Correction to: Nature Geoscience https://doi.org/10.1038/s41561-018-0235-0, published online 8 October 2018.

In the version of this Article originally published, in Fig. 3a the peak values of M in the northern and southern mid-latitudes in one hemisphere were incorrect. In addition, the two hemispheres were labelled incorrectly. The hemispheres should have been as shown below. This has now been corrected.

Fig. 3
figure 1

Original and corrected.