Final answer:
The Earth's greenhouse effect is caused by direct sunlight heating the ground and air, which is then re-emitted as infrared heat trapped by greenhouse gases in the atmosphere. This effect maintains warm temperatures conducive to life. The direct angle of sunlight in one hemisphere during different times of the year also influences this warming effect.
Step-by-step explanation:
The Earth receives direct sunlight that heats the ground and air, resulting in a phenomenon known as the greenhouse effect. This process is crucial for maintaining life-sustaining temperatures on our planet. The sunlight that reaches Earth is a mixture of various wavelengths including ultraviolet, visible light, and infrared. The ground absorbs this solar energy and then re-emits it as heat, or infrared radiation, back into the atmosphere. Greenhouse gases such as water vapor, methane, and carbon dioxide (CO₂) within the atmosphere are efficient at absorbing this heat, preventing it from escaping into space. Instead, they re-radiate the heat back towards the surface, essentially trapping it and keeping the Earth's surface warmer than it would otherwise be.
Direct sunlight is most intense when the Sun is favoring one hemisphere, causing sunlight to hit at a more direct angle and heating the Earth's surface more effectively. This contributes to seasonal temperature variations. It's important to note that increased concentrations of greenhouse gases can lead to an enhanced greenhouse effect, which is a driving factor behind global warming.