Hans von Storch, Eduardo Zorita, Irene Fischer-Bruns, Jian Liu and Fidel Gonz ález-Ruoco

1. Variability on time scales of decades up to a century in a AOGCM simulation with realistic time-variable forcing Hans von Storch, Eduardo Zorita, Irene Fischer-Bruns, Jian Liuand Fidel González-Ruoco CRCES-IPRC Workshop on Decadal Climate Variability, Kona, 23-26.2.2004

2. Forced Simulation 1000-1990 / 1550-1990 simulationTime variable solar forcing and volcanic aerosol load; greenhouse gases Climate model used Atmosphere: ECHAM4 horizontal representation T30 ~ 300 km at mid latitudes Ocean: HOPE-G horizontal representation T42 ~ 200 km at mid latitudes increased resolution in the tropics Model provided as community climate model by Model & Data Group at MPI for Meteorologyand run at German Climate Computing Centre (DKRZ)and computing facilities at FZ Jülich

3. Simulations • Christopherus Columbus: 1465-1990Spin-down 1465-1500. Initial conditions: Restart files from control experiment. “Warm conditions” • Erik den Røde I: 900-1990Spin-down 901-1000. Initial conditions: Restart files from control experiment. “Warm conditions” • Erik den Røde II: 900-1210 (1990)Spin-down 901-1000. Initial conditions: Restart files from Erik I 1700 AD. “Cold conditions”.

9. Near surface temperature

11. Reconstruction from historical evidence, from Luterbacher et al. Late Maunder Minimum Model-based reconstuction 1675-1710vs. 1550-1800

12. Global 1675-1710 temperature anomaly

13. ·Galapagos (E-Pacific, 1oS, 90oW, Dunbar et al., 1994): 367 years of coral 18O records from 1587-1953, with annual resolution. The intervals 1660-80, 1710-1800 and 1870-95 were found warmer than “normal”, whereas the intervals 1600-1660, 1680-1700 (LMM) and 1800-25 cooler than on average. 18O increases of about 0.1-0.15‰ heavier during LMM than between 1660-70 and 1705-50 is indicative for a cooling of 0.5-0.75K. ·New Caledonia (SW-Pacific, 22oS, 166oE, Quinn et al., 1998): 335 years of coral 18O records from 1657-1952, with seasonal resolution. The records describe a brief interval of modest cooling in the late 17th century, with an annual mean SST about 0.2-0.3K cooler between 1680-1740 than between 1660-80 and 1740-50 ·Great Barrier Reef, Abraham Reef (SW-Pacific, 22oS, 153oE, Druffel and Griffin, 1993): 323 years of coral 18Orecords from 1635-1957, with bi-annual resolution. More positive 18O values (ca. 0.1‰) during the LMM, are consistent with lower SST’s of about 0.5K Zinke, pers. communication

14. Ice Cores From Greenland and Antarctica North Greenland Stacked isotope record from five North-Greenland ice cores (Schwager, 2000) Reconstruction of solar variability, deduced from 10Be measurements (Crowley, 2000) Antarctica Stacked isotope record from three ice cores from Dronning Maud Land, Antarctica (Graf et al., in press )

15. Comparisons of reconstructed and simulated 5-decade running mean temperature anomaly series for two regions of China. The vertical hatching indicates the uncertainty of the reconstruction.

16. 1st EOF of Chinese regional temperature (50 year running means)

17. Extratropical storminess

18. Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern winter season DJF (left) and in the southern winter season JJA (right) for the pre-industrial period 1551-1850 in the historical experiment H (upper panels) and mean number of storm days (10m wind speed reaching at least 10 Bft, lower panels).

19. Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern winter season DJF (left) and in the southern winter season JJA (right) for the industrially influenced period 1851-1990 in the historical experiment H.

20. Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern winter season DJF (left) and in the southern winter season JJA (right) during the last 300 years of the control run of 1000 years length.

21. Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern winter season DJF (left) and in the southern winter season JJA (right) in the climate change experiment.

22. Leading EOFs of the mean number of gale days in the historical run for the northern (left) and southern (right) winter hemispheres, obtained from anomaly fields relative to the pre-industrial years 1551-1850,describing23% and 10% of the variance respectively. Contour interval is 0.5.

23. Hemispheric mean temperature as well as PC time series describing storminess on winter hemispheres. The time series have been low pass filtered by computing an 11-year running mean and normalized to unit variance and zero mean in the pre-industrial period. Green: storminess in H (until 1990) and in CC (after 1990). Blue: AO-index or AAO index in H and in CC.Red/orange curves: winter near-surface air temperature in H and CC.The bold grey lines indicate 2 standard deviations for the pre-industrial period of H, continuing as thin grey lines

24. Conclusion • Historical runs done. • Realistic sequence of warming and cooling. • Variations larger than in proxy reconstructions, but consistent with a series of data. • Storm variability during historical times unrelated to NH mean temperature. • Parallel increase of storminess and NH temperature in a climate change scenario.

25. Scatter diagrams of annual solar constant, derived from Crowley, and the North Hemisphere annual temperature deviations from the 1948-1990 mean for the NCEP data set,  the Jones et al. instrumental data,  the ECHO-G simulations and  the MBH99 reconstruction. Black dots include data from the period 1600-1900, blue dots include linearly detrended data from 1900-1990.