The role of forcing and internal dynamics in explaining the \xe2\x80\x98\xe2\x80\x98Medieval Climate Anomaly\xe2\x80\x99\xe2\x80\x99

• Main Authors: Goosse, H., Crespin, E., Dubinkina, S. (Svetlana), Loutre, M.-F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer ((Germany) Heidelberg) 2012
• Subjects: Arctic; Global warming
• Online Access: https://ir.cwi.nl/pub/22447

Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950\xe2\x80\x931250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.