SLIDE 1 The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
The Ozone Hole and Southern Hemisphere Climate Change
Julie Arblaster
Climate Change Science Team, Bureau of Meteorology Climate Change Prediction group, NCAR www.cawcr.gov.au
SLIDE 2 The Ozone Hole and climate change
NASA
Ozone depletion over
Antarctica of more than 50% compared to 1980 levels Predominantly in spring months, impact on surface climate in summer Recovery of the ozone hole projected by mid-late 21st Century Stratospheric ozone has
global surface temperatures
SLIDE 3
Ozone depletion and Southern Hemisphere atmospheric circulation
Son et al 2010
Depletion => cooling in Antarctic stratosphere => changes in atmospheric circulation and rainfall
DRY WET
recent research suggests jet has moved poleward by ~2 latitude since 1979
SLIDE 4
Ozone depletion and Southern Hemisphere atmospheric circulation
Southern Annular Mode (SAM) index measures strength & position of winds
SAM index
=> Ozone impacts SAM & surface climate predominantly in summer => Recent trend in the SAM due primarily to ozone depletion
Thompson et al. Nature Geosciences, 2011
SLIDE 5
Impacts on surface climate
Impacts of increasing summertime SAM (~ozone depletion)
implications for Antarctic sea-ice, ice sheets and
carbon uptake by the Southern Ocean
Thompson et al. Nature Geosciences, 2011
surface temperature & wind sea surface temperature & wind
SLIDE 6
Impacts on summer surface climate
Impacts of increasing summertime Southern Annular Mode (~ozone depletion) Warm over New Zealand, dry in west, wet in east Wet and cool over southern Australia
Thompson et al. Nature Geosciences, 2011
temperature rainfall rainfall
SLIDE 7 Kang et al., Science, 2011
Recent studies show these impacts can be captured by climate models
Climate model experiments
observed summer rainfall change from 1979-2000 climate model summer rainfall change driven by
SLIDE 8
What of the future?
Son et al 2010
<= past future =>
SLIDE 9
Future changes in the Southern Hemisphere GHGs
Son et al 2010
SLIDE 10
Ozone depletion and atmospheric circulation
Thompson et al. Nature Geosciences, 2011 SAM index SAM index
Ozone depletion
and greenhouse gases act together to drive past changes
Ozone recovery
and greenhouse gases drive opposite changes
Southern Annular Mode (SAM) index measures strength & position of winds
SLIDE 11
Meehl et al, J Climate, 2012 and Cionni et al 2011 New opportunities to assess the role of ozone versus greenhouse gases on the SH circulation in lead up to IPCC 5th Assessment Report: – all models include ozone recovery into the future – a number of chemistry-climate models participating – a number of high-top models participating
Stratospheric ozone depletion and recovery included in all participating models
Climate modelling intercomparison project
SLIDE 12 Future climate change scenarios
- a poleward shift in the SH
extratropical circulation (westerly jet, SAM) is one of the most robust responses to global warming
- ozone recovery will offset
this shift in austral summer to some extent
- which forcing dominates in
future climate change scenarios? => low-emissions scenario RCP2.6: ozone recovery wins and SH winds shift equatorward => high-emissions scenario RCP8.5: GHGs wins and SH winds poleward Meehl et al. J Climate 2012
SLIDE 13 south pole equator height tropopause
Many recent papers on understanding impacts of stratospheric ozone in recent and future trends
- ties to changes in Tropics eg. Hadley Cell and subtropics
- much work on proposed mechanisms
- potential impacts on extremes
Conclusions
The ozone hole has driven much of the observed shift in Southern Hemisphere mid- latitude winds during summer with broad impacts on surface climate Ozone recovery will offset the response to climate change to some extent
?
SLIDE 14 The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
Julie Arblaster Climate Change Science Team, CAWCR Climate Change Prediction group, NCAR Email: j.arblaster@bom.gov.au
Thank you
www.cawcr.gov.au
