High temperatures at the beginning of December

The first December shows a Global Warming of 11.46 Celsius. It must be remembered that this means that the average temperature for the whole month of December is 11.46 C above average. The temperature will hopefully progressively fall until the end of December, because the planet is entering the winter season.

Exactly why this should be so, is not entirely clear to me, either. I suspect that there is more landmass in the northern half of the Earth than in the South. Or because there are more weather stations in the north to record the temperature.