| ### 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**: $$ 1 \, \text{gCO₂e} = 0.000001 \, \text{tCO₂e} $$. | |
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| #### **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**: $$ 1 \, \text{kgCO₂e} = 0.001 \, \text{tCO₂e} $$. | |
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| #### **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**: $$ 1 \, \text{tCO₂e} = 1,000 \, \text{kgCO₂e} $$. | |
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| #### **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**: $$ 1 \, \text{ktCO₂e} = 1,000 \, \text{tCO₂e} = 1,000,000 \, \text{kgCO₂e} $$. | |
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| #### **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**: $$ 1 \, \text{MtCO₂e} = 1,000,000 \, \text{tCO₂e} = 1,000 \, \text{ktCO₂e} $$. | |
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| #### **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**: $$ 1 \, \text{GtCO₂e} = 1,000 MtCO₂e = 1,000,000 ktCO₂e = 1,000,000,000 tCO₂e $$. | |
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| #### **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**: | |
| $$ | |
| CO₂e = (\text{Mass of Gas}) \times (\text{GWP of Gas}) | |
| $$ | |
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| ### 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. |