Greenhouse gas emissions are measured and reported using various methods. The GHG Protocol Corporate Standard classifies a company’s GHG emissions into three ‘scopes’. Scope 1 covers direct emissions from owned or controlled sources, Scope 2 covers indirect emissions from the generation of purchased energy, and Scope 3 includes all other indirect emissions that occur in a company’s value chain. Countries and organisations use ‘bottom-up’ approaches to estimate emissions, complemented by ‘top-down’ measurements from atmospheric observations.