We would like to clarify some points arising from your News report on the debate over data from the European Space Agency's Planck mission (see Nature http://doi.org/q8t; 2013).

The cosmological parameters estimated by the Planck Collaboration are statistically compatible with those estimated by NASA's Wilkinson Microwave Anisotropy Probe (see G. Hinshaw et al. Astrophys J. Suppl. S. 208, 19; 2013). Also, the analysis of the Planck data by David Spergel and colleagues (see preprint at http://arxiv.org/abs/1312.3313; 2013) is actually in close agreement with our own (http://arxiv.org/abs/1303.5076; 2013): the values of their parameters are within one standard deviation of ours.

For example, their value of the Hubble constant is within 0.6 of a standard deviation of ours; the matter density and the amplitude of the fluctuation spectrum differ by about one standard deviation. These differences, which are not evident in our analyses of the Planck data, could be caused by methodological variations between the respective analyses rather than by systematic errors in the Planck data.

We, and Spergel and colleagues, have verified that the small, time-dependent systematic errors that affect a subset of the data at a radio frequency of 217 gigahertz, which we reported on in the revised versions of the Planck papers from 2013, have little impact on the Planck Collaboration's cosmological results.