Understanding the Seven Greenhouse Gases Covered by the Kyoto Protocol

The Kyoto Protocol, an international treaty aimed at reducing greenhouse gas emissions, covers seven main greenhouse gases, often referred to as “direct greenhouse gases.” They are:

1. Carbon dioxide (CO2)
2. Methane (CH4)
3. Nitrous oxide (N2O)
4. Hydrofluorocarbons (HFCs)
5. Perfluorocarbons (PFCs)
6. Sulphur hexafluoride (SF6)
7. Nitrogen trifluoride (NF3)

Carbon Dioxide (CO2):
CO2 is the most abundant greenhouse gas emitted by human activities. Major sources include the combustion of fossil fuels (coal, oil, and natural gas) for energy, deforestation, and certain industrial processes. CO2 emissions contribute significantly to global warming and climate change.

Methane (CH4):
Methane is a potent greenhouse gas with a much higher heat-trapping ability per molecule than CO2, although it’s less abundant in the atmosphere. Major sources include livestock digestion (enteric fermentation), rice paddies, landfills, and natural gas production and distribution. Methane emissions contribute to global warming and also have implications for air quality and human health.

Nitrous Oxide (N2O):
Nitrous oxide is another potent greenhouse gas with a much higher heat-trapping ability per molecule than CO2. Sources include agricultural activities (such as fertiliser use and soil management), industrial processes, and combustion of fossil fuels. Nitrous oxide emissions contribute to global warming and also play a role in the depletion of the ozone layer.

Hydrofluorocarbons (HFCs):
HFCs are synthetic gases used primarily as refrigerants in air conditioning and refrigeration, as well as in foam blowing agents and aerosols. Although they are less abundant than CO2, HFCs have a much higher global warming potential per molecule. HFC emissions have been increasing rapidly due to the phase-out of ozone-depleting substances under the Montreal Protocol, leading to concerns about their contribution to climate change.

Perfluorocarbons (PFCs):
PFCs are synthetic gases used mainly in the electronics industry, as well as in aluminium production and semiconductor manufacturing. They have extremely high global warming potentials and can persist in the atmosphere for thousands of years.
PFC emissions are relatively small compared to other greenhouse gases but still contribute to climate change.

Sulphur Hexafluoride (SF6):
SF6 is a synthetic gas primarily used in electrical transmission and distribution equipment, as well as in the semiconductor industry. It has an extremely high global warming potential and can persist in the atmosphere for thousands of years. SF6 emissions are relatively small but have a significant impact due to their potency.

Nitrogen Trifluoride (NF3):
NF3 is a synthetic gas used in the production of semiconductors and flat-panel displays. It has a very high global warming potential, even higher than some other fluorinated gases like SF6. NF3 emissions are relatively small but are of concern due to their potency and increasing use in electronics manufacturing. 

These greenhouse gases, though varying in abundance and potency, all are significant contributors to climate change due to their ability to trap heat in the atmosphere. Monitoring and reducing their emissions are critical components of international efforts to mitigate climate change and limit its impacts.

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