1. Climate change and stratosphere-troposphere coupling: Key questions Eugene Cordero, Nathan Gillett, Michael Sigmond, Shigeo Yoden

2. Brewer-Dobson circulation change: Causes and effects Strengthening BD circulation is a robust result of 21 st century CCM simulations. Strengthening BD circulation is a robust result of 21 st century CCM simulations. Strengthened ascent over tropics, but descending branch may strengthen in mid-lats and not necessarily at poles. Strengthened ascent over tropics, but descending branch may strengthen in mid-lats and not necessarily at poles. Decreases age of air and lifetimes of ODSs. Decreases age of air and lifetimes of ODSs. Decreases tropical ozone and increases polar ozone. Decreases tropical ozone and increases polar ozone. Probably due to increased wave-driving in subtropics (due to increased convection?). Probably due to increased wave-driving in subtropics (due to increased convection?).

3. Models suggest an increase in stratospheric tropical upwelling (Brewer-Dobson circulation) in future climates Butchart et al., 2006 ~2% / decade increase

4. Annular mode changes: Causes and impacts Positive trend in SAM associated with ozone depletion (above lowermost stratosphere). Positive trend in SAM associated with ozone depletion (above lowermost stratosphere). Relative contributions of radiation and dynamics to tropospheric temperature trends remain controverisal. Relative contributions of radiation and dynamics to tropospheric temperature trends remain controverisal. Ozone depletion associated with a delay in wave driving in SH stratosphere associated with final warming. Ozone depletion associated with a delay in wave driving in SH stratosphere associated with final warming. Zonal asymmetries in ozone may be important. Zonal asymmetries in ozone may be important. Future effects: Ozone recovery associated with weakening SH vortex in spring, and possible positive SAM trend. Future effects: Ozone recovery associated with weakening SH vortex in spring, and possible positive SAM trend.

5. Zonal mean response to zonal asymmetry in ozone in October Temperature (°C) Geopotential Height (m) Large zonal mean stratospheric temperature response indicative of a weakened Brewer-Dobson circulation. No significant zonal mean temperature response in troposphere, but significant local surface cooling below stratospheric cooling over Ross Sea.

6. Tropopause changes: Causes Robust upward trend in tropopause, decrease in tropopause temperature. Robust upward trend in tropopause, decrease in tropopause temperature. Appears to be associated mainly with stratospheric temperature changes. Appears to be associated mainly with stratospheric temperature changes. Widening of tropical belt raises subtropical tropopause. Widening of tropical belt raises subtropical tropopause.

7. Source: Diane Seidel

8. Simulating coupled stratosphere-troposphere climate change: What do we need in models? How well do we need to predict stratospheric changes in order to simulate tropospheric changes? How well do we need to predict stratospheric changes in order to simulate tropospheric changes? Low top vs high top comparisons: Very important to keep other factors the same, such as gravity wave parameterisation. Low top vs high top comparisons: Very important to keep other factors the same, such as gravity wave parameterisation. Large differences in strat-trop coupling due to raising model lid above ~10 hPa have not been demonstrated here. Large differences in strat-trop coupling due to raising model lid above ~10 hPa have not been demonstrated here. What are the limitations imposed by prescribed SST? What are the limitations imposed by prescribed SST? Do we need coupled chemistry? Do we need coupled chemistry? How do we weight model predictions? How do we weight model predictions?

9. HIGH LOW AO+ LOWERED LOW-G ∆ SLP = SLP 2xCO2 - SLP control AO+ (0.001 hPa top)(1 hPa top) (10 hPa top) AO+