Climate zones

Why the equator is hot and the poles are cold

The Sun does not heat Earth evenly. At the equator (yellow line) its rays hit straight down — hot all year: the tropical zone (reddish). Toward the poles the rays come in at a slant and heat less: the temperate zone (green) — four seasons here, and Uzbekistan is in this zone. Beyond the polar circles (blue) the Sun doesn't rise at all in winter — ice and snow. Animals and plants live according to these zones too.

Climate zones depend on latitude: the tropics (to 23.4°) see the Sun overhead twice a year with little yearly change; the temperate zone (23.4°–66.6°) has clear seasons; the polar zone (above 66.6°) has polar day and night. But altitude (−6 °C per km), distance from the ocean (mild maritime vs harsh continental climate) and currents (the Gulf Stream) matter too — which is why London and the Kazakh steppe differ so much at the same latitude. Biomes — desert, savanna, rainforest, steppe, taiga, tundra — are the result of climate plus rainfall.

Fun facts

• The hottest temperature on Earth was 56.7 °C (Death Valley, USA), the coldest −89.2 °C (Vostok, Antarctica).
• Kilimanjaro sits near the equator, yet its summit has a glacier — altitude "beats" latitude.
• Uzbekistan has a sharply continental climate: up to +45 °C in summer and −20 °C in winter.
• The tropics cover 40% of Earth's surface but are home to half of all people.