Download Links between Ozone and Climate

Links between ozone and climate
SAP Co-chairs
Ayité-Lô Ajavon (Togo)
Paul Newman (USA)
John Pyle (UK)
A.R. Ravishankara (USA)
9th ORM
Geneva, 14 May 2014
Chapter 4 of the upcoming assessment deals with
“Stratospheric ozone changes and climate”.
Chapters 1 and 5 discuss ODS, their replacements
and consider various climate metrics.
Ozone/climate interactions
• Atmospheric ozone is affected by climate change
Transport and temperature-dependent
chemical processes
• Atmospheric ozone can affect climate
New evidence on how stratospheric ozone
changes influence tropospheric weather and
climate
• Climate role of ozone depleting substances and
their replacements
Atmospheric ozone is affected by climate change
• Increases in CO2 cool the stratosphere
Slows down the rate of gas-phase ozone
destruction  O3 increase
Tendency to increase loss in polar latitudes
• Increase in GHGs changes the stratospheric
circulation
Changed circulation changes stratospheric
ozone distribution.
Enhanced stratosphere to troposphere
transport.
Models project a strengthening of the Brewer-Dobson
circulation under climate change
WMO$UNEP)Ozone)Assessment,)2014:)CHAPTER)2,)REVISED)REVIEW)COPY))
Ozone
change is dependent on GHG scenario
NOT)FOR)DISTRIBUTION
— CCMVal-2 / IGAC-SPARC
— RCP 6.0
— RCP 2.6
— RCP 8.5
— RCP 4.5
From Eyring et al, 2013
NB: N2O and CH4 are
chemically active GHGs
Atmospheric ozone can affect climate
• Ozone is a GHG and also absorbs solar
radiation
Stratospheric ozone loss is dominant drive of
observed cooling in the lower stratosphere
• Stratospheric ozone loss likely the dominant
driver of SH circulation changes in recent
decades and has led to various climate effects
Intensification of the summer westerlies;
changes in the Southern Annular Model;
Hadley Cell expansion; precipitation
changes, etc.
• No clear links to climate trends in NH
Ozone loss a major driver of lower stratospheric temperature trends
Eyring et al, 2013
Observed trends in the SH jet are only reproduced
by models including observed ozone loss
EYRING ET AL.: OZONE AND ASSOCIATED CLIMATE IMPACTS
a)
b)
e)
c)
f)
d)
Figure 12. Long-term mean (thin black contour) and linear trend (color) of zonal mean DJF zonal w
or (a) ERA-Interim over 1979–2005; (b) CMIP5 (all models listed in Table 1 except those noted wi
nd (c, d, e, and f) same as Figure 12b but for the four RCPs over 2006–2050.
Contour
intervals of c
Eyring et
al, 2013
1
1
ological wind are 10 ms starting from 20ms . Trends which are statistically significant at th
ODSs and replacements are GHGs
Radiative forcing from ODS and replacements
Projections show different scenarios
Rigby et al, GRL, 2014
Some conclusions
• Because of the impact of GHGs on the troposphere
and stratosphere, reduction of ODS will not return
the ozone layer exactly to its 1980 value
 need for continued measurements of ozone
vertical profile.
• Increasing GHGs alter transport of ozone and other
species in the stratosphere
 need to measure profiles of atmospheric
tracers, like N2O, SF6, etc.
• Stratosphere projected to cool because of GHGs
 need to measure temperature profiles into the
upper stratosphere