Understanding the role of solar radiation in the Earth's climate system can help us grasp important concepts such as:
The causes of the seasons:
Seasons are caused by the tilt of Earth's axis. The tilted axis means that the northern and southern parts of Earth do not receive equal amounts of solar radiation (energy per unit area). When the southern hemisphere is tilted toward the sun, it is summer in the southern hemisphere and winter in the northern hemisphere. (Principle 1c)
The reasons ice ages occur.
The ice ages were caused by changes in the distribution of solar radiation received over Earth's surface. The path of Earth's orbit is not constant. Variations in Earth's orbital path causes the solar radiation reaching any point on Earth's surface to change. (Principle 1d)
How the amount of energy emitted from the sun (sun's luminosity) changes over time.
The sun's output is not constant. Its luminosity (total energy emitted by the sun) has increased over geologic time, and varies slightly over shorter time scales.
Why recent climate warming has not been caused by increases in the sun's energy output.
The sun's energy output has not changed enough over the last decades to account for the increases in temperatures that have been observed during this same time. (Principle 1e)
Most forms of energy that humans use are derived from solar energy.
Many forms of energy that humans use ultimately derive from solar radiation, such as food, hydrocarbons (such as oil and natural gas), wind energy, hydroelectric power, and of course, solar energy.
Source: Climate Literacy & Energy Awareness Network