Climate is the average weather over many years. Climates around the planet will change if the things that control them change. To change global climate, either there is a change in the amount of heat that gets to the planet or the amount of heat that leaves the planet. For instance, warming climates are either because more heat is let into the Earth or because less heat is let out of the atmosphere.

The heat comes from the Sun. Sunlight travels through Earth’s atmosphere, heating up the land and oceans. The Sun affects climate when the amount of solar energy let into the system changes. Changes in Earth’s orbit over thousands of years and changes in the Sun’s intensity affect the amount of solar energy that reaches the Earth.

Heat leaves the Earth when the planet surface radiates heat away. Greenhouse gases in our atmosphere allow the lower atmosphere to absorb heat that is radiated from the Earth’s surface, trapping heat within the Earth system. Without any greenhouse gases, Earth would be a frozen world. However, the amount of greenhouse gases in our atmosphere is on the rise, causing temperature to climb.

Living things affect climate by altering the amount of sunlight that is absorbed at the Earth surface and the amount of greenhouse gases in our atmosphere. Some organisms and processes help global cooling while others help global warming depending on their role in the carbon cycle.

There are many different factors that make climate more complicated. There are probably some complications that scientists have not yet identified. One complicating factor is how clouds affect climate change. Some types of clouds may help warming, while others may help cooling.

Courtesy of USGS Astrogeology Research Program