Has carbon-related and net zero terminology got you a little confused? You’re not alone. This handy guide clears up the key concepts used to discuss carbon and climate change.

Carbon is incredibly versatile, forming more compounds than all the other elements combined. It occurs in all living organisms and is the sixth most common element on Earth. Carbon plays an essential part in everything from coal to graphite to diamonds to fizzy drinks.

As a fundamental building block of life, carbon has many natural forms. There’s carbon dioxide gas, or carbon combined with hydrogen to form methane gas, and the hydrocarbons in crude oil. By mass, roughly 18.5% of our body is made from carbon, second only to oxygen.

Human activity, like burning fossil fuels, releases additional carbon. This combines with oxygen in the atmosphere to produce the greenhouse gas (GHG) carbon dioxide.

‘Carbon’ is widely used as a shorthand for carbon dioxide.

A glossary of net zero and carbon-related terms

Carbon neutral: Carbon neutrality means that, after taking action to reduce greenhouse gas (GHG) emissions, any remaining GHG emissions are ‘offset’ – or removed from the atmosphere – by an equivalent amount of carbon. Carbon neutrality can be claimed while companies are still on a pathway to net zero (and have started reducing carbon emissions).

Net zero: Net-zero carbon means reducing greenhouse gas emissions across an organization’s value chain, with the goal of balancing the emissions produced and emissions removed from the earth’s atmosphere.

Carbon offsetting: A practice in which carbon emissions are balanced by reduction in emissions elsewhere, usually through paying a third party (by purchasing carbon credits) to make emission reductions or sequester carbon. For example, emissions might be offset by investing in additional renewable energy sources or forestry projects, often in developing countries.

Carbon capture (also known as Carbon Capture, Utilization and Storage or CCUS): This is the process of capturing and dealing with carbon dioxide before it would otherwise be released into the atmosphere. For example, a power plant could capture its CO2 rather than releasing it. The carbon dioxide may be compressed into a liquid state and transported to a site where it can be pumped underground for storage. As an alternative to storage, CO2 can be used as a feedstock in a range of useful products and services. The UK government has announced an investment of up to £21.7 billion in the country’s first carbon capture and storage projects.

Carbon budget: A carbon budget sets a cap on the amount of carbon that can be emitted in a given timeframe by a country or company. The UK introduced a system of national carbon budgets within the 2008 Climate Change Act, putting a figure on the maximum level of carbon emissions permitted if reduction targets are to be met. The UK is currently pursuing the fourth carbon budget , which commits to a 51% reduction below 1991 levels by 2025. The budget extends to the sixth period (2033-2037) at which point emissions will need to be 78% below 1990 levels.

Carbon trading: Carbon trading is the buying and selling of rights that permit a company or other entity to emit a certain amount of carbon dioxide. Those carbon rights and the carbon trade are authorized by governments with the goal of gradually reducing overall carbon emissions and mitigating their contribution to climate change. Carbon trading is also referred to as carbon emissions trading.

Carbon pricing: A payment level applied to carbon emissions to incentivize reductions in emissions. This might be charged as a tax or through an auctioned permit system.

Carbon intensity: The amount of carbon emissions per-action. For example, the carbon intensity of electricity would be calculated by the number of grams of CO2 released to the atmosphere when a unit of electricity is generated. Or the carbon emissions resulting from a passenger travelling one kilometre.

Carbon accounting: The process of measuring how much CO2 (or equivalent) an organisation emits. The Greenhouse Gas Protocol is the most widely used accounting standard. BS EN ISO 14064-1 is the most widely adopted GHG quantification standard.

Carbon financing: Carbon financing provides funding for emissions-reducing projects and/or sustainable energy projects. Funding mechanisms put a monetary value on carbon emissions to, for example, allow companies looking to offset emissions by purchasing carbon credits.

Carbon negative: Sometimes referred to as ‘climate negative’ (or even ‘climate positive’). The net result of an organization’s initiatives decreasing the total volume of carbon in the atmosphere. This can be thought of as going one step further than carbon neutral.

Carbon removal: Taking carbon from the atmosphere and storing in a ‘carbon sink’ so that it can’t contribute to climate change. Sometimes known as carbon sequestration or carbon storage.

Greenwashing: Providing false or misleading information about an organization’s sustainability efforts when trying to promote environmental credentials. Greenwashing doesn’t have to be intentional, and sometimes happens because an organization isn’t taking scope 3 emissions into account when undertaking carbon accounting.

Scope 1, 2, and 3 emissions: ‘Scopes’ are part of the basis for required greenhouse gas reporting in the UK. They include:

• Scope 1 - GHG emissions that a company makes directly. For example, its vehicle emissions or emissions associated with heating gas boilers. Sometimes known as ‘direct emissions.

• Scope 2 - Indirect emissions that are purchased but not combusted onsite. In practice this means electricity, and less commonly, imported heat, steam, or compressed air.

• Scope 3Emissions a company is indirectly responsible for in its value chain. For example, emissions associated with the products it buys from suppliers, or emissions that occur after a company has sold its goods or services. Sometimes these are referred to as upstream or downstream emissions.

Standards that can help your organization achieve net zero

The reduction of carbon emissions starts with measurement, and there is no reliable system of measurement without standardization. 

Standards play a vital role in assisting organizations to first record and verify their emissions, and then to go on to plan and execute a credible and successful net zero transition.

Important net zero standards include: 

• BS EN ISO 14064-1:2019 Greenhouse gases - Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals

• BS EN ISO 14064-2:2019 Greenhouse gases - Specification with guidance at the project level for quantification, monitoring and reporting of greenhouse gas emission reductions or removal enhancements

• PAS 2060:2014 Specification for the demonstration of carbon neutrality

• BS 8001:2017 Framework for implementing the principles of the circular economy in organizations. Guide

• BS EN ISO 50001:2018+A1:2024 Energy management systems. Requirements with guidance for use

• BS EN ISO 14067:2018 Greenhouse gases. Carbon footprint of products. Requirements and guidelines for quantification

• BS EN ISO 14091:2021 Adaptation to climate change. Guidelines on vulnerability, impacts and risk assessment

• BS ISO 14068-1:2023 Climate change management. Transition to net zero - Carbon neutrality

• PAS 2080:2023 Carbon management in buildings and infrastructure

Learn more about how standards are supporting organizations to reduce their carbon emissions by visiting our Net Zero topic page.

Discover more about BSI Membership

Become a BSI member and you’ll be joining 11,000+ organizations committed to making positive change through standards. You’ll get extra support in implementing standards via a team of research professionals and stay up to date with relevant changes to standards with a monthly spreadsheet. Your personalized Membership certificate and digital Membership badge will help your organization stand out from the competition too. And every member enjoys a 50% saving on British Standards and BSI Knowledge subscriptions, and up to 50% on other standards and subscriptions. Find out more about BSI Membership here.