Letter abstract


Nature Geoscience 2, 28 - 31 (2009)
Published online: 14 December 2008 | doi:10.1038/ngeo388

Subject Categories: Atmospheric science | Climate science

Age of stratospheric air unchanged within uncertainties over the past 30 years

A. Engel1, T. Möbius1, H. Bönisch1, U. Schmidt1, R. Heinz2, I. Levin2, E. Atlas3, S. Aoki4, T. Nakazawa4, S. Sugawara5, F. Moore6, D. Hurst6, J. Elkins6, S. Schauffler7, A. Andrews6 & K. Boering8

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The rising abundances of greenhouse gases in the atmosphere is associated with an increase in radiative forcing that leads to warming of the troposphere, the lower portion of the Earth's atmosphere, and cooling of the stratosphere above1. A secondary effect of increasing levels of greenhouse gases is a possible change in the stratospheric circulation2, 3, which could significantly affect chlorofluorocarbon lifetimes4, ozone levels5, 6 and the climate system more generally7. Model simulations have shown that the mean age of stratospheric air8 is a good indicator of the strength of the residual circulation9, and that this mean age is expected to decrease with rising levels of greenhouse gases in the atmosphere10. Here we use balloon-borne measurements of stratospheric trace gases over the past 30 years to derive the mean age of air from sulphur hexafluoride (SF6) and CO2 mixing ratios. In contrast to the models, these observations do not show a decrease in mean age with time. If models are to make valid predictions of future stratospheric ozone levels, and of the coupling between ozone and climate change, a correct description of stratospheric transport and possible changes in the transport pathways are necessary.

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  1. Institute for Atmospheric and Environmental Sciences, Goethe Universität Frankfurt, 60483 Frankfurt, Germany
  2. Institut für Umweltphysik, Universität Heidelberg, 69120 Heidelberg, Germany
  3. Division of Marine and Atmospheric Chemistry, University of Miami, Miami, Florida 33149, USA
  4. Centre for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
  5. Miyagi University of Education, Sendai 980-0845, Japan
  6. Earth System Research Laboratory, NOAA, Boulder, Colorado 80305, USA
  7. Atmospheric Chemistry Division, NCAR, Boulder, Colorado 80307-3000, USA
  8. Departments of Chemistry and of Earth and Planetary Science, University of California, Berkeley, California 94720-1460, USA

Correspondence to: A. Engel1 e-mail: an.engel@iau.uni-frankfurt.de

Correspondence to: F. Moore6D. Hurst6 Also at Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, USA



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