Carbon Offset / Carbon Credit
A carbon credit is a tradable certificate representing one metric tonne of CO2 equivalent avoided or removed from the atmosphere; a carbon offset is the project that generates the emission reduction.
Climate ScienceCarbon credits and offsets are market-based mechanisms designed to channel investment toward greenhouse gas reduction projects. The principle is that, for climate mitigation purposes, it does not matter where in the world an emission reduction occurs - the atmospheric effect is the same.
How They Work
A project developer implements a project that reduces or removes greenhouse gas emissions (e.g., building a wind farm or planting a forest). An independent third-party auditor verifies the emission reductions. A carbon crediting program (such as Verra’s Verified Carbon Standard or the Gold Standard) issues credits equal to the verified reductions - each representing one metric tonne of CO2 equivalent. A buyer purchases and “retires” the credits, permanently deactivating the serial number to prevent resale or double counting.
Two Types of Markets
- Compliance markets: Created and regulated by governments as part of mandatory emissions programs. The EU Emissions Trading System (EU ETS) is the world’s largest compliance carbon market, covering power generation, heavy industry, and aviation within Europe.
- Voluntary markets: Enable organizations and individuals to purchase credits beyond regulatory requirements, typically as part of net-zero commitments. Major voluntary standards include Verra (VCS), Gold Standard, American Carbon Registry, and Climate Action Reserve.
Quality Criteria
For a carbon credit to be credible, it must meet:
- Additionality: The reduction would not have occurred without carbon credit revenue
- Permanence: The reduction is long-lasting and not easily reversible
- No double counting: The same reduction is not claimed by more than one party
- Conservative baselines: Reductions are calculated against realistic assumptions
- Verification: Independent third-party auditing confirms reductions are real
Why It Matters
Carbon markets direct private capital toward climate solutions and provide flexibility for organizations to manage emissions cost-effectively. However, offsets can enable “greenwashing” by allowing organizations to claim progress without reducing their own emissions. The quality of credits varies significantly, and the market has faced scrutiny over projects that don’t deliver claimed reductions. As carbon accounting becomes more rigorous, understanding how credits work - and their limitations - is essential for sustainability professionals.