Carbon Dioxide Equivalent (CO2e or CO2eq) meaning

Carbon dioxide equivalent (CO2e or CO2eq) is the standard way to express, as a single figure, the combined climate impact of different greenhouse gases in legal, regulatory and contractual practice. It converts emissions of gases such as methane, nitrous oxide and fluorinated gases into the amount of carbon dioxide that would cause the same warming over a stated time horizon, using global warming potential (GWP) factors published by the IPCC. Unless specified otherwise, a 100‑year GWP is used. The term is used and, in many instruments, defined or cross‑referenced in UK and Irish legislation and guidance, including the UK climate change Act regime, the UK Emissions Trading Scheme, EU/UK monitoring and reporting rules, Streamlined Energy and Carbon Reporting under the Companies Act 2006, and Irish climate and ETS legislation. Each instrument specifies which GWP table applies. Figures are typically presented as tonnes CO2e and are central to statutory GHG reporting, emissions trading, environmental permitting, public procurement requirements, contract carbon accounting (including offsets), sustainability‑linked finance and corporate due diligence. Usage and meaning are broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland. Always check the applicable regulation for the correct GWP factors and time horizon.