Carbon and emissions glossary: the terms, defined

A way of calculating emissions from a physical quantity of activity, such as litres of fuel, kWh of electricity or kilometres travelled, multiplied by a conversion factor per unit.

The UK government conversion factors are activity-based: per kWh, per litre, per kilometre.

Where there is not enough data for an activity-based calculation, DESNZ says a spend-based method may be used and the method reported.

Scope 3 category 6: emissions from flights, trains, hotels, hire cars and staff cars used on business mileage. It is an upstream category.

The DESNZ conversion factors give factors for air, rail and other travel per passenger-kilometre, and the report should say which set it used.

Carbon dioxide equivalent: each greenhouse gas weighted by its global warming potential, so that carbon dioxide, methane, nitrous oxide and the other gases can be added into one number.

The UK government factors use the IPCC’s fifth assessment values for methane (28) and nitrous oxide (265), because these are consistent with UNFCCC reporting and the UK inventory.

A number that turns something you measured into something you report: multiply litres of diesel, or kWh of grid electricity, by the right factor and the answer is kilograms of carbon dioxide equivalent.

The UK government publishes a set each year, and the 2026 factors are for activity data that falls entirely or mostly within 2026.

They are sometimes still called the Defra or BEIS factors; DESNZ publishes them now.

Scope 3 categories 9 to 15: what happens after a company sells, from downstream transport, processing and use of sold products to their end-of-life treatment, downstream leased assets, franchises and investments.

They are the other half of Scope 3 from upstream emissions, which are categories 1 to 8. Which categories are large depends on the business model.

Scope 3 category 7: staff travelling between home and work, with homeworking counted where the company chooses to count it. It is an upstream category.

The DESNZ conversion factors include a homeworking worksheet alongside the transport factors.

A ratio of emissions to a measure of business activity, such as tonnes of CO2e per £ million of turnover or per square metre of floor area.

SECR requires at least one: the report must state a ratio that expresses annual emissions in relation to a quantifiable factor associated with the company’s activities, and the company chooses the factor.

In the Science Based Targets initiative’s criteria, a science-based emissions target that runs five to ten years from the date it is submitted for validation, with a base year no earlier than 2015.

Under the Corporate Net-Zero Standard V2.0, which is published but not yet in force, the timeframe is exactly five years.

Unintended releases from equipment the company owns or controls, such as refrigerant leaking from air conditioning or methane from gas equipment.

They are Scope 1 emissions.

The DESNZ conversion factors include factors for refrigerants and process gases.

A way of estimating emissions by multiplying money spent by an average emissions-per-pound factor.

It is fast across a whole ledger, but it cannot tell an efficient supplier from an inefficient one, so it finds the large categories rather than showing a supplier’s reduction.

DESNZ says to use it where there is not enough data for activity-based methods, and to report the method used.

Tonnes of carbon dioxide equivalent, the unit in which emissions are reported.

The conversion factors give kilograms of CO2e, so divide by a thousand when the report uses tonnes.

SECR asks for the annual quantity of emissions in tonnes of carbon dioxide equivalent.

Scope 3 categories 1 to 8: purchased goods and services, capital goods, fuel- and energy-related activities, upstream transportation and distribution, waste generated in operations, business travel, employee commuting and upstream leased assets.