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 Liu and Fidel González-Ruoco CRCES-IPRC Workshop on Decadal Climate VariabilityCRCES-IPRC Workshop on Decadal Climate Variability, Kona,

Forced Simulation / simulation Time variable solar forcing and volcanic aerosol load; greenhouse gases Forced Simulation / simulation Time 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 Meteorology and run at German Climate Computing Centre (DKRZ) and computing facilities at FZ Jülich

Simulations Christopherus Columbus: Spin-down Initial conditions: Restart files from control experiment. “Warm conditions” Erik den Røde I: Spin-down Initial conditions: Restart files from control experiment. “Warm conditions” Erik den Røde II: (1990) Spin-down Initial conditions: Restart files from Erik I 1700 AD. “Cold conditions”.

Near surface temperature

vs Reconstruction from historical evidence, from Luterbacher et al. Late Maunder Minimum Model-based reconstuction

Global temperature anomaly

 Galapagos (E-Pacific, 1 o S, 90 o W, Dunbar et al., 1994): 367 years of coral  18 O records from , with annual resolution. The intervals , and were found warmer than “normal”, whereas the intervals , (LMM) and cooler than on average.  18 O increases of about ‰ heavier during LMM than between and is indicative for a cooling of K.  New Caledonia (SW-Pacific, 22 o S, 166 o E, Quinn et al., 1998): 335 years of coral  18 O records from , with seasonal resolution. The records describe a brief interval of modest cooling in the late 17th century, with an annual mean SST about K cooler between than between and  Great Barrier Reef, Abraham Reef (SW-Pacific, 22 o S, 153 o E, Druffel and Griffin, 1993): 323 years of coral  18 O records from , with bi-annual resolution. More positive  18 O values (ca. 0.1‰) during the LMM, are consistent with lower SST’s of about 0.5K Zinke, pers. communication

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

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.

Region Described variance (%) reconstructed Christoph Columbus Erik the Red st EOF of Chinese regional temperature (50 year running means)

Extratropical storminess

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 in the historical experiment H (upper panels) and mean number of storm days (10m wind speed reaching at least 10 Bft, lower panels).

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 in the historical experiment H.

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.

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.

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 ,describing 23% and 10% of the variance respectively. Contour interval is 0.5.

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

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.

Scatter diagrams of annual solar constant, derived from Crowley, and the North Hemisphere annual temperature deviations  from the 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 , blue dots include linearly detrended data from