\label{fig:sam_v_enso}
SAM versus Ni\~{n}o 3.4 for all data times (shown in black) over the period 1979--2014. Dots corresponding to PSA-positive and PSA-negative data times were re-colored red and blue respectively and were arranged in the following order from front to back: blue, red, black (i.e. a blue dot might have red and/or black dots hidden underneath). For clarity, only every seventh data time was plotted. Corresponding histograms and kernel density estimates for the SAM (top panel) and Ni\~{n}o 3.4 (right panel) are shown and have been scaled according to density as opposed to frequency (hence the amplitudes are comparable).