Research article

Quantifying carbon emissions: Scope 1 (direct), 2 (indirect), and 3 (life-cycle)

National Physical Laboratory, Teddington, UK

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 7 July 2025
Accepted: 21 January 2026

Abstract

We analyse carbon emissions of Scopes 1, 2, 3 and discuss several case studies to illustrate direct and indirect emissions using state-of-the art measurement science. Direct emissions (Scope 1) can be measured and modelled at the moment when they are created in the field, taking into account instrumental errors and uncertainties; indirect emissions (Scope 2) require complex modelling and quantification of uncertainties because of heterogeneous energy systems, incomplete information and lack of direct measurements in remote locations; value chain emissions (Scope 3) include estimates produced by the supply chain of the products whose total (direct, real-time indirect, and life-cycle) emissions are being estimated. As such, Scope 3 emissions represent the biggest challenge for modelling and uncertainty quantification, because some information may be missing temporarily (reducible errors) or inaccessible in principle (irreducible errors). Our study proposes a systematic approach to studying and reporting carbon emissions of the three scopes and offers a novel case study on Scope 2 emissions.