Final answer:
The greenhouse effect describes how greenhouse gases trap heat within the Earth's atmosphere, leading to a warming of the planet. While these gases allow incoming sunlight to pass through, they effectively absorb and re-radiate the infrared energy back to Earth, resulting in an increase in surface temperature.
Step-by-step explanation:
The greenhouse effect is a natural process whereby greenhouse gases in the Earth's atmosphere trap heat. These gases, which include water vapor, carbon dioxide, methane, nitrous oxide, and ozone, are transparent to the visible light from the sun but are effective at absorbing infrared radiation (heat) that is re-emitted from the Earth's surface. As sunlight reaches the Earth, it warms the surface, which then radiates energy in the infrared spectrum. Greenhouse gases absorb this infrared radiation and re-radiate it in all directions, including back towards the Earth's surface, which effectively warms the planet.
It's important to understand that the incoming sunlight is mostly in the visible and ultraviolet range, which passes easily through the atmosphere. The Earth then converts this energy to infrared light as it cools, but because the Earth is much cooler than the sun (with an average temperature of 300 K compared to the Sun's 5800 K), the energy is emitted at longer, infrared wavelengths. Greenhouse gases are better at trapping these longer wavelengths, leading to the warming effect. This is why increased concentrations of these gases lead to higher global temperatures, a phenomenon known as global warming.
This trapping of heat does not counteract evenly with the radiation of heat back into space because the Earth's re-emitted infrared energy is at a different wavelength that is more readily absorbed by greenhouse gases, leading to an imbalance resulting in the net warming of the planet.