Greenhouse Gases List

Terms like 'global warming', 'greenhouse effect' and 'greenhouse gases' are being heard much more frequently these days. Not surprising, because we have already begun to notice minor variations in the climatic patterns these days, which are just going to worsen with time. But what exactly do we mean by greenhouse effect? What are the greenhouse gases and how do they affect us?

Greenhouse Gases Definition
The term 'greenhouse gases' is used to refer to the gases present in the atmosphere which absorb the radiations and emit them within the thermal infrared range. These gases affect the temperature of the earth significantly, in fact it is assumed that the absence of these gases would have made the temperature of the earth surface around 59 degree Fahrenheit colder than what it is at present. The most prominent greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, ozone and CFCs.

Greenhouse Effect
Not everything is good about these greenhouse gases. These greenhouse gases tend to trap the solar radiations, which eventually leads to a rise in the surface temperature. This heating of Earth's surface is known as greenhouse effect or greenhouse warming. Although they heat up the surface of the Earth, they simultaneously cool the stratosphere, which eventually triggers ozone layer depletion. Ozone layer is very important for us, considering the vital role it plays by barring the UV rays from entering the atmosphere of the Earth. Read more on facts about the greenhouse effect.

Greenhouse Gases List
As we mentioned earlier greenhouse gases are the gases which trap the solar radiations and trigger a rise in temperature levels on the planet. There are various greenhouse gases, the most prominent ones being carbon dioxide and chlorofluorocarbons (CFCs). But the greenhouse gases list also includes a few gases we know, but we didn't know that they were termed as the greenhouse gases. Some examples are methane, nitrous oxide and, of course, water vapor.

Water Vapor: Water vapor is the gaseous form of water, which is produced due to evaporation of water and/or sublimation of ice. The atmosphere of the Earth witnesses continuous production of water vapor due to immense amount of evaporation from water bodies. Eventually, this water vapor is removed from the atmosphere by the process of condensation. Water vapor, approximately constitutes about 33 to 66 percent of greenhouse gases, thus becoming the most prominent constituents of greenhouse gases list. Anthropogenic factors, i.e. human activity does contribute in formation of water vapor, but the amount of vapor produced in this case is relatively negligible.

Carbon Dioxide: Carbon dioxide, a chemical compound, that constitutes of two atoms of oxygen, covalently bonded to a single atom of carbon, turn into a gas at standard temperature and pressure. The chemical formula for carbon dioxide is CO². Carbon dioxide is produced in the several processes, prominent ones being respiration in plants and animals (including human beings) and combustion of fossil fuels. Carbon dioxide in small amounts is also produced in several geothermal processes, such as eruption of a volcano. Recent estimates reveal, that the concentration of carbon dioxide in the Earth's atmosphere has increased to 387 parts per million by volume. This gas features second in the greenhouse gases list, constituting 9 to 26 percent of greenhouse gases. Read more on global warming and carbon dioxide.

Methane: Another prominent gas featuring in the greenhouse gases list is methane. The molecular formula of methane is CH⁴. It is one of the most potent greenhouse gases with a global warming potential of 25 averaged over a century. The capacity of methane to trap heat is 20 times more than that of carbon dioxide. This gas is produced in large amounts during a process known as methanogenesis. It's assumed that the Earth's crust contains huge deposits of methane gas, a part of which is let out in the process of mining, thus adding to the greenhouse effect. Studies reveal that the amount of methane in the atmosphere has gone up from 700 parts per billion in 1750 to 1745 parts per billion in 1998, which constitutes 4 to 9 percent of greenhouse gases.

Nitrous Oxide: Nitrous oxide is another important greenhouse gas, which can cause a high impact on global temperatures. The chemical formula of nitrous oxide, also referred to as NOX or laughing gas, is N²O. This gas is an important, naturally occurring regulator of the stratospheric ozone, which tends to react with the ozone and contribute to greenhouse effect. Averaged over a century, the impact of nitrous oxide per unit weight is 298 times more than that of carbon dioxide.

Ozone: Another gas prominently featuring in the greenhouse gases list is ozone constituting approximately 3 to 7 percent of greenhouse gases. Ozone, in upper troposphere acts as a greenhouse gas, while at ground level it acts as an air pollutant, harmful for respiratory system of animals and humans alike. As a greenhouse gas, ozone absorbs the infra red energy that is emitted by the earth. The irregular patter of ozone concentration across the globe, makes it difficult for us to determine the potential of this gas, but it's assumed that the radiative forcing of ozone present in troposphere is approximately 25 percent more than that of carbon dioxide.

Haloalkanes: Not all haloalkanes are harmful, typically those haloalkanes which contain bromine and chlorine lead to depletion on ozone layer. The haloalkanes, also referred to as alkyl halides, consist of a group of chemical compounds comprising of alkanes and one or more than one halogen linked to make them a type of organic halide. Chlorofluorocarbons (CFCs) form the most widely known haloalkanes, which are harmful for the environment.

Other than these, gases such as sulfur hexafluoride, hydrofluorocarbons, nitrogen trifluoride and perfluorocarbons are also included in the greenhouse gases list. But owing to their presence in small quantities, these gases are not considered to be as important as major greenhouse gases such as carbon dioxide and methane.

List of Greenhouse Gases in the Atmosphere
Going through this table will provide you a better picture about the various constituents of greenhouse effect mentioned in the greenhouse gases list mentioned above.

Greenhouse Gases	Lifetime in Years
Carbon Dioxide	200
Methane	12
Nitrous Oxide	120
CFC-11	45
CFC-12	100
CFC-13	640
CFC-113	85
CFC-114	300
CFC-115	1700
HFC-23	264
HFC-32	5.6
HFC-41	3.7
HFC-43-10mee	17.1
HFC-125	32.6
HFC-134	10.6
HFC-134a	14.6
HFC-152a	1.5
HFC-143	3.8
HFC-143a	48.3
HFC-227ea	36.5
HFC-236fa	209
HFC-245ca	6.6
Perfluoromethane	50,000
Perfluorethane	10,000
Perfluoropropane	2,600
Perfluorobutane	2,600
Perfluoropentane	4,100
Perfluorohexane	3,200
Sulphur hexafluoride	3,200

It is difficult to determine the global warming potential of greenhouse gases, such as water vapor and ozone, and hence they are excluded from the table. But that doesn't mean they are not important greenhouse gases. In fact, these gases together constitute a large part of the greenhouse gases and have tremendous global warming potential, and hence cannot be ignored.

Global Warming Potential
Global warming potential is an estimate of how much a given mass of any of the aforementioned greenhouse gases will contribute to the hazards of global warming. The efficiency of the molecule and the atmospheric lifetime of the gas determines the global warming potential of the particular greenhouse gas.

The greenhouse gases list given above comprises of all the harmful gases which lead to greenhouse effect. Greenhouse effect has been considered to be a nuisance for the environment for a long time. In fact several countries have banned the use of products which lead to emission of harmful gases such as CFCs, after taking into consideration the harmful effects of these gases. Some nations have also accepted initiatives, such as carbon trading, in order to curb the menace of global warming. Governing bodies such as Intergovernmental Panel on Climate Change (IPCC) are striving for the betterment of the environment, but these efforts will only be successful when 'we' understand the seriousness of environmental issues such as global warming or climate change, and thrive to make the planet Earth a better place for the generations to follow.