the tSZ amplitude has the statistical power to tightly constrain $\sigma_8$. A significant challenge in modeling the tSZ power spectrum is that it draws power from a wide range of cluster masses and redshifts. Uncertainties about non-gravitational heating effects complicate models of low-mass clusters, while models of high-redshift clusters suffer from limited observational data. Different prescriptions for cluster gas physics in recent models lead to differences in power of up to 50% for the same cosmology [@sehgal10; @shaw10; @battaglia12; @mccarthy14].

The post-reionization kSZ power spectrum is expected to be simpler to model than the tSZ spectrum because it is not weighted by the gas temperature, and thus depends less on non-linear physics in dense halos. The details of cosmic reionization, however, are crucial to modeling the total kSZ power spectrum, and this epoch is not yet well understood. In the standard picture of cosmic reionization, ionized bubbles form around the first stars, galaxies, and quasars. These bubbles eventually overlap and merge, leading to a fully ionized universe. Proper motion of these ionized bubbles generates angular anisotropy through the kSZ effect. The amplitude of this “patchy” kSZ power depends primarily on the duration of reionization, and its shape primarily on the 