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Inter-hemispheric temperature variability over the past Millennium
Raphael Neukom
Climate Impacts, Risks and Adaptation Glaciology & Geomorphodynamics Department of Geography University of Zurich
Jeudi 12/03/2015, 11:00-13:00
Bât. 701, P. 17C, LSCE Orme des Merisiers

Information about multi-decadal to centennial-scale climate variability is crucial to understand the dynamics, drivers, and key properties of the Earth’s climate system. Existing quantifications of climate variability and response to forcings over the last millennium are mostly based on data from the Northern Hemisphere only, due to the hitherto lack of high-resolution paleoclimate records from the Southern Hemisphere. However, the number of available paleoclimate proxy data from the Southern Hemisphere has increased considerably over the recent years, now allowing multi-proxy large-scale reconstructions also for this ocean-dominated part of the world. Here, I present the network of annually resolved Southern Hemisphere climate proxy data from different archives (Tree rings, ice cores, corals, sediments, documentary data, and speleothems). Based on this data, I introduce an annually resolved multi-proxy ensemble reconstruction of Southern Hemisphere mean temperatures over the last 1000 years.

The reconstruction is compared to results from the Northern Hemisphere and an ensemble of climate model simulations. The hemispheric reconstructions reveal no globally coherent warm phases in the pre-industrial period, but a clear common warm phase in the late 20th century. In contrast to a “Medieval Climate Anomaly”, we find evidence for a globally consistent peak “Little Ice Age” between 1594 and 1677. Climate models show a much stronger temperature coherence between the hemispheres, which points towards an underestimation of internal climate system variability by the simulations and limited multi-decadal predictability of the climate system on regional to global scales.

Contact : Amaelle Landais
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