An Overview of Climate Processes
Earth's Energy Balance
The Big Picture

While there are other external influences on weather and climate variability such as galactic cosmic rays (Svensmark, 2000), the primary force outside the Earth's internal system that drives the planet's weather and climate systems is the sun, about 150 million kilometers and eight minutes at the speed of light away from Earth. Burning 700 million tons of hydrogen and releasing 5 million tons of energy every second, the sun's generous supply of heat and light energizes the Earth's atmosphere and surface, sustaining life on this planet over billions of years. Visit the NOAA Space Environment Center for more on the sun's dynamics.

The amount of energy reaching the surface of the Earth can vary because of (1) internal processes within the sun, (2) changes in the Earth's orbit, such as the tilt of the axis (see Climate Science 100,000), or (3) changes within Earth's environment and climate system, such as major volcanic activity that cause dust to block the sun's energy or changes in the composition of the atmosphere.

The Earth's energy balance is complex depending on the type of radiation entering into the system (see figure below). Overall about 30% of energy overall is reflected back to space, with 70% being absorbed by the atmosphere and surface of the planet. Also see Graphic Overview of Earth's Climate System.

Next- the Greenhouse Planet
Image from Ruddiman, 2001 used by permission of W. H. Freeman & Co.