Abstract: Qauasi-geostrophic equation (QG) in 2D is widely considered as a 2D model of a 3D Navier-Stokes equation. Till recently it demonstrated in 2D many obstacles typical for 3D Navier-Stokes. It was known that local regularity holds and the global regularity holds under the extra assumption of small initial data. This is with critical dissipation, and this was done by P. Constantin, D. Cordoba, A. Cordoba, J. Wu. With subcritical dissiapation it was considered by several authors including P. Costantin, D. Cordoba, J. Wu, and with subcritical dissipation global regularity was proved for all initial data. So the question was left: what happens with critical dissipation and non-small initial data? The answer obtained in the joint work of A. Kiselev, F. Nazarov and myself says that global regularity is still valid. In fluid dynamics QG represents the model of strongly rotated fluid. So there is now a rigorous mathematical proof of global regularity in this physically meaningful problem.