What are the Greenhouse Gases?

Green house gases are the atmospheric gases that allow the sunlight to enter freely into the atmosphere. This can be explained from the fact that these gases absorb and retain the energy from the infrared radiation.


When sunlight strikes the surface of the Earth, some of the energy is reflected back in the form of heat or the infrared radiation. Greenhouse gases absorb this infrared radiation to trap heat in the atmosphere.


Greenhouse gases can absorb and emit infrared radiation within the thermal infrared range. The major greenhouse gases are Carbon dioxide (CO2), Water vapour (H2O), Methane (CH4), Nitrous oxide (N2O), Chlorofluoro carbons and perfluorocarbons (CFCs and PFCs).


What are greenhouse gases?

What are greenhouse gases? (Image source: sxc.hu)

The concept of greenhouse gases can be well understood from the greenhouse.

What is a greenhouse?

Greenhouse is a structure, where plants are grown. Significant feature of the structure is that the energy absorbed from the sunlight is trapped inside the greenhouse, through re-radiation of thermal energy in the infrared spectrum by the plants and the soil, to which the closed glass or roof is partly opaque.


The glass panels or the roofs of the greenhouses can be compared with the greenhouse gases, which traps the heat absorbed from the sun.


Major Greenhouse Gases:

Carbon dioxide (CO2)

It is the most important greenhouse gas emitted by the humans. The major sources of this greenhouse gas are:

  • Volcanic eruptions and respiration of organic matter in natural eco systems. (Know more about what are volcanoes)
  • Deforestation and burning trees. (Read details of Causes and Effects of Deforestation)
  • Burning fossils to produce electricity.
  • Burning or combustion of gasoline and other fuels to run vehicles.
  • Industrial and manufacturing processes like producing cement and chemicals.


Water Capour (H2O)

Many a times, the contribution of water vapour as a greenhouse gas is considered controversial. But later it was proved scientifically as the most powerful greenhouse gas, present in the atmosphere.


Considerably, when the planet gets heated up, it leads to the evaporation of more water and since the water vapour, in itself is a greenhouse gas leads to more heating of the planet. Hence it acts as a positive loop of heating.



  • Evaporation and sublimation of water from major water bodies like oceans and seas.
  • Clouds contribute major percentage of water vapour in the atmosphere.
  • Natural processes like geothermal activities and volcanic eruptions also produce water vapour to get released into the atmosphere.
  • Human and animal activities produce water vapour to release into the atmosphere.


Methane (CH4)

It is the most significant greenhouse gas other than carbon dioxide. It can trap over 20 times more heat than carbon dioxide.



  • Produced by anaerobic decay of organic materials in agricultural fields, wetlands and landfills.
  • Producing and transporting of natural gas, may lead to release of methane gas into atmosphere, when subjected to any leakage.
  • Mining coal can lead to release of methane in the coal mines.
  • Raising livestock:  Most of the animals like cow and sheep, release methane during the process of digestion. Manure also releases methane, when decayed.
  • Fossil fuel combustion also releases significant amount of methane.


Nitrous oxide (N2O)

This gas can trap heat about 298 times more than the same amount of carbon dioxide can do.



  • Industrial and manufacturing processes produce some amount of nitrous oxide.
  • It is emitted during agricultural activities, like applying fertilizers.
  • Fossil fuel combustion and animal waste management also accounts for the release of significant amount of nitrous oxide.


Chlorofluoro carbons and perfluorocarbons (CFCs and PFCs):

These compounds contain the elements of carbon and fluorine that produce greenhouse gases on destabilisation. The gases, produced may last for thousand years in the atmosphere. Depending on the gas, they can trap the heat from a few hundred times to 23,000 times more than the same amount of carbon dioxide can do.



  • Refrigerators, coolers and air conditioners leak fluorinated gases into the atmosphere.
  • Industrial and manufacturing processes like semiconductor manufacturing also lead to the release of carbons into the atmosphere.
  • They are produced as the by product of the aluminium smelting.


In addition to the above mentioned gases, there are significant number of gases like ozone that act as the greenhouse gases.


Aerosols Vs Greenhouse gases:

Aerosol is a suspension in any medium like air, liquid or solid particles. Clouds can  be considered as an example. Even, when we sneeze, we considerably create an aerosol.


Aerosol emissions include:

  • Dust lifted directly from the traffic, coal mines, sewage etc.
  • Tiny particles emitted when wood, oil or coal is burnt.


Aerosols reflect or absorb light, depending on the colour of the particles, they are composed of. They also provide “condensation nucleus” , that affects the clouds that contribute to the greenhouse effect and also accounts for the cooling of the Earth’s surface by preventing the sunlight to reach the ground.


Hence it can be considered as the part of the heating caused by the greenhouse gases, are controlled by the cooling of the aerosols. But when the lifetime of the aerosols is considered, they cannot accumulate in the atmosphere for longer durations. Hence the effects of the aerosols cannot control the effects of greenhouse gases on the long term.


Non greenhouse gases:

Although there exist various other gases in the atmosphere like nitrogen, oxygen and argon, they are not considered as the greenhouse gases. This can be explained from the fact that molecules of such elements have no net charge in their dipole moment when they vibrate and hence unaffected by the infrared radiations.


Greenhouse gases and radiation balance: Greenhouse effect

Earth supports the life on it mostly due to the climatic balance it achieves, due to the atmosphere. The balance between the amount of radiation absorbed to the amount of radiation emitted creates a unique environment on the planet to support life.


Too much absorption of radiation can lead to the extreme warming of the planet and too much emitting would result in extreme cold, which happens in the case of other planets.


Greenhouse gases play an important role in maintaining such a balance through the process of re-radiating the absorbed radiation. Hence balance of the greenhouse gases are required to be maintained in the atmosphere.


This phenomenon of thermal radiation from the surface of the planet, absorbed by the green house gases to emit radiation in all directions, to produce a warm air blanket around the planet is known as the greenhouse effect. Besides the planet Earth, various other planets like Venus and Mars also exhibit the greenhouse effect.


The effect was proposed by Joseph Fourier in 1824 and was first investigated by Svante Arrhenius in 1896.


A change in the balance of the greenhouse gases may lead to change in the radiation balance and hence leads to disruption in the heat balance of the planet.


Global warming:

Global WarmingGlobal warming is the rise in the average temperature level of the Earth’s atmosphere and oceans. The mean surface temperature of the Earth has increased by about 0.8 degrees centigrade, since 1980. Similarly, significant temperature changes are recorded around the world, depicting the phenomenon of global warming. This gradual increase in the surface temperature of the Earth has adverse effects on the climate change like melting of polar ice, which have to be avoided to protect the life on the planet Earth.


 Effects of global warming:

  • Reduction in global food production.
  • Habitat Inundation.
  • Melting of ice.
  • Reduction in the availability of fresh water sources.
  • Rise in the water level in the oceans that may lead to floods.
  • Endangered species would become extinct, disrupting the balance in the ecosystem.


Greenhouse gases and global warming:

Considerable rise in the amount of greenhouse gases can be considered as the significant reason for the effect of global warming. The concentrations of carbon dioxide and methane have increased by 36% and 148% since 1750. This increase in levels of carbon dioxide and methane at an alarming rate is to be checked immediately to control global warming.


Greenhouse gas protocol (GHG Protocol):

To tackle the climate change greenhouse gas emissions must be monitored and controlled.  A partnership has been established between the World Resource Institute and World Business Council for Sustainable Development, known as GHG protocol to understand, quantify and control greenhouse gas emissions. It provides the accounting framework for nearly, every GHG standard and program in the world.


Steps to reduce greenhouse gas emissions:

Significantly, greenhouse gas emissions can be controlled by individuals and a revolution can also be brought, initiating our own minds.


Some of the steps that can be taken to minimize greenhouse gas emissions are:

  • Growing own foods, using eco-friendly products, buying energy efficient appliances and using renewable sources of energy. Read about different types  of energy sources.
  • Reduce the use of refrigerators and air conditioners.
  • Use septic vent pipe filter, to reduce greenhouse gas emissions from the septic tank.
  • Use rechargeable batteries.
  • Pollute less water and take short showers and conserve water. (Different types of pollution)
  • Use electricity and appliances effectively.
  • Walk short distances and use public transport as much as possible.
  • Buy sustainable and organically farmed food.
  • Avoid using plastic. Read disadvantages of plastic
  • Most of them all, educate yourself about greenhouse gases, global warming and other environmental related issues and share it with everyone to conserve our only planet EARTH.