What do the figures in CO2 calculations and CO2 equivalents mean?
What does «CO2» mean?
CO2 is the chemical formula for carbon dioxide. It is produced when fossil fuels such as oil, gas or coal are burned. For example, when driving a car, heating a home or producing food. Carbon dioxide is the greenhouse gas most commonly emitted by humans and can remain in the atmosphere for several hundred years. It is considered the most important contributor to the greenhouse effect, i.e. global warming.
In addition to CO2, other gases also contribute to global warming, such as methane (CH4), nitrous oxide (N2O) and technical gases such as sulphur hexafluoride (SF6). Some of these have an even greater impact on the climate than CO2. However, as carbon dioxide is released in the greatest quantities, we usually refer to CO2 reduction.
In order to make the effects of these different gases comparable, the unit CO2 equivalent (CO2e) was introduced. It shows how much a particular gas contributes to global warming compared to CO2. This allows all greenhouse gases to be converted into a common unit and compared.
What does «CO2 equivalent» mean?
The word «equivalent» means equal or comparable.
CO2 equivalent (CO2e) is therefore not a real mass, but a unit of calculation. It shows how much another greenhouse gas warms the Earth compared to CO2.
Example:
1 kilogram of methane (CH4) warms the Earth about 27 times more than 1 kilogram of CO2.
→ 1 kg CH4 = 27 kg CO2e.
This figure comes from the so-called *global warming potential* (GWP). It is an international value that indicates how much a gas contributes to warming over a certain period of time (usually 100 years).
GasGWP (over 100 years) Lifespan in the atmosphere CO21until 1.000 yearsCH4 (Methan)27–30approx. 12 yearsN2O (nitrous oxide)273approx. 120 yearsSF6 (sulphur hexafluoride)25.200over 3.000 years
These values come from the Intergovernmental Panel on Climate Change (IPCC) and are updated regularly.
How are CO2 equivalents calculated?
The basic formula is:
Emissions = Amount of gas × Global Warming Potential (GWP)
Emissions are the amounts of greenhouse gases that are released into the atmosphere as a result of our actions. For example, when driving a car, heating our homes or consuming electricity. These gases trap heat and thus contribute to global warming.
Examples:
1 liter of diesel → *2.65 kg CO2 × GWP 1 = 2.65 kg CO2e
1 kg of methane → 1 kg CH4 × GWP 27 = 27 kg CO2e
This is how different gases are converted into a common figure so that their impact on the climate can be better compared.
*One liter of diesel produces around 2.65 kg of CO2, because when it is burned, the carbon it contains reacts with oxygen from the air to produce this amount of carbon dioxide.
Why are CO2e figures important?
CO2e figures help us understand how much our actions affect the climate. They show how much greenhouse gas is released during certain activities and create a common language for comparing emissions.
Not only private individuals, but also companies, cities and countries use CO2e figures to calculate their carbon footprint, measure progress and set climate targets. Without this comparison system, it would be almost impossible to evaluate the success of climate protection measures.
In short:
CO2e figures make climate protection tangible. They translate complex processes into clear, understandable data – so we can see where we can start to effectively reduce emissions.