What are greenhouse gases?
The Earth’s atmosphere is composed of many gases. The main three are known as oxygen, nitrogen and argon, which comprise of approximately 99.5% of all the gas molecules in the world. These gases do not present any significant effects towards the atmosphere, but there are some minor gases in that remaining <1% of all air molecules (most of which are water vapor molecules) that do somewhat contribute to a natural phenomena known as the greenhouse effect. These gases are therefore known as the greenhouse gases.
The following table below from the NOAA Earth System Research Laboratory Global Monitoring Division shows the composition of Earth's dry atmosphere in the year 2009.
The following table below from the NOAA Earth System Research Laboratory Global Monitoring Division shows the composition of Earth's dry atmosphere in the year 2009.
The greenhouse effect
Heat energy provided from solar radiation (light source of the Sun) is the reason why Earth can sustain life presently. When this energy hits the surface of the Earth, it reflects back into the atmosphere at a different wavelength, so this outgoing energy becomes infrared radiation. In the air, greenhouse gases such as carbon dioxide and methane are gases which trap and absorb some of this escaping energy and disperse it in all directions within the atmosphere, maintaining the warmth of the planet. Thanks to this phenomena, it is the reason why humans, animals and plants all alike do not freeze to death from extremely low temperatures.
To the right is a diagram (also from NOAA, ESRL, the same source as the table above) which illustrates the greenhouse effect.
Since the beginning of the Industrial Revolution (round about the late 1700's), the concentration of greenhouse gases present in the atmosphere has rocketed by an estimate of 30%, most significantly carbon dioxide. Before the revolution, activities that contribute to the emission of carbon dioxide (such as the burning of fossil fuels) wasn't very intense. Thus, with the oceans and vegetation, the carbon dioxide level 300 years ago was capable of staying in balance. The following line graph from the United States Environmental Protection Agency (EPA) at the bottom left shows the total U.S. greenhouse gas emissions in a period of 20 years from 1990 - 2010, and the pie chart beside it (also from the same source) depicts the total U.S. greenhouse gas emissions based upon its economic sector as of 2010.
To the right is a diagram (also from NOAA, ESRL, the same source as the table above) which illustrates the greenhouse effect.
Since the beginning of the Industrial Revolution (round about the late 1700's), the concentration of greenhouse gases present in the atmosphere has rocketed by an estimate of 30%, most significantly carbon dioxide. Before the revolution, activities that contribute to the emission of carbon dioxide (such as the burning of fossil fuels) wasn't very intense. Thus, with the oceans and vegetation, the carbon dioxide level 300 years ago was capable of staying in balance. The following line graph from the United States Environmental Protection Agency (EPA) at the bottom left shows the total U.S. greenhouse gas emissions in a period of 20 years from 1990 - 2010, and the pie chart beside it (also from the same source) depicts the total U.S. greenhouse gas emissions based upon its economic sector as of 2010.