A carbon border adjustment (CBA) is a trade-policy instrument that imposes a charge on imported goods reflecting the greenhouse-gas emissions generated during their production. The goal is twofold: to prevent carbon leakage — the relocation of emissions-intensive industries to jurisdictions with weaker climate rules — and to protect domestic producers who already pay for emissions under a carbon tax or emissions trading system (ETS) from being undercut by cheaper, higher-emission imports.
The mechanism typically works by calculating the embedded CO₂ in a tonne of imported steel, cement, aluminium, fertiliser, or electricity, then requiring importers to surrender certificates priced at the domestic carbon price, minus any carbon price already paid abroad. In principle this restores a level playing field and extends the reach of climate policy beyond a single jurisdiction.
The most developed example is the EU Carbon Border Adjustment Mechanism (CBAM), adopted in 2023 under Regulation (EU) 2023/956. It entered a transitional reporting-only phase on 1 October 2023 and is scheduled to begin financial obligations in 2026, initially covering iron and steel, cement, aluminium, fertilisers, electricity, and hydrogen. The CBAM is being phased in alongside the gradual removal of free EU ETS allowances for the same sectors.
CBAs are politically contested. Supporters argue they make ambitious climate policy domestically viable and incentivise cleaner production globally. Critics — including several developing-country exporters such as India, Brazil, and South Africa — argue that border adjustments shift climate costs onto poorer trading partners and may violate WTO non-discrimination principles (GATT Articles I and III), though defenders point to the Article XX environmental exceptions. Compatibility with the common but differentiated responsibilities principle of the UNFCCC is also disputed.
Beyond the EU, the United Kingdom has announced a CBAM for 2027, and similar proposals have been floated in Canada, Australia, and the United States, though none has yet been enacted at federal level in those jurisdictions.
Example
In October 2023 the European Union launched the transitional phase of its Carbon Border Adjustment Mechanism, requiring importers of steel, cement, aluminium, fertilisers, hydrogen, and electricity to report embedded emissions ahead of financial charges beginning in 2026.
Frequently asked questions
A tariff applies a flat or product-based duty, while a CBA varies with the verified greenhouse-gas emissions embedded in each shipment and is offset by any carbon price already paid in the country of origin.
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