Dissertation Award in Nuclear Physics Talk: QGP viscosity at RHIC and LHC energies

The successes of ideal hydrodynamics in describing RHIC data at lower $p_T$ region led to the well known announcement that ``RHIC Scientists Serve Up Perfect Liquid'' (the Quark Gluon Plasma, QGP). In order to answer ``How perfect is the QGP fluid?,'' one needs to extract the QGP viscosity from experimental data. Viscous hydrodynamics is such a tool that could attack this problem. In this talk, I will report recent progresses on viscous hydrodynamics + hadron cascade hybrid model and discuss the QGP shear viscosity at RHIC and LHC energies.