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

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.

The Max Planck Institute Grand Ensemble: Enabling the Exploration of Climate System Variability

“…In a large ensemble, ensemble members with a stronger AMOC due to internal variability are likely to show increased surface warming, compared to ensemble members with a weaker AMOC (Maroon et al, ). By utilizing the ensemble dimension (similar to Herein et al, ; Maher et al, ) and computing the standard deviation of any given quantity across the ensemble, we can assess whether projected changes in AMOC variability are time‐dependent.…”

Predicting Climate Change through Response Operators in a Coupled General Circulation Model

“…We apply to the system an additional forcing to the right-hand side of the equations of motion as Ψ (x , t) = X (x )f (t), characterized by a pattern in the phase space X and a time modulation f . Response theory gives a way to compute the response of the expectation value Φ f (t) of the observable, where · indicates the expectation value over an ensemble of independent realizations of the system -in a deterministic dynamical system, a sampling starting from many different initial conditions [24,25].…”

On the time evolution of ENSO and its teleconnections in an ensemble view – a new perspective

“…However, a correct application of temporal statistics requires stationarity, as argued in Drótos et al (2015Drótos et al ( , 2016, which does not hold in a changing climate. The non-stationarity of the climate system naturally appears in the simulations generated for climate projections by general circulation models, and it is especially important in the analysis of teleconnections (Herein et al, 2016(Herein et al, , 2017Roy et al, 2019;Chung et al, 2019).…”

“…Furthermore, starting a sufficiently large ensemble of climate simulations with slightly different initial conditions is proved to correctly cover the distribution of the possible climate states of the snapshot attractor after the transient time at any time instant, therefore, from that time on the ensemble can be used to characterize the potential states at each time instant (Drótos et al, 2015;Herein et al, 2016;Drótos et al, 2017). This ensemble can be also called parallel climate realizations (Herein et al, 2017;Tél et al, 2019). We note that it is remarkable that Leith (1978) came up with a similar idea as early as in 1978, however, Leith's work has not spread widely in the climate community.…”