The Climate System
Our climate depends on the whole Earth system. The Sun, land (geosphere), ocean (hydrosphere), ice (cryosphere), and living organisms (biosphere) interact with the atmosphere in the climate system. Read on to learn more about the different parts of the system.
All energy in the Earth’s climate system originates from the Sun. Ninety-three million miles away, the Sun is a ball of nuclear reactions that constantly provides the top of our atmosphere with an average of 342 W/m2 of energy. If all of this energy was reflected straight back out to space, the average temperature of the Earth would be only -19°C (-1°F). Brrr! That's cold.
But not all of the energy is reflected back out to space. Some is absorbed, which keeps our planet from freezing. The ratio of the amount of energy reflected to the amount of energy absorbed is called albedo. Light colors reflect energy and dark colors absorb it. If all energy was reflected out to space, the albedo of the planet would be 1. If all energy was absorbed, the albedo of our planet would be 0. The average albedo of the Earth is approximately 0.3, which means that 30% of the energy is reflected and 70% is absorbed.
The Earth’s atmosphere is made up of 78% nitrogen and 21% oxygen. The remaining 1%, called trace gases, includes gases such as water vapor (H2O), ozone (O3), carbon dioxide (CO2) and methane (CH4) which absorb and re-emit infrared radiation, trapping energy on its way out to space and keeping the average temperature of the lower atmosphere approximately 14°C (57°F). This process is known as the greenhouse effect. However, today there are more of these heat-trapping gases, released by burning fossil fuels, which is warming the planet.
These gases also play other roles. For example, ozone (O3) protect life from harmful solar radiation in the ozone layer. Carbon dioxide (CO2) is used by plants for photosynthesis and water vapor (H2O) contributes clouds and precipitation to our weather.
Covering approximately 68% of the Earth’s surface, the ocean acts as a vast heat storage device in the climate system. Ocean circulation serves to transport heat from the equator to the poles. In addition, gases from the atmosphere can dissolve in the ocean and be stored for many years in the ocean depths. However, when carbon dioxide is disolved, seawater becomes more acidic which is harmful to marine life.
The Earth’s land masses affect both weather and climate. On a long geological timescale, changes in the distribution of land masses around the globe have had major effects on the movement of air around the planet, causing large changes in the Earth’s climate. On a much shorter timescale, changes in the surface of the land due to agriculture, forestry, and urbanization have made changes to the amount of energy that is being absorbed or reflected back to space. Major volcanic eruptions can also impact the Earth’s climate, as they spew gases and particles into the upper atmosphere, reflecting sunlight and altering atmospheric chemistry.
Nearly 70% of Earth’s freshwater is contained in ice caps, glaciers, and regions of permanent snow cover. With their bright white color, ice and snow have a high albedo so they reflect solar energy back to space. Ice also serves to insulate the ocean and land from the atmosphere, thus changing the dynamics of wind and weather processes.
Living organisms affect the Earth’s climate system. They can change the chemical makeup of the atmosphere by, for example, taking up carbon dioxide through photosynthesis as plants and algae do, and by adding chemicals to the atmosphere from pollution as humans do. Life also alters the colors, and thus the albedo, of the Earth’s surface.