Where do the three scopes come from?

The scopes come from the GHG Protocol Corporate Accounting and Reporting Standard (revised edition, 2004), developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). Two later documents add the detail:

• the Scope 2 Guidance (2015), on counting purchased electricity and energy, and
• the Corporate Value Chain (Scope 3) Standard (2011), on value-chain emissions.

The Corporate Standard covers seven gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF6) and nitrogen trifluoride (NF3). All are converted into tonnes of CO2 equivalent (tCO2e) so they can be added up.

The basic idea is simple. Direct emissions come from sources the company owns or controls. Indirect emissions are caused by the company's activities but happen at sources someone else owns. The Scope 3 Standard (2011) says the three scopes are mutually exclusive for one company, so the same tonne is never counted twice inside one company's inventory.