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New Paper: NAO – The Pacemaker of Major Climate Shifts
Wang, Swanson and Tsonis have a paper in press in Geophysical Research Letters (GRL) entitled: ‘The pacemaker of major climate shifts.’ This expands on the very important but largely ignored Tsonis et al (2007) GRL paper, which demonstrated a new dynamical mechanism for major climate shifts.
The Abstract of the new paper states:
Models and data suggest that the interplay of major climate modes may result in climate shifts [Tsonis et al., 2007]. More specifically it has been shown that when the network of North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), El Nino/Southern Oscillation (ENSO) and North Pacific Index (NPI) synchronizes, an increase in the coupling between these oscillations destroys the synchronous state and leads the climate system to a new state. These shifts are associated with significant changes in global temperature trend and in ENSO variability. Here we probe the details of this network’s dynamics to investigate if a certain oscillation is the culprit in these shifts. From a total of 12 synchronization events observed in three climate simulations and in observations we find that the instigator of these shifts is NAO. Without exception only when NAO’s coupling with the Pacific increases a shift will occur. Our results suggest a dynamical sequence of events in the evolution of climate shifts which is consistent with recent independent empirical and modeling studies.
The paper concludes:
Many studies have in the past dealt with the origin and mechanisms of climate oscillations as well as with the consequences of their interactions. Our study with the help of a novel approach identifies for the first time which may be the most significant of these oscillations. In a dynamical scenario where the major modes of variability in the northern hemisphere are synchronized, an increase in the coupling strength destroys the synchronous state and causes climate to shift to a new state. Here we were able to identify that the major participant in this coupling strength increase is NAO, which we found to be behind all climate shifts observed in observations as well as in three climate simulations. Understanding variability of our extremely complex climate system is far from complete as new and often contradicting views are proposed. In this realm we hope that our results will provide some direction and focus to this perpetual quest for understanding climate variability.