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Weather and climate


Morning fog in a tropical rainforestMorning fog in a tropical rainforest Weather varies from day to day around the world. Over a longer period, especially many years, each region has a regular pattern of rain, wind, temperature and other weather features. This long-term pattern of weather is called climate. A region's climate is the result of a number of factors: its latitude, which affects the amount of heat it receives from the Sun; its altitude (in upland areas the air is thinner and cooler); the way that ocean currents and wind patterns carry the Sun’s warmth and rain-laden clouds around the globe.

World climate regions

A map showing the world’s main climate regions A map showing the world’s main climate regions Different regions of the world have different patterns of weather, known as climates: for example, dry summers, mild winters, and so on. The Sun is nearest and highest in the sky over the tropical regions on either side of the Equator. Also it shines directly down through the atmosphere here rather than at a low, slanting angle, so the atmosphere absorbs and scatters less of its heat. This is why tropical regions are hot all year. If dry winds blow over a tropical region they cause a tropical desert climate.

At the top and bottom of the Earth are polar regions where the Sun is farther away and lower in the sky, so these places are much colder. Between the tropics and poles are temperate lands which have warm summer and cool winters.

About a third of the Earth's land area has a desert or semi-desert climate.

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