Nature 419, 224–232 (2002); doi:10.1038/nature01092

We thank P. Good for pointing out that the location of the transient runs (green diamonds) in Fig. 2 of this Insight is inconsistent with the text. With Fs positive downwards and κ positive, the sign of the third term in equation (2) (the hypothesized adjustment for disequilibrium) should be changed, giving:

The analysis and discussion are not affected.