  The strong dependence of the mass variance parameter, sigma_8, on the adopted
cluster mass-temperature relation is explored. A recently compiled X-ray
cluster catalog and various mass-temperature relations are used to derive the
corresponding values of sigma_8. Calculations of the power spectrum of the CMB
anisotropy induced by the Sunyaev-Zeldovich effect and cluster number counts
are carried out in order to assess the need for a consistent choice of the
mass-temperature scaling and the parameter sigma_8. We find that the
consequences of inconsistent choice of the mass-temperature relation and
sigma_8 could be quite substantial, including a considerable mis-estimation of
the magnitude of the power spectrum and cluster number counts. Our results can
partly explain the large scatter between published estimates of the power
spectrum and number counts. We also show that the range of values of the
power-law index in the scaling C_l ~ sigma_8^[6-7] deduced in previous studies
is likely overestimated; we obtain a more moderate dependence, C_l ~
sigma_8^[4].
