What are greenhouse gases and CO2 equivalent (CO2e)?
Which gases warm the planet, how CO2 equivalent and global warming potential work, why reports use different GWP values, and where India's emissions come from.
Which greenhouse gases matter most?
International climate rules and the GHG Protocol track seven gases or gas groups: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF6) and nitrogen trifluoride (NF3).
| Gas | Common human sources in India | Average time in the air (IPCC AR6) | GWP over 100 years (IPCC AR6) |
|---|---|---|---|
| Carbon dioxide (CO2) | Coal power, petrol and diesel, cement, cutting forests | No single value; part stays for centuries or longer | 1 |
| Methane (CH4) | Cattle and buffalo digestion, flooded rice fields, landfills, coal mines, gas leaks | 11.8 years | 27.0 (non-fossil) or 29.8 (fossil) |
| Nitrous oxide (N2O) | Nitrogen fertilisers such as urea, manure | 109 years | 273 |
| HFC-32 | Refrigerant in many newer air conditioners | 5.4 years | 771 |
| HFC-134a | Refrigerant in car ACs and fridges | 14.0 years | 1,530 |
| PFC-14 (CF4) | Aluminium smelting | 50,000 years | 7,380 |
| Sulphur hexafluoride (SF6) | Electrical switchgear | (not in summary table) | 24,300 |
| Nitrogen trifluoride (NF3) | Electronics and solar panel manufacturing | (not in summary table) | 17,400 |
Sources: lifetimes from IPCC AR6 Working Group I, Chapter 7, Table 7.15 (2021); GWP values from the GHG Protocol "IPCC Global Warming Potential Values", version 2.0, August 2024, which reproduces the AR6 values.
What about water vapour and ozone?
Water vapour is the largest natural contributor to the greenhouse effect, but people do not control it directly. Its amount depends mainly on temperature: a warmer atmosphere holds more moisture, which adds more warming. For this reason, scientists treat it as a feedback that amplifies warming caused by other gases, and it is not counted in emission inventories. Ozone near the ground also warms the climate, but it forms from other pollutants rather than being released directly.
Sources: IPCC AR6 Working Group I, Summary for Policymakers (2021); IPCC AR6 Working Group I, Chapter 7: The Earth's Energy Budget, Climate Feedbacks and Climate Sensitivity (2021); IPCC AR6 Working Group III, Annex I: Glossary (2022); GHG Protocol, IPCC Global Warming Potential Values, Version 2.0 (August 2024); MoEFCC, India First Biennial Transparency Report (BTR-1) to the UNFCCC; MoEFCC, India Fourth Biennial Update Report (BUR-4), December 2024; UNFCCC Decision 18/CMA.1, Modalities, procedures and guidelines for the transparency framework; UNFCCC Decision 5/CMA.3, Guidance for operationalizing the modalities, procedures and guidelines for the enhanced transparency framework; Press Information Bureau / PM India: Cabinet approves ratification of Kigali Amendment to the Montreal Protocol (August 2021); 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 2, Chapter 1
This article was prepared with AI assistance and checked by the GreenEye team against the sources shown in each section.
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