We are grateful for the insightful comments from Chaim Garfinkel and the two anonymous reviewers. We would also like to thank Brian Hoskins and Lorenzo Polvani for discussions regarding this study. DMM and JA are supported by a grant from the UK Natural Environmental Research Council (NERC) and LJG is funded by the NERC National Centre for Atmospheric Science (NCAS).
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Applying persistence time scales of between 5 and 10 days does not alter the conclusions of this study.
This period was chosen to allow time for anomalies to propagate to the surface following an event onset. Changing the period decreases the magnitude of the signal, but crucially does not alter the significance.
The trend is calculated by applying a least squares linear fit to the time series.