Articles | Volume 11, issue 15
Atmos. Chem. Phys., 11, 7533–7545, 2011

Special issue: The Modular Earth Submodel System (MESSy) (ACP/GMD inter-journal...

Atmos. Chem. Phys., 11, 7533–7545, 2011

Research article 01 Aug 2011

Research article | 01 Aug 2011

Projections of UV radiation changes in the 21st century: impact of ozone recovery and cloud effects

A. F. Bais1, K. Tourpali1, A. Kazantzidis2, H. Akiyoshi3, S. Bekki4, P. Braesicke5, M. P. Chipperfield6, M. Dameris7, V. Eyring7, H. Garny7, D. Iachetti8, P. Jöckel7, A. Kubin9, U. Langematz9, E. Mancini8, M. Michou10, O. Morgenstern11, T. Nakamura3, P. A. Newman12, G. Pitari8, D. A. Plummer13, E. Rozanov14,15, T. G. Shepherd16, K. Shibata17, W. Tian6, and Y. Yamashita3 A. F. Bais et al.
  • 1Aristotle University of Thessaloniki, Department of Physics, Thessaloniki, Greece
  • 2University of Patras, Department of Physics, Patras, Greece
  • 3National Institute for Environmental Studies, Tsukuba, Japan
  • 4Service d'Aeronomie, Institut Pierre-Simone Laplace, Paris, France
  • 5University of Cambridge, Department of Chemistry, Cambridge, UK
  • 6Institute for Climate and Atmospheric Science, University of Leeds, Leeds, UK
  • 7Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 8Università L'Aquila, Dipartimento di Fisica, L'Aquila, Italy
  • 9Freie Universität Berlin, Institut für Meteorologie, Berlin, Germany
  • 10GAME/CNRM (Météo-France, CNRS), Toulouse, France
  • 11National Institute of Water and Atmospheric Research, Lauder, New Zealand
  • 12NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 13Environment Canada, Victoria, BC, Canada
  • 14Physical-Meteorological Observatory Davos/World Rad. Center, Davos, Switzerland
  • 15Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland
  • 16Department of Physics, University of Toronto, Toronto, Canada
  • 17Meteorological Research Institute, Tsukuba, Japan

Abstract. Monthly averaged surface erythemal solar irradiance (UV-Ery) for local noon from 1960 to 2100 has been derived using radiative transfer calculations and projections of ozone, temperature and cloud change from 14 chemistry climate models (CCM), as part of the CCMVal-2 activity of SPARC. Our calculations show the influence of ozone depletion and recovery on erythemal irradiance. In addition, we investigate UV-Ery changes caused by climate change due to increasing greenhouse gas concentrations. The latter include effects of both stratospheric ozone and cloud changes. The derived estimates provide a global picture of the likely changes in erythemal irradiance during the 21st century. Uncertainties arise from the assumed scenarios, different parameterizations – particularly of cloud effects on UV-Ery – and the spread in the CCM projections. The calculations suggest that relative to 1980, annually mean UV-Ery in the 2090s will be on average ~12 % lower at high latitudes in both hemispheres, ~3 % lower at mid latitudes, and marginally higher (~1 %) in the tropics. The largest reduction (~16 %) is projected for Antarctica in October. Cloud effects are responsible for 2–3 % of the reduction in UV-Ery at high latitudes, but they slightly moderate it at mid-latitudes (~1 %). The year of return of erythemal irradiance to values of certain milestones (1965 and 1980) depends largely on the return of column ozone to the corresponding levels and is associated with large uncertainties mainly due to the spread of the model projections. The inclusion of cloud effects in the calculations has only a small effect of the return years. At mid and high latitudes, changes in clouds and stratospheric ozone transport by global circulation changes due to greenhouse gases will sustain the erythemal irradiance at levels below those in 1965, despite the removal of ozone depleting substances. At northern high latitudes (60°–90°), the projected decreases in cloud transmittance towards the end of the 21st century will reduce the yearly average surface erythemal irradiance by ~5 % with respect to the 1960s.

Final-revised paper