7.4

The Stratospheric response to doubled CO₂ in two chemistry-climate models

Margaret M. Hurwitz, University of Cambridge, Cambridge, United Kingdom; and P. Braesicke, O. Morgenstern, and J. A. Pyle

This study examines the impact of doubling CO₂ on stratospheric dynamics and ozone in two chemistry-climate models. Previous work by these authors, using a climate model with parameterized stratospheric ozone chemistry, found a dependence of northern hemisphere (NH) polar vortex strength on background CO₂ concentration; the polar vortex showed a weakening due to O₃ depletion in present-day conditions, but a strengthening in a double-CO₂ atmosphere. This work is compared with results from the UK Chemistry and Aerosol model (UKCA), a new chemistry-climate model with interactive stratospheric chemistry. Integrating UKCA at both present-day and doubled CO₂ concentrations, small ensembles are constructed by imposing small changes on the initial CO₂ concentrations for each of the ensemble members. The ensemble mean changes in polar vortex strength and ozone concentrations during mid- and late winter, in both hemispheres, are assessed.

  Recorded presentation

Session 7, The Past and Future of Middle Atmosphere Modeling: A Session in Honor of Byron A. Boville
Thursday, 23 August 2007, 1:30 PM-3:00 PM, Multnomah

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