Why do greenhouse gases not block solar radiation and daily solar radiation values high at the poles in summer?
Greenhouse gases do not block solar radiation, but they do absorb and re-emit infrared radiation, which is the type of radiation that the Earth emits after being warmed by the sun. This re-emitted infrared radiation is what traps heat in the atmosphere and causes the greenhouse effect.
The reason why greenhouse gases do not block solar radiation is that they interact with light at different wavelengths. Solar radiation is mostly composed of visible light and ultraviolet light, which have shorter wavelengths than infrared radiation. Greenhouse gases, such as carbon dioxide and methane, absorb infrared radiation at specific wavelengths. When they absorb this radiation, they gain energy and vibrate more. This vibration can cause the molecules to re-emit the infrared radiation in a different direction. Some of this re-emitted radiation is directed back towards the Earth, which is what traps heat in the atmosphere.
The amount of solar radiation that reaches the Earth's surface varies depending on the latitude and the time of year. At the poles, the sun is always low in the sky, even during the summer months. This means that the sunlight has to travel through a thicker layer of atmosphere to reach the Earth's surface. As the sunlight travels through the atmosphere, some of it is scattered and absorbed. This is why the sun appears to be red or orange when it is low in the sky. The amount of solar radiation that reaches the Earth's surface at the poles is also lower than the amount of solar radiation that reaches the Earth's surface at the equator. This is because the Earth is tilted on its axis, and the poles are always farther away from the sun than the equator.
As you can see, the average daily solar radiation values are highest at the equator and lowest at the poles. This is because the equator receives the most direct sunlight from the sun. The poles receive the least direct sunlight from the sun, and they also receive less sunlight overall because they are farther away from the sun.
You have already learned that Earth's atmosphere is composed primarily of nitrogen and oxygen. These gases are transparent to incoming solar radiation. They are also transparent to outgoing infrared radiation, which means that they do not absorb or emit solar or infrared radiation. CO2 molecules don't really interact with sunlight's wavelengths. Only after the Earth absorbs sunlight and reemits the energy as infrared waves can the CO2 and other greenhouse gases absorb the energy. When sunlight strikes the earth's surface, some of it radiates back toward space as infrared radiation (heat). Greenhouse gases absorb this infrared radiation and trap its heat in the atmosphere, creating a greenhouse effect that results in global warming and climate change. Not all gas molecules are able to absorb IR radiation. For example, nitrogen (N2) and oxygen (O2), which make up more than 90% of Earth's atmosphere, do not absorb infrared photons. CO2 molecules can vibrate in ways that simpler nitrogen and oxygen molecules cannot, which allows CO2 molecules to capture the IR photons. Greenhouse gases in the atmosphere repeatedly absorb and re-radiate infrared radiation (heat). High clouds trap long wave, infrared radiation (heat) re-radiated from Earth's surface. However, low clouds reflect incoming sunlight (shortwave radiation) back to space. Greenhouse gases in the atmosphere repeatedly absorb and re-radiate infrared radiation (heat). High clouds trap long wave, infrared radiation (heat) re-radiated from Earth's surface. However, low clouds reflect incoming sunlight (shortwave radiation) back to space. At the summer solstice of the northern hemisphere, daily insolation reaches a maximum at the North Pole because of the 24-hour-long solar day. At the winter solstice, the sun does not rise above the horizon north of about 66.5°, where solar insolation is zero. A location receives its most intense radiation during summer, and its least intense radiation during winter. Summer occurs when a hemisphere is tilted towards the sun. This tilt causes the hemisphere to get more direct sunlight for more hours a day, and temperatures tend to be warmer.
- Badges
- Science topic
- Similar topics
- Biological Science
- Biota
- Eukaryota
- Fungi