  We revisit the Parikh-Wilczek tunneling through the de Sitter horizon and
obtain the tunneling rate in Schwarzschild-de Sitter space, which is
non-thermal and closely related to the change of entropy. We discuss the
thermodynamics of Schwarzschild-de Sitter space and show existence of
correlation which ensured the conservation of the total entropy in the
transition process of Schwarzschild-de Sitter space to de Sitter space. The
correlation and the conserved entropy enlighten a way to explain the entropy in
empty de Sitter space.
