![]() ![]() We are already increasing the amount of energy that bounces back to the Earth. Scientists say that if CO2 doubles, it could raise the average global temperature of the Earth between two and five degrees Celsius. We have now reached about 414 ppm, so we are on the way to doubling the amount of CO2 in the atmosphere by the end of this century. Before the industrial revolution, the amount of CO2 in the atmosphere was about 288 ppm. The burning of fossil fuels affects the concentration of CO2 in the atmosphere. The higher the greenhouse gas, the more effective it is at trapping heat from the Earth’s surface. In addition, water vapor is concentrated lower in the atmosphere, whereas CO2 mixes well all the way to about 50 kilometers up. But while water vapor is the dominant greenhouse gas in our atmosphere, it has “windows” that allow some of the infrared energy to escape without being absorbed. Because of the greenhouse effect created by these trace gases, the average temperature of the Earth is around 15˚C, or 59˚F, which allows for life to exist.ĬO2 makes up only about 0.04% of the atmosphere, and water vapor can vary from 0 to 4%. This trapping of heat is what we call the greenhouse effect. After these gases absorb the energy, they emit half of it back to Earth and half of it into space, trapping some of the heat within the atmosphere. Of the remaining 1 percent, the main molecules that can absorb infrared radiation are CO2 and water vapor, because their atoms are able to vibrate in just the right way to absorb the energy that the Earth gives off. Without gases like these to absorb the energy, our planet’s average surface temperature would have been near zero degrees Fahrenheit.Ībout 99 percent of the atmosphere is made of oxygen and nitrogen, which cannot absorb the infrared radiation the Earth emits. Water vapor and CO2, however, act like a cap, making it more difficult for Earth to get rid of this energy. Yochanan Kushnir is a research professor at Lamont-Doherty Earth Observatory, in the Division of Oceans and Climate PhysicsĮarth absorbs energy from sunlight, but as the surface warms, it also emits energy in the form of infrared radiation (which we know of as heat) out into space.
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