QGP viscosity from RHIC data -- new perspective from viscous hydrodynamics +URQMD

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 and may work in regions where ideal hydrodynamics fails. In this talk, I will report recent progresses on viscous hydrodynamics and its hybrid approach (viscous hydrodynamics + hadron cascade). Then I will discuss extracting the QGP shear viscosity from RHIC data and show how the theoretical uncertainties are greatly reduced with the new hybrid approach coming out.