Hubble constant difference between CMB lensing and BAO measurements

We apply a tension metric QUDM, the update difference in mean parameters, to understand the source of the difference in the measured Hubble constant H0 inferred with cosmic microwave background (CMB) lensing measurements from the Planck satellite (H0=67.9-1.3+1.1 km/s/Mpc) and from the South Pole Telescope (H0=72.0-2.5+2.1 km/s/Mpc) when both are combined with baryon acoustic oscillation (BAO) measurements with priors on the baryon density (BBN). QUDM isolates the relevant parameter directions for tension or concordance where the two datasets are both informative and aids in the identification of subsets of data that source the observed tension. With QUDM, we uncover that the difference in H0 originates from differences between Planck lensing and BAO+BBN data, at a probability to exceed of 6.6%. Most of this mild disagreement comes from the galaxy BAO measurements parallel to the line of sight in the redshift range 0.2<0.75. The redshift dependence of the parallel BAOs pulls both the matter density ωm and H0 high in ΛCDM, but these parameter anomalies are usually hidden when the BAO measurements are combined with other cosmological datasets with much stronger ωm constraints.