Gases in Earth\'s atmosphere, such as carbon dioxide and water vapor, act like a
ID: 1515817 • Letter: G
Question
Gases in Earth's atmosphere, such as carbon dioxide and water vapor, act like a blanket that reduces the amount of energy that Earth radiates into space. This phenomenon is called the greenhouse effect. Without the greenhouse effect, most of Earth would have a climate comparable to that of the polar or subpolar regions. What would Earth's mean surface temperature be, in the absence of the gases causing the greenhouse effect?
The Sun continually irradiates our upper atmosphere with an intensity of about 1360 W/m2. About 30% of this energy is reflected back into space, leaving an average of950 W/m2 to be absorbed by the surface area of Earth that is exposed to the Sun. This exposed area is REarth2, the Earth's circular cross section that intercepts the sunlight. All objects, including Earth, emit radiation at a rate proportional to the fourth power of the surface temperature (T4) in kelvins (K). Thus, the radiation is emitted from Earth's surface, which as a sphere has the area 4REarth2.
To maintain a constant temperature, Earth's radiation rate must equal its energy absorption rate from the Sun. A fairly simple calculation indicates that the two rates are equal when the average surface temperature of Earth is 255 K, or about 0 F. However, Earth's mean surface temperature is much warmer than thatabout 288 K. The calculations neglected the effect of greenhouse gases in the atmosphere. These gases absorb infrared radiation emitted by Earth and reflect some of it back to Earth. Thus, Earth emits less energy into space than it would without greenhouse gases. The energy absorbed from the Sun and the reduced energy emitted into space have caused the Earth to warm to its mean surface temperature of 288 K.
Over the past two centuries the concentration of carbon dioxide in our atmosphere has increased from a pre-industrial level of about 270 parts per million to 380 parts per million. This increase in carbon dioxide and other greenhouse gases has been caused by the burning of fossil fuels and the removal of forests, which absorb carbon dioxide. The carbon dioxide concentration in the atmosphere is expected to reach 600-700 parts per million by 2100. If that occurs, it will be warmer in 2100 than at any time in the last half million
Because of the increased temperature of Earth's surface (288 K compared to 255 K) due to the greenhouse effect, its energy emission rate has increased significantly. Why hasn't Earth cooled down as a result?
Because of the increased temperature of Earth's surface (288 compared to 255 ) due to the greenhouse effect, its energy emission rate has increased significantly. Why hasn't Earth cooled down as a result?
It is cooling down. Earth's atmosphere absorbs some of the outgoing radiation and emits it back to Earth's surface. There is a long delay between the change in temperature and the increased rate of radiation by Earth. The Sun absorbs much of Earth's extra radiation, and the Sun is warming and emitting more radiation. All of the above are correct.Explanation / Answer
Earth's atmosphere absorbs some of the outgoing radiation and emits it back to Earth's surface.
Due to heavy CO2 in the atmosphere, the reflected energy from earth is obsorbed by this CO2 and again reflected by it. That is why Earth gets more heated.
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