Correction to: Nature https://doi.org/10.1038/s41586-018-0173-4, published online 13 June 2018.

On page 234 of this Perspective, ‘50% decrease’ has been corrected online to ‘50% increase’ in the sentence “The pH of surface waters south of 60° S decreased by 0.2 between 2017 and 2070, equivalent to a 50% increase in the concentration of hydrogen ions since the pre-industrial period1.”.