The greenhouse effect refers to the rise in the global average temperature of the earth.
The greenhouse effect is a process that occurs when gases in Earth’s atmosphere trap the Sun’s heat. This process makes Earth much warmer than it would be without an atmosphere. The greenhouse effect is one of the things that makes Earth a comfortable place to live. The process of global warming follows the given steps:
- Step 1: Solar radiation reaches the Earth’s atmosphere – some of this is reflected back into space(shortwave radiations).
- Step 2: The rest of the sun’s energy is absorbed by the land and the oceans, heating the Earth.
- Step 3: Heat radiates from Earth towards space (longwave radiation).
- Step 4: Some of this heat is trapped by greenhouse gases in the atmosphere, keeping the Earth warm enough to sustain life.
- Step 5: Human activities such as burning fossil fuels, agriculture, and land clearing are increasing the number of greenhouse gases released into the atmosphere.
- Step 6: This is trapping extra heat and causing the Earth’s temperature to rise.
Figure: GHG emission share
Gases that trap heat in the atmosphere are called greenhouse gases.
- Carbon dioxide (CO2): Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas, and oil), solid waste, trees and other biological materials, and also as a result of certain chemical reactions (e.g., manufacture of cement). Carbon dioxide is removed from the atmosphere (or “sequestered”) when it is absorbed by plants as part of the biological carbon cycle.
Figure: GWP of GHGs
- Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.
- Nitrous oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, combustion of fossil fuels and solid waste, as well as during treatment of wastewater.
- Fluorinated gases: Hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for stratosphericozone-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
- Sulphur hexafluoride
In 1997, the Kyoto Protocol (3rd COP) was concluded and established legally binding obligations for developed countries to reduce their greenhouse gas emissions.