A naturally-occurring gas in the Earth’s atmosphere, and also the main GHG released by human activities, such as burning fossil fuels and biomass, industrial processes and land-use change. These activities have led to a substantial increase in CO₂ atmospheric concentrations over the last century.

On a per-kilogram basis, methane, nitrous oxide and fluorinated gases all have higher climate change impact or global warming potential (GWP) compared to carbon dioxide.

For ease of understanding and consistency given these variations of GWP, scientists typically uses a unit measure called a ‘carbon dioxide equivalent’ or ‘CO₂ equivalent’, abbreviated as CO₂e to compare the emissions from various GHGs on the basis of their GWP by converting amounts of other gases to the equivalent amount of carbon dioxide.

Although these gases may have a higher GWP than carbon dioxide, carbon dioxide is the most abundant GHG emitted through human activities.

As defined in the Global Protocol for Community-scale Greenhouse Gas Inventories (GPC), a geographic boundary identifies the spatial dimensions of the inventory’s assessment boundary.

This geographic boundary defines the physical perimeter separating in-boundary emissions from out-of-boundary and transboundary emissions.

A quantified list of a city’s GHG emissions and sources.

Atmospheric gases of human or natural origin that absorb and reflect heat back in the form of thermal infrared radiation. This results in heat being trapped in the climate system.

The term ‘carbon’ is commonly used to refer to all GHGs, not just carbon dioxide (CO₂) and methane (CH₄). Other GHGs include nitrous oxide (N₂O), and certain fluorinated gases.

A colourless and odourless gas. The main sources of methane are agriculture and fossil fuel production, mainly natural gas. It is considered a GHG.

On a per-kilogram basis, methane, nitrous oxide and fluorinated gases all have higher climate change impact or global warming potential (GWP) compared to carbon dioxide.

For ease of understanding and consistency given these variations of GWP, scientists typically uses a unit measure called a ‘carbon dioxide equivalent’ or ‘CO₂ equivalent’, abbreviated as CO₂e to compare the emissions from various GHGs on the basis of their GWP by converting amounts of other gases to the equivalent amount of carbon dioxide.

Although these gases may have a higher GWP than carbon dioxide, carbon dioxide is the most abundant GHG emitted through human activities.

The boundaries that determine the direct and indirect emissions associated with operations owned or controlled by the reporting company.

This assessment allows a company to establish which operations and sources cause direct and indirect emissions, and to decide which indirect emissions to include that are a consequence of its operations.

The GHG emissions resulting from the operation of buildings, equipment and vehicles including use, management and maintenance activities.

Any GHG emissions that remain after a project or organisation has implemented all technically and economically feasible opportunities to decarbonise, in all scopes and from all sources.

Also called unavoidable emissions. This term may also be used regarding GHG emission source types that will be hard to abate over the long term.

Examples of this would evolve over time with new technologies and innovations. A current example would be for agriculture and shipping, two industries that are considered necessary to our survival and are likely to continue releasing GHGs into the atmosphere even after decarbonisation efforts (this may change in the future).

Quantifies the annual emissions resulting from consumption of all goods and services by the city inclusive of all lifecycle stages: production (upstream), use and end of life (downstream).

Condition in which an entity has balanced out the GHG emissions attributed to it via emissions reductions measures, GHG removals or offsets exclusively claimed by the entity, such that the net contribution to global GHG emissions is zero, over a declared time period.

Carbon neutrality does not require a specific rate of decarbonisation i.e. an actor could technically be increasing its emissions, but use offsets to achieve a net neutral status.

Processes that remove CO₂ from the atmosphere, such as by planting trees that absorb carbon, or by using processes to bind CO₂ with other molecules, with the potential to permanently or temporarily remove it out of the atmosphere.

The condition in which an entity reduces its GHG emissions to a residual level and neutralises any remaining GHG emissions over a declared period of time.

Neutralisation is achieved through removals that are exclusively claimed by the entity, within the value chain or by purchasing offsets.

Corporate GHG inventory

All direct emissions from sources that are owned or controlled by a company.

Geographic-based GHG Inventory

GHG emissions from sources located within a city boundary.

Corporate GHG inventory

Energy-related indirect emissions from the generation of purchased electricity, steam and heating/cooling consumed by a company.

Geographic-based GHG inventory

GHG emissions occurring as a consequence of the use of grid-supplied electricity, heat, steam and/or cooling within a city boundary.

Corporate GHG inventory

All other indirect emissions that are a consequence of the activities of a company.

Geographic-based GHG inventory

All other GHG emissions that occur outside a city boundary as a result of activities taking place within that boundary.

Clean energy is the generation of energy that does not produce GHGs while being consumed but its source of supply is finite/limited.

For example, nuclear energy generation is clean because it does not emit GHG, but it is not renewable because the material used to create the energy is limited.

Renewable energy is energy that is generated from natural sources that are replenished at a higher rate than they are consumed.

Sunlight and wind, for example, are such sources that are constantly being replenished and do not generate emissions into the atmosphere while being used to produce energy.

Consuming resources in the most effective way possible to ensure no waste is incurred, including electricity, water, natural resources etc.

The total amount of GHGs that are generated by the actions of an entity or individual.

The GHG emissions resulting from energy consumption to extract, refine, process, transport and fabricate a material or product (including buildings).

The GHG emissions resulting from the operation of buildings, equipment and vehicles including use, management and maintenance activities.