Carbon Footprint Glossary

Quick answer: This glossary defines the essential terms used in carbon footprint measurement and climate science. From CO₂e to Scope 3 emissions, these are the definitions you need to understand your environmental impact.

Core Concepts

Carbon Footprint

The total amount of greenhouse gases (GHGs) generated by an individual, organization, event, or product. Measured in tonnes of CO₂ equivalent (tCO₂e) per year. Includes direct emissions (burning fuel) and indirect emissions (buying goods, using electricity).

CO₂e (Carbon Dioxide Equivalent)

A standard unit for measuring greenhouse gas impact. Different gases trap different amounts of heat — methane is 80x more potent than CO₂ over 20 years. CO₂e converts all GHGs into a single comparable number. For example, 1 kg of methane = 80 kg CO₂e.

Greenhouse Gas (GHG)

Any gas that traps heat in the atmosphere. The main GHGs are carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and fluorinated gases (F-gases). CO₂ from fossil fuels is the largest contributor to climate change.

Emissions Scopes

Scope 1 Emissions

Direct emissions from sources you own or control. For individuals: driving your car, heating your home with gas, cooking with gas. For companies: emissions from company vehicles, factories, and offices.

Scope 2 Emissions

Indirect emissions from purchased energy — primarily electricity and district heating/cooling. When you turn on a light, the power plant burns fuel on your behalf. These are your Scope 2 emissions.

Scope 3 Emissions

All other indirect emissions across the value chain. For individuals: the emissions embedded in food, clothing, electronics, and services you buy. For companies: supply chain, employee commuting, product use, and disposal. Scope 3 typically represents 70–90% of total emissions.

Measurement & Accounting

Emission Factor

A coefficient that converts activity data into emissions. Example: driving 1 km in a gasoline car × 0.192 kg CO₂e/km = your car emissions for that km. See our Emission Factors Reference for detailed values.

Life Cycle Assessment (LCA)

A method for evaluating the environmental impact of a product or service across its entire life — from raw material extraction to disposal ("cradle to grave"). LCA studies produce the emission factors used in carbon calculators.

Embodied Carbon

The total GHG emissions generated during the manufacturing of a product — before you use it. A smartphone's embodied carbon is ~70 kg CO₂e (mostly from mining rare earth metals and manufacturing). For buildings, embodied carbon includes concrete, steel, and construction.

Carbon Intensity

The amount of CO₂ emitted per unit of economic output or energy produced. A country's carbon intensity is its emissions per dollar of GDP. An electricity grid's carbon intensity is kg CO₂e per kWh generated.

Reduction Strategies

Carbon Neutral

A state where net carbon emissions equal zero — achieved by reducing emissions and purchasing carbon offsets for the remainder. Can apply to individuals, companies, or products. See our guide: Carbon Neutral vs Net Zero.

Net Zero

A more ambitious target than carbon neutral. Net zero means reducing emissions as close to zero as possible, with only residual emissions offset. Unlike carbon neutral, net zero requires actual deep reductions first, not just offsetting. Typically aligned with limiting warming to 1.5°C.

Carbon Offset

A credit purchased to compensate for emissions by funding projects that reduce or remove CO₂ elsewhere — like tree planting, renewable energy in developing countries, or direct air capture. 1 carbon offset = 1 tonne CO₂e reduced or removed.

Carbon Credit

A tradeable certificate representing the right to emit 1 tonne of CO₂e. Carbon credits are used in cap-and-trade systems and voluntary carbon markets. They differ from offsets — credits are often regulatory instruments.

Carbon Sink

A natural or artificial system that absorbs more CO₂ than it releases. Forests, oceans, and soil are natural carbon sinks. Technologies like Direct Air Capture (DAC) are engineered carbon sinks.

Related Terms

Global Warming Potential (GWP)

A measure of how much heat a greenhouse gas traps compared to CO₂ over a specific time period (usually 100 years). Methane has a GWP of ~28 (it traps 28x more heat than CO₂ over 100 years).

Decarbonization

The process of reducing carbon intensity across the economy — shifting from fossil fuels to renewable energy, electrifying transport, and improving efficiency.

Carbon Leakage

When emission reductions in one country lead to increases in another — typically when companies move production to countries with weaker climate regulations. Addressed through carbon border adjustment mechanisms.

Science-Based Targets (SBTs)

Emissions reduction targets set by companies that are consistent with what climate science says is needed to limit warming to 1.5°C or well below 2°C. Defined by the Science Based Targets initiative (SBTi).

Paris Agreement

The 2015 international treaty where 196 countries committed to limiting global warming to well below 2°C (preferably 1.5°C) above pre-industrial levels. Each country sets its own Nationally Determined Contributions (NDCs).

See also: What is a Carbon Footprint? and Carbon Neutral vs Net Zero for deeper explanations.