Emissions
Emissions are substances released into the air, water, or soil by human activity. In climate reporting the word means greenhouse gas emissions, measured in tonnes of carbon dioxide equivalent (tCO₂e) and split into Scope 1, Scope 2, and Scope 3.
A company's emissions come from three places. Scope 1 is what it burns or leaks directly: gas in boilers, diesel in owned vehicles, refrigerant escaping from cooling equipment. Scope 2 is the electricity, steam, heating, and cooling it buys. Scope 3 is everything else in the value chain, from purchased goods to business travel to the use of sold products.
Each source is converted to tCO₂e by multiplying an activity quantity, such as therms of gas or kilowatt-hours of electricity, by an emission factor. Different gases are converted to a common unit using global warming potential, so methane and refrigerants can be added to CO₂ in a single total.
Scope 3 is usually the largest share and the least reliable, because it depends on supplier data that often does not exist yet. That is why reported emissions carry a data quality assessment alongside the number. An auditor checks the method and the evidence, not only the total, so the useful output of an emissions calculation is a figure with its source documents attached.
Frequently asked questions
What are emissions? +
Emissions are substances released into the environment by human activity. In climate reporting the term means greenhouse gases released into the atmosphere, measured in tonnes of CO₂ equivalent.
What is the difference between Scope 1, 2, and 3 emissions? +
Scope 1 covers direct emissions from sources a company owns or controls. Scope 2 covers purchased electricity, steam, heating, and cooling. Scope 3 covers the rest of the value chain, including purchased goods, travel, and sold products.
How are emissions calculated? +
An activity quantity, such as litres of fuel or kilowatt-hours of electricity, is multiplied by an emission factor. Gases other than CO₂ are converted using global warming potential so everything can be reported as tCO₂e.
Related terms
Scope 1 Emissions
Scope 1 emissions are direct greenhouse gas emissions from sources that an organization owns or controls. This includes combustion of fossil fuels in owned boilers, furnaces, and vehicles; process emissions from manufacturing; and fugitive emissions such as refrigerant leaks and methane from owned landfills.
Scope 2 Emissions
Scope 2 emissions are indirect greenhouse gas emissions from the generation of purchased electricity, steam, heating, and cooling consumed by an organization. They are called 'indirect' because the emissions physically occur at the power plant or utility, not at the reporting company's facilities.
Scope 3 Emissions
Scope 3 emissions are all indirect greenhouse gas emissions that occur in an organization's value chain — both upstream (suppliers, purchased goods, business travel, employee commuting) and downstream (product use, end-of-life treatment, investments). Scope 3 typically represents 70–90% of a company's total carbon footprint.
Greenhouse Gas (GHG)
Greenhouse gases are atmospheric gases that trap infrared radiation and warm the Earth's surface. The six main GHGs covered by the Kyoto Protocol are carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆). The Kigali Amendment added nitrogen trifluoride (NF₃).
Emission Factor
An emission factor is a coefficient that converts an activity measurement — such as litres of fuel burned, kilowatt-hours of electricity consumed, or dollars spent on a commodity — into a quantity of greenhouse gas emissions, typically expressed in kilograms or tonnes of CO₂ equivalent (tCO₂e).
tCO₂e (Tonnes of CO₂ Equivalent)
tCO₂e — tonnes of carbon dioxide equivalent — is the standard unit for expressing greenhouse gas emissions. It normalizes different greenhouse gases (methane, nitrous oxide, HFCs, etc.) to their equivalent warming impact relative to CO₂ using global warming potentials (GWPs), allowing them to be summed into a single comparable metric.
Carbon Accounting
Carbon accounting is the systematic process of measuring, recording, and reporting the greenhouse gas (GHG) emissions produced by an organization, product, or activity. It follows standardized methodologies — most commonly the GHG Protocol — to quantify emissions across Scope 1 (direct), Scope 2 (purchased energy), and Scope 3 (value chain) categories, producing an auditable inventory that underpins disclosure, reduction planning, and regulatory compliance.