  In this paper, the initial-boundary value problem to the three-dimensional
inhomogeneous, incompressible and heat-conducting Navier-Stokes equations with
temperature-depending viscosity coefficient is considered in a bounded domain.
The viscosity coefficient is degenerate and may vanish in the region of
absolutely zero temperature. Global existence of weak solutions to such a
system is established for the large initial data. The proof is based on a
three-level approximate scheme, the De Giorgi's method and compactness
arguments.
