Berlin 2012 – wissenschaftliches Programm

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AGjDPG: Arbeitsgruppe junge DPG

AGjDPG 7: Climate - Modelling, joint session with jDPG

AGjDPG 7.5: Hauptvortrag

Donnerstag, 29. März 2012, 12:00–12:30, HFT-FT 131

How variable is our climate? — •Thomas Laepple¹ and Peter Huybers² — ¹Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany — ²Harvard University, USA

Determining the magnitude of natural climate variability is neccessary for predicting the plausible range of future climates. While the instrumental record is too short to determine slow climate variations, the analysis of climate archives of the mid-late Holocene (7000yr BP to modern) provides information about variations on decadal to millenial timescales. In a systematic comparison of paleo-temperature records and general circulation model (GCM) simulations, we show that current models systematically underestimate the variance in regional ocean temperature variability during the mid-late Holocene, with the discrepancy increasing from decadal to millennial timescales to more than an order of magnitude. The possibility that the greater variability results from noise in temperature proxies is rejected after analysis of the covariability between instrumental temperature records and coral, alkenone, and Mg/Ca proxies of temperature. The balance of evidence indicates that internal climate variability is much larger than simulated by GCMs on decadal and longer timescales, though the sensitivity of the climate system and magnitude of external forcing could also be greater at multi-decadal and longer timescales than presently accounted for in GCMs. In either case, these results suggests that model simulations are biased toward showing a too stable climate.