Scope 1, 2, and 3 are the three categories the Greenhouse Gas Protocol uses to sort a company’s greenhouse gas emissions. Scope 1 covers direct emissions from sources the company owns or controls, such as fuel burned in its boilers, furnaces, and vehicles. Scope 2 covers indirect emissions from the energy it buys, such as purchased electricity, steam, heat, or cooling; those emissions physically happen at the power plant but are counted by the company because they result from its energy use.
Scope 3 covers all other indirect emissions in the company’s value chain, both upstream (for example, from suppliers making the goods it buys) and downstream (for example, from customers using its products). Together, the three scopes make up a company’s full emissions inventory.
Source: GHG Protocol: Scope 3 Frequently Asked Questions; examples from U.S. EPA: Scope 1 and Scope 2 Inventory Guidance.
Image: Former Huntley Generating Station, Tonawanda, New York, by Ken Lund, CC BY-SA 2.0, via Wikimedia Commons.