Changes in the CMB TT spectrum and foreground spectra, between the best-fitting AL model and the best-fitting base ΛCDM model to the Planck TT+lowP data. The solid blue line shows the difference between the AL model and ΛCDM while the dashed line has the the same values of the other cosmological parameters, but with AL set to unity, to highlight the changes in the spectrum arising from differences in the other parameters. Also shown are the changes in the best-fitting foreground contributions to the four frequency cross-spectra between the AL model and the ΛCDM model. The data points (with ± 1σ errors) are the differences between the high-ℓ maximum-likelihood frequency-averaged CMB spectrum and the best-fitting ΛCDM model to the Planck TT+lowP data (as in Fig. 1). Note that the changes in the CMB spectrum and the foregrounds should be added when comparing to the residuals in the data points.