docs/units-glossary.md

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.