  The peculiar motion of ionized baryons is known to introduce temperature
anisotropies in the CMB by means of the kinetic Sunyaev-Zel'dovich effect
(kSZ). In this work, we present an all sky computation of angular power
spectrum of the temperature anisotropies introduced by kSZ momentum of all
baryons in the Universe during and after reionization. In an attempt to study
the bulk flows of the missing baryons not yet detected, we address separately
the contribution from all baryons in the IGM and those baryons located in
collapsed structures like groups and clusters of galaxies. In the first case,
our approach provides a complete, all sky computation of the kSZ in second
order of cosmological perturbation theory (also known as the Ostriker-Vishniac
effect, OV). Most of the power of OV is generated during reionization, although
it has a non-negligible tail at low redshifts, when the bulk of the kSZ
peculiar momentum of the halo (cluster + group) population arises. If gas
outside halos is comoving with clusters as the theory predicts, then the
signature of the bulk flows of the missing baryons should be recovered by a
cross-correlation analysis of future CMB data sets with kSZ estimates in
clusters of galaxies. For an ACT or SPT type of CMB experiment, all sky kSZ
estimates of all clusters above $2\times 10^{14} h^{-1}M_{\odot}$ should
provide a detection of {\it dark} flows with signal to noise ratio (S/N) of
$\sim 10$, (S/N $\sim 2.5-5$ for 2,000 - 10,000 square degrees). Improving kSZ
estimates with data from Large Scale Structure surveys should enable a deeper
confrontation of the theoretical predictions for bulk flows with observations.
The combination of future CMB and optical data should shed light on the dark
flows of the nearby, so far undetected, diffuse baryons.
