Correction to: Nature Climate Change https://doi.org/10.1038/nclimate1352, published 15 January 2012.

In this Letter, the N values presented in Figs. 2a and 2b were mistakenly swapped: this did not affect the statistical outcomes or interpretation of the data. The corrected version of the figure is shown below; the original Letter has not been corrected.

Fig. 2a,b
figure 1

Original and Corrected.