Fe/Rayleigh lidar measurements and balloon observations made recently at the geographic South Pole are used to characterize the monthly mean winter temperature profiles from the surface to about 110 km. The measured temperatures during mid-winter in both the stratopause and mesopause regions are 20–30 K colder than current model predictions. These differences are caused by weaker than expected compressional heating associated with subsidence over the polar cap. The measured mesopause temperature responds much more rapidly to changes in sunlight than model predictions, which suggests that IR heating by CO₂ absorption may also be important to the thermal balance in the mesopause region.