CO2 emissions are measured in many different ways, some of those are described below.
- Annual production-based CO2 emissions, also known as territorial emissions, are emissions - from activities like fossil-fuel production & burning, cement production, gas flaring, etc. - produced within a country’s boundaries in a particular year. These are used in international policies for reporting & setting targets for emissions. They are important because they directly impact the amount of greenhouse gases in the atmosphere.
- Average per capita production-based CO2 emissions are calculated by dividing the annual production-based CO2 emissions of a country in a particular year by its population. These can be misleading as some oil producing countries have low populations.
- Cumulative production-based CO2 emissions are calculated by adding up a country’s annual production-based CO2 emissions over time. These are calculated because a large fraction of CO2 remains in the atmosphere for hundreds of years once emitted.
- Annual consumption-based CO2 emissions, also known as emissions adjusted for trade and sometimes as a country's carbon footprint, provide the correction when emissions produced in one part of the world are used to provide goods & services in another part of the world. These are calculated for a country for a particular year using the formula:
Annual production-based CO2 emissions - (minus) CO2 emissions embedded in exported goods + (plus) CO2 emissions embedded in imported goods
- Average per capita consumption-based CO2 emissions are calculated by dividing the annual consumption-based CO2 emissions of a country in a particular year by its population. They reflect the average consumption and lifestyle choices of the country’s citizens.
- International shipping emissions are not included in a country's emissions. The responsibility for measuring & reducing emissions in this sector is assigned to the United Nations (UN) agency International Maritime Organisation (IMO).
- International aviation emissions are not included in a country's emissions. The responsibility for measuring & reducing the emissions in this sector is assigned to the United Nations (UN) agency International Civil Aviation Organisation (ICAO).
Ritchie H and Roser M, “CO₂ and Other Greenhouse Gas Emissions” (Our World in Data, 2020). See here for complete list of data sources
Timperley J, “In-Depth: Will Countries Finally Agree a Climate Deal for Shipping?” (Carbon Brief, 2018)