In the carbon market, everything revolves around an acronym that may seem technical but is fundamental: tCO₂e. It stands for tonne of carbon dioxide equivalent (CO₂e) — a standardized way of expressing the climate impact of different greenhouse gases in a single comparable unit.
But why not talk only about CO₂? Because there are other GHGs (Greenhouse Gases) with different levels of impact, such as methane (CH₄), nitrous oxide (N₂O), and fluorinated industrial gases. Each of them warms the atmosphere differently and over different timeframes. To make everything comparable, we convert these gases into a common basis: CO₂e.
The logic is simple:
Gas emissions × GWP = CO₂e.
GWP (Global Warming Potential) works as an equivalence factor. It indicates how much a gas warms the atmosphere compared to CO₂ over a given time horizon (such as 20 or 100 years).
Example considering a 100-year horizon (GWP100), according to methodologies from the Intergovernmental Panel on Climate Change (IPCC):
• 1 tonne of CH₄ ≈ 27 tCO₂e
• 1 tonne of N₂O ≈ 273 tCO₂e
(Values may vary depending on the report and methodology used.)
And why does this matter in the carbon market? Because, in general, 1 carbon credit corresponds to 1 tCO₂e. In other words, the entire logic of accounting, offsetting, and trading depends on this conversion.
A simple analogy: CO₂e is like converting currencies. GWP is the “exchange rate” that translates different gases into a common unit.
That’s why it’s always worth asking:
“CO₂e with which GWP and over what time period?” (for example, GWP100 = 100 years).
Understanding tCO₂e is not just a technical detail — it is the foundation of integrity and comparability in the carbon market.
