Greenhouse Gases Meaning
In this article, we have discussed greenhouse gases' meaning. This article will help the students in making a short note on greenhouse gases. This Greenhouse effect article will help the students in clearing the concepts of greenhouse gases and global warming.
Greenhouse Gases Definition- Greenhouse gases definition explains the meaning of greenhouse gas. These are the gases that absorb and emit infrared radiation in the wavelength range emitted by the earth.
Let’s discuss which gas is called greenhouse gas? The examples of greenhouse gases in the earth’s atmosphere are:
Water
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Tropospheric ozone (O3)
Chlorofluorocarbons (CFCs)
Examples of greenhouse gases such as carbon dioxide (CO2) and water vapour (H2O) are natural greenhouse gases. Examples of greenhouse gas such as methane are anthropogenic emission greenhouse gases.
Contribution of Greenhouse Gases
89 % is contributed by the water vapour, 7 % is contributed by carbon dioxide, and the remaining percent is contributed by the other mentioned gases in the table.
What are Greenhouse Gas Emissions?
Greenhouse gas emissions are the emission of gases from various sources that cause global warming. The major emission source of greenhouse gases is an energy source and the least is contributed by the solvents.
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Percentage contribution to Global Warming
Before discussing this let’s discuss what is meant by greenhouse gases? Greenhouse gases are harmful environmental gases that are responsible for causing global warming.
Contribution
Carbon dioxide (CO2) > Methane (CH4) > Chlorofluorocarbons (CFCS) > Nitrous oxide (N2O)
Carbon dioxide contribution = 60%
Methane contribution = 20%
Chlorofluorocarbons contribution = 14%
Nitrous oxide contribution = 6%
Water vapour is not listed due to the amount being variable in nature and not anthropogenic.
Why is the Study of Greenhouse Gases necessary?
The answer to this question is similar to the question: what is the meaning of greenhouse gases? The greenhouse gases like methane, nitrous oxide, chloro fluoro carbons increases day by day due to the anthropogenic activities which trap the radiation of wavelength (7 to 13 micrometres) come under the atmospheric window and re-radiated back to the atmosphere and increase the temperature of the earth.
Carbon Dioxide
Absorbs radiation between 4 to 5 micrometre and 14-19 micrometre.
Concentration in pre-industrial time was 280 parts per million and in present-day its concentration is around 400 parts per million.
Residence time for carbon dioxide is 5 years to 200 years.
Methane
Methane absorbs radiation between 3 to 5 micrometre and 7 to 8.5 micrometre.
Concentration in pre-industrial time was 750 parts per billion and in present-day it is around 1800 parts per billion.
Nitrous Oxide
Nitrous oxide absorbs radiation between 3 to 5 micrometre and 7.5 to 9 micrometre.
Concentration in pre-industrial time was 7270 parts per billion and in present-day it is around 330 parts per billion.
Tropospheric Ozone
Ozone absorbs edition between 9-10.6 micrometre
Its concentration varies from place to place.
Halocarbons
Halocarbons absorb radiation around 9 micrometre in the frequency of the atmospheric window so that these are potent greenhouse gases and also play a role in depleting stratospheric ozone.
It can be divided into five categories:
Chlorofluorocarbons (CFCs)
Hydrochlorofluorocarbon (HCFCs)
Hydro Fluoro Carbon (HFCs)
Perfluorocarbon (FCs)
Halones
The ozone-depleting potential of halocarbons is
Bromine (BR) > chlorine (Cl) > fluorine (F)
Halones > CFCs > HCFCs
Global Warming Potential (GWP)
Global warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It allows a comparison to be made between the global warming impact over a specified particular GHGs and simultaneous emission of an equal mass of carbon dioxide (CO2).
Order of magnitude of Global Warming Potential
Sulphur hexafluoride (SF6) > Halocarbons > nitrous oxide (N2O) > methane (CH4)> carbon dioxide (CO2).
Did You Know?
Water provides a major contribution to the total greenhouse gases. Still, its contribution is not countable in causing global warming due to its variable concentration in the atmosphere.
The area of the electromagnetic spectrum where the atmosphere is transparent to specific wavelengths between 7 to 13.5 micrometers is called an atmospheric window.
FAQs on Greenhouse Gas
1. What is a greenhouse gas and what are its main examples?
A greenhouse gas is any gas in the atmosphere that has the molecular property to absorb and re-emit infrared radiation (heat). This process traps heat within the Earth's lower atmosphere, a phenomenon known as the greenhouse effect. The most significant greenhouse gases include Carbon Dioxide (CO₂), Methane (CH₄), Nitrous Oxide (N₂O), and various fluorinated gases like Chlorofluorocarbons (CFCs). Water vapour (H₂O) is also a major greenhouse gas.
2. What are the primary sources of the main greenhouse gases?
The primary sources of major greenhouse gases are linked to both natural processes and human activities (anthropogenic). For the academic year 2025-26, the key sources are:
- Carbon Dioxide (CO₂): Primarily from burning fossil fuels (coal, oil, and natural gas) for electricity and transportation, industrial processes, and deforestation.
- Methane (CH₄): From agricultural activities (like livestock digestion and rice cultivation), waste decomposition in landfills, and fossil fuel production.
- Nitrous Oxide (N₂O): Mainly from agricultural and industrial activities, combustion of fossil fuels, and treatment of wastewater.
- Fluorinated Gases (e.g., CFCs, HFCs): These are synthetic gases originating from industrial processes, refrigeration, and consumer products.
3. How do greenhouse gases actually trap heat in the atmosphere?
Greenhouse gases trap heat through a specific molecular mechanism. When sunlight warms the Earth's surface, the Earth radiates this energy back towards space as infrared radiation. The molecules of greenhouse gases are able to absorb this outgoing infrared radiation, causing them to vibrate. They then re-emit this radiation in all directions, including back towards the Earth's surface. This process prevents heat from escaping directly into space, effectively warming the lower atmosphere.
4. What is the crucial difference between the 'greenhouse effect' and 'global warming'?
The key difference lies in their nature and impact. The greenhouse effect is a natural and essential process where gases like CO₂ and water vapour trap heat to keep the Earth warm enough for life to exist. Without it, the planet would be too cold. Global warming, on the other hand, refers to the enhancement of this natural effect due to the excessive emission of greenhouse gases from human activities, leading to a rapid and detrimental increase in the Earth's average temperature.
5. Why isn't nitrogen (N₂), which makes up 78% of the atmosphere, considered a greenhouse gas?
Nitrogen (N₂) is not a greenhouse gas because of its molecular structure. Greenhouse gases must be able to absorb infrared radiation. This requires the molecule to have a changing dipole moment when it vibrates. Symmetrical diatomic molecules like nitrogen (N₂) and oxygen (O₂) do not have this property. Their simple, linear structure means they cannot bend or vibrate in a way that absorbs heat energy at infrared wavelengths, so they are transparent to it.
6. What does Global Warming Potential (GWP) measure and why is it important?
Global Warming Potential (GWP) is a relative measure used to compare the heat-trapping ability of different greenhouse gases over a specific time period, typically 100 years. It is benchmarked against carbon dioxide, which has a GWP of 1. For example, methane has a GWP of over 25, meaning one tonne of methane traps 25 times more heat than one tonne of CO₂ over a century. GWP is crucial for policymakers as it helps in understanding the climate impact of different emissions and prioritising reduction efforts.
7. Why is water vapour, a major greenhouse gas, often excluded from climate change policy discussions?
While water vapour is the most abundant greenhouse gas, it is typically excluded from policy discussions for two main reasons. First, its concentration in the atmosphere is primarily controlled by temperature, not direct human emissions. It acts as a feedback mechanism—a warmer atmosphere holds more water vapour, which in turn enhances warming. Second, water vapour has a very short residence time in the atmosphere (about nine days) compared to gases like CO₂ (hundreds of years), meaning it doesn't accumulate in the same way.
8. How do chlorofluorocarbons (CFCs) impact the environment in two distinct ways?
Chlorofluorocarbons (CFCs) are potent environmental threats due to their dual impact. Firstly, they are extremely powerful greenhouse gases with a very high Global Warming Potential (GWP), absorbing heat in the 'atmospheric window' where other gases do not. Secondly, when they reach the stratosphere, they undergo photolysis by UV radiation, releasing chlorine atoms. These chlorine atoms act as catalysts in a destructive cycle that breaks down stratospheric ozone (O₃), which is vital for protecting life on Earth from harmful UV rays.
