Findings since the 2006 Assessment

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Findings since the 2006 Assessment

• SAP co-chairs
• 7th Meeting of the Ozone Research Managers
• Geneva, Switzerland
• May 19, 2008

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Outline

• ClOOCl J-rate revision (Pope et al.)
• EESC adjustments to CFC lifetimes
• Acceleration of the vertical lifting in the
  tropics

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ClOOCl J-rate revision (Pope et al.)
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Pope et al. (2007)

• Ultraviolet Absorption Spectrum of Chlorine
  Peroxide, ClOOCl, Francis D. Pope, Jaron C.
  Hansen, Kyle D. Bayes, Randall R. Friedl, and
  Stanley P. Sander, J. Phys. Chem. A, 111,
  4322-4332, 2007
• ClO ClO M ? ClOOCl M (1a)
• ClOOCl h? ? ClOO Cl (2)
• ClOO M ? Cl O2 M (3)
• 2 Cl O3 ? ClO O2 (4)
• Net 2O3 ? 3O2

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Antarctic Ozone Loss
Oct. 1

• Box model chemistry using JPL (2006) at 80S, 50
  hPa
• Vary J(ClOOCl)
• From sondes we know that O3 is 0 by early Oct.,
  adopting the Pope et al. (2007) rate results in
  less than 50 O3 loss
• Plot from Randy Kawa NASA/GSFC

Polar chemistry workshop for evaluating the new
Pope et al. J rate to be held at Cambridge, UK
(17-19 June, 2008)
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EESC adjustments to CFC lifetimes
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What is EESC?

• Equivalent effective stratospheric chlorine
  (EESC) was developed to relate this halogen
  evolution to tropospheric source gases in a
  simple manner (Daniel et al., 1995)
• EESC represents the levels of Cl Br in the
  stratosphere that can lead to ozone loss.

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EESC (6-year)
6-year old air recovers in 2073
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Emission vs. mixing ratio forcings of
CCMsLifetime problem with CFC-11
CFC-11 Emissions for 1960-2100
Global averaged surface CFC-11 mixing ratio
GEOS CCM Emission CFC-11 lifetime 56 years
2032
2040
WMO A1 Emission CFC-11 lifetime 45 years
Note Assuming total CFC-11 production is the
same, the difference between WMO A1 emission and
model backed-out flux is due to differences in
CFC-11 lifetimes and uncertainty in the remaining
bank estimate. We spread the difference evenly
between 2005-2100 for a modified emission
estimate.
Qing Liang NASA/GSFC
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Summary

• If the new lab measurements of Cl2O2 photolysis
  are correct, then we must make seriously revise
  our current paradigm of polar ozone loss.
• Our future chlorine scenarios are critically
  dependent on lifetimes of ozone depleting
  substances. Revision of the CFC-11 lifetime
  alone will alter our projections of recovery.
• The acceleration of the stratospheric circulation
  is based upon model simulations, not
  observations. A changing circulation will affect
  both ozone and trace gas distributions