It's cold in northern Europe, and the temperature is low. So northern Europeans have bigger noses. The larger nasal cavity can fully buffer and heat the inhaled air before it enters the trachea and lungs to prevent cold air from being directly inhaled into the lungs. In the temperate zone where we live, the climate is not as cold as in northern Europe, so the nasal cavity is smaller than in northern Europe, while the nasal cavity in Africa is smaller than ours.