The climate of the world

What factors control the climate of the world?

The world’s weather is dependent on several major atmospheric and ocean circulation systems. The four main controlling factors are:

  • the world’s circulation system
  • the ocean conveyor belt system
  • the effects of latitude and altitude
  • the greenhouse effect

The world’s circulation system

Warm air rises at the Equator, where the Sun is highest in the sky, and travels to around 30º north where it cools and sinks to the surface before returning to the tropics. This movement is known as the Hadley cell.

The Ferrel cell is found between the Hadley and Polar cells and lies between 60º north and 30º north. This is where the UK lays.

The Polar cell is much smaller. Cold air sinks at the North Pole, before flowing south at the surface. Here it is warmed by contact with land/ocean around 60º north, where it rises.

At the Equator there is an area of low pressure, due to the rising and expanding air. At around 30º north the sinking air creates an area of high pressure.

The world’s circulation system. The UK receives winds from the south-west. This often brings warm, mostly subtropical air to our shores, keeping Britain mild in the winter and warm in the summer.
The prevailing wind direction in the UK is from the south-west

The ocean conveyor belt system

The world’s oceans also play an important role in redistributing energy around the globe and controlling climates.

Energy is moved from areas of surplus to those of deficit, with warm currents transporting warm water pole-wards and cold currents taking colder water to lower latitudes.

Water is transferred around the world as part of what is known as the ocean conveyor belt system or the thermohaline circulation system.

The oceans cover 67 per cent of the Earth's surface, and therefore receive 67 per cent of the Sun's energy that reaches Earth. Oceans hold onto this heat for longer than land does, and the ocean currents move this heat around, from the tropics to higher latitudes.

Within the UK, the North Atlantic Drift is a current of warm water that moves in a north-easterly direction and maintains Britain’s warm temperate climate - without this current, Britain would potentially plunge into an ice age.

The world’s ocean conveyor belt system (Global Thermohaline Cycle). The UK receives a warm current of water called the North Atlantic Drift.

Effects of latitude and altitude

Latitude, or distance from the Equator

Temperatures drop the further an area is from the Equator due to the curvature of the Earth. In areas closer to the poles, sunlight has a larger area of atmosphere to pass through, and the Sun is at a lower angle in the sky. As a result, more energy is lost and temperatures are cooler. The UK sits between the latitude of 50 to 58 degrees north of the Equator.

In addition, the presence of ice and snow nearer the poles causes the albedo effect, meaning that more solar energy is reflected, also contributing to the cold.

Altitude, or height above sea level

Locations at a higher altitude have colder temperatures. Temperature usually decreases by 1°C for every 100 metres in altitude. The temperature on the top of Mount Snowdon (approximately 1000 m above sea level) would be approximately 10 degrees colder than at the nearby coastal town of Porthmadog.