C

Carbon budget

The total amount of CO2 the world can still emit while keeping warming below a chosen limit, such as 1.5°C or 2°C. The IPCC Sixth Assessment Report (AR6, 2021-2023) estimates these budgets, and every year of high emissions uses up part of what is left.

Carbon credit

A tradable certificate that usually represents 1 tonne of CO2e reduced, avoided or removed by a project, after it has been checked under a set of rules. Credits are issued by a programme or registry, such as Verra, Gold Standard or India's CCTS, and are "retired" when someone uses them for a claim.

Carbon dioxide removal (CDR)

Human activities that take CO2 out of the atmosphere and store it for a long time, in trees, soils, rocks, the ocean or products. The IPCC AR6 glossary (2022) counts only deliberate human action as CDR, not natural uptake that would happen anyway.

Carbon footprint

The total greenhouse gas emissions caused by a person, product, event or organisation, expressed in tonnes of CO2e. It is an estimate, and the result depends on the boundary chosen and the emission factors used.

Carbon intensity

Emissions per unit of something: per rupee of GDP, per tonne of steel, per unit of electricity or per product. A company or country can lower its carbon intensity while its total emissions still rise, if output grows faster.

Carbon neutral

A claim that the emissions of a product, event or organisation have been measured, reduced and the rest balanced with credits or removals over a set period. ISO 14068:2026, which in September 2026 replaced ISO 14068-1:2023 with the same content under a new number, sets out how such a claim should be made and backed up.

CBAM (Carbon Border Adjustment Mechanism)

An EU law, Regulation (EU) 2023/956, that puts a carbon price on certain imports, such as iron and steel, aluminium, cement, fertilisers, hydrogen and electricity. A reporting-only phase ran from 1 October 2023 to 31 December 2025, and the definitive phase began on 1 January 2026, which matters for Indian exporters of these goods. A 2025 amendment, Regulation (EU) 2025/2083, exempts EU importers bringing in 50 tonnes or less of CBAM goods a year, and CBAM certificates go on sale from 1 February 2027.

CCTS (Carbon Credit Trading Scheme)

India's carbon market framework, notified by the Ministry of Power under the Energy Conservation Act, 2001 (as amended in 2022) on 28 June 2023 (S.O. 2825(E)) and amended in December 2023. It has a compliance mechanism, where covered industries must meet emission-intensity targets, and an offset mechanism, where other entities can register projects; the Bureau of Energy Efficiency (BEE) runs it.

CO2e (carbon dioxide equivalent)

A common unit that converts different greenhouse gases into the amount of CO2 that would cause the same warming over a chosen time, usually 100 years. It lets you add methane, nitrous oxide and other gases into one number.

Compliance market

A carbon market created by law, where certain companies must hold enough permits or credits to cover their emissions or meet targets. The EU Emissions Trading System and India's CCTS compliance mechanism are examples.

Corresponding adjustment

An accounting step under Article 6 of the Paris Agreement. When a country lets a credit be used by another country or for an international purpose, it adds that amount back to its own emissions total, so the same tonne is not counted twice.