The Earth’s climate system

The Earth’s climate system includes the atmosphere (the air that surrounds the earth), hydrosphere (oceans, rivers, lakes), cryosphere (ice sheets, glaciers, sea ice), lithosphere (land surfaces, rocks) and biosphere (living things), and the ways they all interact.

The earth system is always in motion, and the elements of the global climate are always in conversation. When air, ice, water, rock and living things come into contact with one another they interact in many different ways. They exchange heat, gases like carbon dioxide (CO₂), and other materials, such as water and carbon. The movement of these elements between different parts of the earth system is what drives our climate.

Atmosphere

The Earth’s atmosphere surrounds the entire planet like a large, protective air bubble. Held in place around the Earth by gravity, the atmosphere is made up primarily of nitrogen (around 78 percent) and oxygen (21 percent). Argon, carbon dioxide, methane, water vapor and neon make up the remaining 1 percent. The air in the atmosphere is constantly moving, with warm air rising and cool air falling.

Hydrosphere

The hydrosphere refers to all of the water on the planet, from the great rivers that flow across continents to the entire global ocean, which comprises five interconnected ocean basins: the Atlantic, Pacific, Indian, Arctic and Southern Oceans. It includes water stored underground, in lakes, falling as rain and condensed in clouds.

Biosphere

The biosphere refers to the parts of the planet where life can survive and thrive. It includes the atmosphere, hydrosphere and lithosphere (also known as the abiotic or non-living part of the biosphere) and the living things that interact with them (this is known as the biotic or living part of the biosphere). All ecosystems and living creatures from microorganisms, algae and other plants to the largest predators on earth exist within the biosphere.

Cryosphere

The cryosphere refers to all of the ice on the planet. This includes snowfall, river ice, lake ice and sea ice. It also includes glaciers, ice sheets and ice shelves, and permafrost (permanently frozen ground).

Lithosphere

The lithosphere includes the rocks and minerals at the surface of the Earth, also known as the Earth’s crust. Mountains, deserts, valleys and volcanoes all form part of the lithosphere. While the lithosphere tends to move more slowly than the atmosphere and hydrosphere, it plays an important role in the climate over many thousands of years through volcanic eruptions, weathering and erosion.

North America climate map — Image credit: Ali Zifan

Climate and weather are closely linked. The main difference between them is time. Weather can change in a day, in a week, and from year to year. Climate takes a longer view, looking at the average temperature, humidity, wind, rainfall and other weather conditions over decades (usually 30 years or more).

The United States has many different climate zones, from the subtropical climate across much of the south-east, to the arid desert and alpine climates to the west. While the weather changes from day to day, it tends to change within a limited range. For example, Florida’s tropical climate makes huge snow storms unlikely and rainfall in the desert is rare.
Antarctica has a polar climate, with cold summers and extremely cold winters. Antarctica has been covered by a permanent ice sheet for more than 30 million years, and in winter at the South Pole, temperatures can drop to -76°F (-60°C).