Lensing potential power spectra in the base ΛCDM model drawn from the posterior of the lensing-only likelihood (left) and the Planck TT+lowP likelihood (right), coloured by the value of the dark matter density Ω_ch². For fixed CMB power spectra (i.e. the right-hand plot) the lensing power spectrum shape is nearly fixed, but the amplitude increases as the matter density increases across the acoustic-scale degeneracy (the accompanying reduction in A_s is sub-dominant). With lensing reconstruction data, as Ω_ch² varies the lensing spectrum changes shape, with the amplitude around the best-measured L ≈ 150, remaining pinned by the accuracy of the measurement there. A combination of the lensing and Planck TT+lowP data measures the matter density significantly better, with the higher values in the right-hand plot being excluded. Note that the colour scales on the plots are different.