1. CH2018: Multi-member ensemble simulations to explore decadal variability Stefan Broennimann 1,2, Marco Rohrer 1,2, Christoph C. Raible 2,3 1 Institute of Geography, University of Bern, Switzerland 2 Oeschger Centre for Climate Change Research, University of Bern, Switzerland 3 Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland

2. Overview Available Simulations Drought years during 1945 -1952 Decadal variability of European heatwaves Decadal changes of atmospheric blocking Adds 2

3. Simulations Model: ECHAM5.4 Resolution: T63/L31 up to 10hPa 3

4. Simulations Model: ECHAM5.4 Resolution: T63/L31 up to 10hPa Forcing: SST reconstruction (Mann et al. 2008) Solar irradiance (Lean 2000) Volcanic eruptions (Crowley et al. 2008) GHG (as used in Yoshimori et al. 2010) Land use (Pongratz et al. 2008), bug!!! Aerosols (Koch et al. 1999) before 1850 constant 4

5. Simulations Model: ECHAM5.4 Resolution: T63/L31 up to 10hPa Forcing: SST reconstruction (Mann et al. 2008) Solar irradiance (Lean 2000) Volcanic eruptions (Crowley et al. 2008) GHG (as used in Yoshimori et al. 2010) Land use (Pongratz et al. 2008), bug!!! Aerosols (Koch et al. 1999) before 1850 constant Ensemble approach Different initial conditions obtained from a 1600 AD control simulation 30 ensemble members, 28 normally used 5

6. Evaluation 6 Known shortcomings: Land surface: only 9 from 14 types are implemented SST variability too low due to reconstruction method Sea ice constant before 1870

7. Evaluation 7

8. Drought years during 1945 -1952 8 Broennimann (2015, in press) 1952 1950 1949 1947 1945 ObservationEsemble mean ObservationEsemble mean

9. Decadal variability of European heatwaves 9 Broennimann (2015, in press) Reconstructed AMO and simulated area fraction for US and Europe when max. temperature excceeds the 90th percentile (1901-2000) Ensemble meanEnsemble ranges«best» member -0.1 -0.2 0.0 0.1 AMO (C)

10. Decadal changes of atmospheric blocking 10 Winter Blocking Frequency in North Atlantic/Europe (-70 to10E, 40 to 80N; Member 025) Rohrer et al. (xxx)

11. Decadal changes of atmospheric blocking 11 Winter Blocking Frequency: Ensemble mean Rohrer et al. (xxx)

12. Adds Land use bug: additional simulations are available to assess the impact (relevance for extremes such as heat waves) CC400: Cyclone analysis CESM1: 850 -2100 AD cyclone variability 12 Blumer et al (2015, in prep.)