The Latitude Engine

Earth's climate zones begin with latitude: because Earth is round and tilted, sunlight hits the equator more directly than the poles and changes by season. The 23.5-degree axial tilt shapes the seasonal rhythm, while latitude controls how much solar energy each belt receives overall. That is why the equator stays warm year-round and the poles spend winter in darkness.

This uneven heating creates three climate belts. The tropical zone gets the most concentrated sunlight. The temperate zones have moderate conditions with distinct seasons. The polar zones get so little winter sunlight that temperatures can drop below -80 degrees C.