What are greenhouse gases and where do they come from ?
Water vapor is a greenhouse gas that rapidly circulates in and out of the atmosphere. The major greenhouse gas that humans are adding to the atmosphere is carbon dioxide, CO2, which remains in the atmosphere a century or more. The second largest greenhouse gas being emitted by humans is methane, CH4, which is around 20 times more powerful than CO2.
Water vapor is a greenhouse gas that rapidly circulates in and out of the atmosphere. The major greenhouse gas that humans are adding to the atmosphere is carbon dioxide, CO2, which remains in the atmosphere a century or more. The second largest greenhouse gas being emitted by humans is methane, CH4, which is around 20 times more powerful than CO2. Much of this comes from agricultural sources such as farm animals and rice paddies. Nitrous oxide is another large greenhouse contributor. CFCs, the ozone depleting substances that are now being phased out, as well as their replacement, HCFCs, are also powerful greenhouse gases. Roughly three-quarters of human-caused greenhouse warming comes from the burning of fossil fuels – coal, oil and gas. Most of the remainder comes from deforestation, primarily of the tropical rainforests.
