Glossary of Units for Carbon Dioxide Emissions Reporting
Grams of Carbon Dioxide Equivalent (gCO₂e)
- Definition: A small-scale unit used to measure greenhouse gas emissions, often applied to individual products, activities, or small systems.
- Example Use: Emissions per kilometer traveled by a car.
- Conversion: $$ 1 , \text{gCO₂e} = 0.000001 , \text{tCO₂e} $$.
Kilograms of Carbon Dioxide Equivalent (kgCO₂e)
- Definition: A mid-scale unit often used for household-level emissions or specific activities like energy use or waste generation.
- Example Use: Emissions from heating a home for one day.
- Conversion: $$ 1 , \text{kgCO₂e} = 0.001 , \text{tCO₂e} $$.
Tonnes of Carbon Dioxide Equivalent (tCO₂e)
- Definition: A standard unit for measuring greenhouse gas emissions on a larger scale, such as for businesses, projects, or small regions.
- Example Use: Annual emissions of a single car or the carbon footprint of an average household.
- Conversion: $$ 1 , \text{tCO₂e} = 1,000 , \text{kgCO₂e} $$.
Kilotonnes of Carbon Dioxide Equivalent (ktCO₂e)
- Definition: A larger unit used to report emissions from industrial facilities, cities, or sectors like transportation or energy production.
- Example Use: Annual emissions from a medium-sized power plant.
- Conversion: $$ 1 , \text{ktCO₂e} = 1,000 , \text{tCO₂e} = 1,000,000 , \text{kgCO₂e} $$.
Millions of Tonnes of Carbon Dioxide Equivalent (MtCO₂e)
- Definition: A very large unit used to express national or global greenhouse gas emissions or reductions.
- Example Use: Total annual emissions of a country or the impact of a large-scale climate policy.
- Conversion: $$ 1 , \text{MtCO₂e} = 1,000,000 , \text{tCO₂e} = 1,000 , \text{ktCO₂e} $$.
Gigatonnes of Carbon Dioxide Equivalent (GtCO₂e)
- Definition: The largest commonly used unit for global-scale reporting of greenhouse gas emissions and targets.
- Example Use: Total global annual emissions or cumulative reductions needed to meet international climate goals (like limiting warming to 1.5°C).
- Conversion: $$ 1 , \text{GtCO₂e} = 1,000 MtCO₂e = 1,000,000 ktCO₂e = 1,000,000,000 tCO₂e $$.
Carbon Dioxide Equivalent (CO₂e)
- Definition: A metric that expresses the impact of all greenhouse gases in terms of the equivalent amount of CO₂ that would produce the same global warming effect. It is calculated using the global warming potential (GWP) of each gas relative to CO₂.
- Formula: $$ CO₂e = (\text{Mass of Gas}) \times (\text{GWP of Gas}) $$
Summary Table
| Unit | Abbreviation | Scale | Conversion to tCO₂e | Example Use Case |
|---|---|---|---|---|
| Grams | gCO₂e | Small-scale | $$ 0.000001,\text{tCO₂e} $$ | Emissions per km driven by a car |
| Kilograms | kgCO₂e | Household-level | $$ 0.001,\text{tCO₂e} $$ | Daily household energy use |
| Tonnes | tCO₂e | Standard unit | $$ 1,\text{tCO₂e} $$ | Annual footprint of an average household |
| Kilotonnes | ktCO₂e | Industrial-level | $$ 1,000,\text{tCO₂e} $$ | Emissions from a power plant |
| Millions | MtCO₂e | National-level | $$ 1,000,000,\text{tCO₂e} $$ | Total annual emissions of a country |
| Gigatonnes | GtCO₂e | Global-scale | $$ 1,000,000,000,\text{tCO₂e} $$ | Global annual emissions |
This glossary focuses on units relevant to carbon dioxide and greenhouse gas reporting and provides essential context for understanding their applications across different scales.