This paper presents a statistical diagnostic to interpret the dynamics of nonlinear variability in models. It consists in applying the Multichannel Singular Spectrum Analysis to the variability of a suitable equation of a dynamical system. This method enables us to evaluate the sensitivity of the oscillatory features of a physical model to tendencies in its mathematical formulation. Hence, responses in amplitude and frequency are determined in the phase space of the model. The example of

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... nual variability of the tropical Pacific climate through the analysis the Sea Surface Temperature equation of a hybrid coupled model is used to illustrate and validate the methodology.