Long-term changes in the middle atmosphere due to anthropogenic greenhouse gas emissions are examined in relation to the effect of the equatorial Quasibiennal Oscillation (QBO) on the northern winter circulation. The examinations are based on the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations 1979-2100 of the Earth-System-Model MPI-ESM that generates the QBO internally. A remarkable result is that the trends in temperature, zonal wind and residual circulation are much stronger during the westerly (QBO-West) than the easterly (QBO-East) phase of the QBO (factor 2-4). An in-depth-analysis based on recent formulations of the three-dimensional (3D) residual circulation, which represents the 3D Brewer-Dobson circulation (BDC), shows that this trend behavior is related to both the radiative cooling of the middle atmosphere and the changes in the 3D BDC and associated dynamical heating rates, where both affect the strength and position of the polar vortex. In particular, the change in transient eddy fluxes over North America affects the excitation and propagation of planetary Rossby waves due to the Rocky Mountains and, subsequently, the QBO-signal in the stationary planetary wave one (usually pronounced during QBO-East) and wave two (usually pronounced during QBO-West) in temperature, zonal wind and 3D BDC. Effects of changes in the frequency of sudden stratospheric warmings and possible impacts on surface climate are discussed. For verification of the model dynamics, reanalysis data (ERA-Interim), daily-mean wind fields derived from Aura/MLS satellite data and simulations with the general circulation and chemistry model HAMMONIA are also examined.