Frequently asked questions

CO2e, or carbon dioxide equivalent, is one common unit that shows how much warming a mix of greenhouse gases causes, expressed as the amount of carbon dioxide that would cause similar warming. For example, 1 tonne of non-fossil methane is about 27 tonnes CO2e using the IPCC AR6 100-year value.

CO2 is one gas, carbon dioxide, while CO2e is a unit that adds all greenhouse gases together after converting them to the warming effect of carbon dioxide. A footprint given in CO2 alone leaves out methane, nitrous oxide and fluorinated gases.

Carbon dioxide causes the most human-made warming overall, because it is released in by far the largest amounts and part of it stays in the air for centuries. In India it made up 78.9% of greenhouse gas emissions in 2022 (BTR-1, MoEFCC).

Kilogram for kilogram, methane traps much more heat: about 27 to 30 times more over 100 years and about 80 times more over 20 years, according to IPCC AR6. But it stays in the air for only about 12 years, and far less of it is released, so carbon dioxide still causes more total warming.

In the IPCC Sixth Assessment Report (AR6, 2021), the 100-year GWP of methane is 27.0 for non-fossil sources and 29.8 for fossil sources. The older AR5 value of 28 is still used for national reports under the Paris Agreement, and India's BUR-4 used the AR2 value of 21.

Yes, water vapour is a greenhouse gas and the largest natural part of the greenhouse effect, but it acts as a feedback rather than a driver. Its amount rises as the air warms because of other gases, so it is not counted in emission inventories.

Yes, in two ways: the electricity it uses is mostly made from coal in India, and its refrigerant, often an HFC, is a strong greenhouse gas if it leaks. For example, 1 kg of HFC-32 equals 771 kg CO2e using the IPCC AR6 100-year value.

Carbon (C) counts only the carbon atoms, while carbon dioxide (CO2) counts the whole molecule, so 1 tonne of carbon equals about 3.67 tonnes of CO2. Forest and soil studies often report carbon, so convert before comparing with emissions.