CO2e

CO2e, or carbon dioxide equivalent, is a metric used to compare and aggregate the climate impact of different greenhouse gases (GHGs) by expressing their emissions in terms of the amount of CO2 that would cause the same amount of warming over a specified time horizon, usually 100 years. This allows diverse gases to be analyzed on a common scale.

Calculation generally involves multiplying the amount of each gas emitted by its global warming potential (GWP) for the chosen horizon, then summing the results. CO2 has a GWP of 1 by definition. Methane (CH4) has a GWP in the tens, typically around 28–36 over 100 years; nitrous oxide (N2O) around 265–298; and many fluorinated gases range from hundreds to thousands. GWP values come from assessments by bodies such as the IPCC and can vary with horizon and gas version.

Applications include carbon footprinting, life-cycle assessment, product and corporate reporting, and national inventories. CO2e provides a single metric to compare the overall climate impact of activities, products, or organizations and to communicate results in consistent terms.

Limitations should be noted: the GWP is a simplification that aggregates diverse gas behaviors, does not capture differences in atmospheric lifetime or regional effects, and depends on the chosen time horizon and gas list. Consequently, CO2e results can vary with methodological choices, and should be interpreted alongside detailed gas-specific information. Sources and standards for calculations include the IPCC guidelines and frameworks such as the Greenhouse Gas Protocol and ISO 14064.