CO2e or CO2 equivalent is the unit of measurement for the impact of different greenhouse gases (GHGs) on global warming in terms of the amount of CO2 calculated on the basis of the Global Warming Potential index.

Thanks to this unit of measurement, we can in fact calculate with a single value the environmental impact that an activity, event or product would cause by emitting many different greenhouse gases, considering them in the equivalent amount of carbon dioxide.

The Global Warming Potential is a fixed value that expresses any greenhouse gas in terms of CO2.

For example, the GWP of methane is 28, that of nitrous oxide is 265. So while one tonne of methane corresponds to 28 tonnes of CO2e, one tonne of nitrous oxide corresponds to 265 tonnes of CO2e.

You can find the conversion tables of CO2 equivalents prepared by the IPCC here and those prepared by Greenhouse Gas Protocol, based on the IPCC’s fifth report, here.

Man-made climate change is caused by the release of certain types of gases into the earth’s atmosphere. These gases, called greenhouse gases (GHGs), are many and varied.

The United Nations Intergovernmental Panel on Climate Change (IPCC) has developed the Global Warming Potential (GWP), which is an index that measures the warming potential absorbed by a given amount of a greenhouse gas in comparison with that absorbed by the same mass of CO2 over a given period of time, usually 100 years.

The main greenhouse gas is carbon dioxide or carbon dioxide (CO2), a gas that is emitted every time fossil fuels are burned. It is followed by methane gas (CH4), which is mainly produced by agricultural activities and landfills. Methane gas has 28 times the polluting capacity of CO2 when comparing the climate impact the two gases will have over 100 years.

Even more impactful in terms of climate change are refrigerant gases and nitrous oxide (N2O), released into the atmosphere in smaller quantities and mainly from industrial and agricultural processes. The gas N2O is about 265 times more potent than carbon dioxide over the course of a century.

A single element or activity can cause the emission of a combination of several different greenhouse gases in varying quantities. In these cases, calculating the carbon footprint can become quite complicated. To simplify the study of greenhouse gas emissions and to make the emissions from different types of gases comparable, the term CO2e (carbon dioxide equivalent) is used as the unit of measurement.

The difference between the terms and the respective emissions of CO2 and CO2 equivalent is therefore rather intuitive to understand: CO2 refers exclusively to carbon dioxide emissions, while CO2 equivalent comprises the measurement of the impact of the different greenhouse gases considered in the CO2 equivalent value.