For the first time, estimates of heating and cooling in the upper thermosphere due to dissipating and breaking gravity waves (GWs) of tropospheric origin have been obtained with a comprehensive general circulation model (GCM). A GW parameterization specifically designed for thermospheric heights has been implemented in the CMAT2 GCM covering altitudes from the tropopause to the F ₂ region, and simulations for the June solstice have been performed. They reveal that the net thermal effect of GWs above the turbopause is cooling. The largest (up to −170 K d⁻¹ in a zonally and temporally averaged sense) cooling takes place in the high latitudes of both hemispheres near 210 km. The instantaneous values of heating and cooling rates are highly variable, and reach up to 500 and −3000 K d⁻¹ in the F ₂ region, respectively. Inclusion of the GW thermal effects reduces the simulated model temperatures by up to 200 K over the summer pole and by 100 to 170 K at other latitudes near 210 km.