The theory of parallel climate realizations as a new framework for teleconnection analysis

Mátyás Herein,János Márfy,Gábor Drótos,Tímea Haszpra,Tamás Tél

doi:10.1038/srep44529

Mátyás Herein, János Márfy + Show 3 more

Open Access

https://doi.org/10.1038/srep44529

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Abstract

Teleconnections are striking features of the Earth climate system which appear as statistically correlated climate-related patterns between remote geographical regions of the globe. In a changing climate, however, the strength of teleconnections might change, and an appropriate characterization of these correlations and their change (more appropriate than detrending the time series) is lacking in the literature. Here we present a novel approach, based on the theory of snapshot attractors, corresponding in our context to studying parallel climate realizations. Imagining an ensemble of parallel Earth systems, instead of the single one observed (i.e., the real Earth), the ensemble, after some time, characterizes the appropriate probabilities of all options permitted by the climate dynamics, reflecting the internal variability of the climate. We claim that the relevant quantities for characterizing teleconnections in a changing climate are correlation coefficients taken over the temporally evolving ensemble in any time instant. As a particular example, we consider the teleconnections of the North Atlantic Oscillation (NAO). In a numerical climate model, we demonstrate that this approach provides the only statistically correct characterization, in contrast to commonly used temporal correlations evaluated along single detrended time series. The teleconnections of the NAO are found to survive the climate change, but their strength might be time-dependent.

Highlights

T τ are included: detrending has been performed by subtracting a moving average from the original signals, where the moving average is calculated over a time window of length τ = 101 yr
We emphasize that this way we define a climate for each time instant. Note that these considerations imply that any statistics is obtained correctly only if it is evaluated with respect to the plethora of the parallel climate realizations, and this is why we consider any results deviating from those obtained by the snapshot approach inappropriate
When dealing with climate changes induced by shifting parameters, the probability distribution and the ensemble statistics unavoidably change in time[7]

Summary

Introduction

We emphasize that this way we define a climate for each time instant Note that these considerations imply that any statistics is obtained correctly only if it is evaluated with respect to the plethora of the parallel climate realizations, and this is why we consider any results deviating from those obtained by the snapshot approach inappropriate. A basic feature of the approach of parallel climate realizations is the capability of a clear separation of externally induced trends from internal fluctuations (appearing in any individual climate realization). The former are obtained as ensemble averages. The statistics of the internal fluctuations should be investigated in the ensemble framework proposed here

Methods

Conclusion