and Universities Space Research Association, Greenbelt, MD, USA
National Institute for Environmental Studies, Tsukuba-shi, Ibaraki, Japan
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/CEA/CNRS/UVSQ/IPSL, France
National Institute of Water and Atmospheric Research, Lauder, New Zealand
Abstract. Results from simulations performed for the Atmospheric Chemistry and Climate Modeling Intercomparison Project (ACCMIP) are analysed to examine how OH and methane lifetime may change from present day to the future, under different climate and emissions scenarios. Present day (2000) mean tropospheric chemical lifetime derived from the ACCMIP multi-model mean is 9.8 ± 1.6 yr (9.3 ± 0.9 yr when only including selected models), lower than a recent observationally-based estimate, but with a similar range to previous multi-model estimates. Future model projections are based on the four Representative Concentration Pathways (RCPs), and the results also exhibit a large range. Decreases in global methane lifetime of 4.5 ± 9.1% are simulated for the scenario with lowest radiative forcing by 2100 (RCP 2.6), while increases of 8.5 ± 10.4% are simulated for the scenario with highest radiative forcing (RCP 8.5). In this scenario, the key driver of the evolution of OH and methane lifetime is methane itself, since its concentration more than doubles by 2100 and it consumes much of the OH that exists in the troposphere. Stratospheric ozone recovery, which drives tropospheric OH decreases through photolysis modifications, also plays a partial role. In the other scenarios, where methane changes are less drastic, the interplay between various competing drivers leads to smaller and more diverse OH and methane lifetime responses, which are difficult to attribute. For all scenarios, regional OH changes are even more variable, with the most robust feature being the large decreases over the remote oceans in RCP8.5. Through a regression analysis, we suggest that differences in emissions of non-methane volatile organic compounds and in the simulation of photolysis rates may be the main factors causing the differences in simulated present day OH and methane lifetime. Diversity in predicted changes between present day and future OH was found to be associated more strongly with differences in modelled temperature and stratospheric ozone changes. Finally, through perturbation experiments we calculated an OH feedback factor (F) of 1.24 from present day conditions (1.50 from 2100 RCP8.5 conditions) and a climate feedback on methane lifetime of 0.33 ± 0.13 yr K−1, on average. Models that did not include interactive stratospheric ozone effects on photolysis showed a stronger sensitivity to climate, as they did not account for negative effects of climate-driven stratospheric ozone recovery on tropospheric OH, which would have partly offset the overall OH/methane lifetime response to climate change.
How to cite. Voulgarakis, A., Naik, V., Lamarque, J.-F., Shindell, D. T., Young, P. J., Prather, M. J., Wild, O., Field, R. D., Bergmann, D., Cameron-Smith, P., Cionni, I., Collins, W. J., Dalsøren, S. B., Doherty, R. M., Eyring, V., Faluvegi, G., Folberth, G. A., Horowitz, L. W., Josse, B., MacKenzie, I. A., Nagashima, T., Plummer, D. A., Righi, M., Rumbold, S. T., Stevenson, D. S., Strode, S. A., Sudo, K., Szopa, S., and Zeng, G.: Analysis of present day and future OH and methane lifetime in the ACCMIP simulations, Atmos. Chem. Phys., 13, 2563–2587, https://doi.org/10.5194/acp-13-2563-2013, 2013.
Received: 31 Jul 2012 – Discussion started: 05 Sep 2012 – Revised: 01 Feb 2013 – Accepted: 12 Feb 2013 – Published: 05 Mar 2013