Greenhouse gas is a gas that absorbs and emits infrared radiation. They absorb infrared energy (heat energy) emitted from the earth’s surface and reradiates it back to the earth’s surface. The greenhouse gases trap heat in the earth’s atmosphere and warm the planet.

What are Greenhouse Gases?

• Greenhouse gases are gases that trap heat in the atmosphere.
• Water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone are the primary greenhouse gases in the Earth’s atmosphere.
• Such gases in the atmosphere act as a blanket, trapping/absorbing some of the infrared radiation emitted by the earth and releasing some of it to it.
• However, any rise in such gases would result in more heat-trapping, increasing the earth’s temperature, as represented in global warming.
• Without greenhouse gases, the average temperature of the Earth’s surface would be around -18°C rather than the current average of 15°C.

Greenhouse Gases (GHGs)

• Carbon dioxide (CO₂): Carbon dioxide is emitted into the atmosphere through burning fossil fuels, solid waste, biological materials, and certain chemical reactions (e.g., cement manufacturing).
  Plants absorb carbon dioxide during the biological carbon cycle, removing it from the atmosphere.

Figure: GWP of GHGs

• Methane (CH₄): Methane is emitted during the production and transport of coal, natural gas, and oil.Methane emissions come from livestock, agricultural practices, and organic waste decay in landfills.
• Nitrous oxide (N₂O):Nitrous oxide is emitted from agricultural and industrial activities, fossil fuel combustion, solid waste, and wastewater treatment.
• Fluorinated gases: Industrial processes emit synthetic greenhouse gases like hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride.
  • Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons).
  • These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”).

• GHGs under Kyoto Protocol:
  • Carbon mono-oxide
  • nitrous oxide
  • methane
  • Sulphur hexafluoride
  • Hydrofluorocarbons
  • Perfluorocarbons

Causes of Greenhouse Effect

• The burning of Fossil fuels for domestic and industrial purposes releases carbon dioxide into the atmosphere which contributes to an increase in earth temperature.
• Plants and trees absorb carbon dioxide and emit oxygen. The cutting and burning of trees causes a significant increase in greenhouse gases, which raises the earth’s temperature.
• Fertilizers: Nitrous oxide, a component of fertilisers, contributes to the greenhouse effect in the atmosphere.
• Industries: Industries and factories produce hazardous gases that are release into the atmosphere.
• Landfills: Landfills also emit carbon dioxide and methane, which contribute to greenhouse gas emissions.

Effects of Increased Greenhouse Gases

• Global Warming: This is the gradual rise in the average temperature of the Earth’s atmosphere.
  • The increased production of greenhouse gases, like carbon dioxide and methane from fossil fuel combustion and human activities, is the main cause of this environmental problem.
• Ozone Layer Depletion: The ozone layer protects the earth from the sun’s harmful ultraviolet rays. It form in the stratosphere’s upper reaches.
  • The primary cause of this phenomenon is the accumulation of natural greenhouse gases like chlorofluorocarbons, carbon dioxide, methane, etc.
• Smog and Air Pollution: Smog forms when smoke and fog combine, resulting from natural and artificial factors.
  • Our Action Plan for cleaning River Ganga will bring benefits of pollution reduction and climate adaptation.
  • Automobile and industrial emissions, agricultural fires, natural forest fires, and chemical reactions are the major contributors to smog formation.
• Acidification of Water Bodies:
  Increasing greenhouse gases have caused acidification in most of the world’s water bodies.
  • The greenhouse gases combine with rainwater to form acid rain. This causes water bodies to become acidic.
  • Furthermore, rainwater carries contaminants with it and deposits them in rivers, streams, and lakes, causing acidification.

Global Initiatives to Reduce Greenhouse Gas Emissions

• Intergovernmental Panel on Climate Change (IPCC): The IPCC was established in 1988 by the WMO and UNEP to provide policymakers with periodic climate change assessments.
• United Nations Framework Convention on Climate Change: The agreement aimed to stabilize greenhouse gas concentrations and prevent dangerous intervention with the climate system.
• The Kyoto Protocol (KP): It is an international agreement that was adopted at the 3rd COP in 1997. Its primary goal was to cut global greenhouse gas emissions by at least 5% compared to 1990 levels by 2012.
• The reduction of greenhouse gases includes CO2, CH4, N2O, Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulfur Hexafluoride (SF6).

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