What is it?

As the world begins to focus more on reducing greenhouse gas emissions, many companies are under increasing pressure to meet carbon emissions targets, but this can’t always be done right away.

When a company can’t meet emissions targets, it may purchase what are known as carbon offset credits to go toward actions that reduce emissions or store carbon elsewhere. An offset credit is a transferrable instrument that represents one metric ton of carbon dioxide removed from the atmosphere. Companies can also sell credits when emissions are under the target amount.

But, not every action to reduce or store carbon is created equal, and some are more impactful. To measure the quality of a carbon offset, scientists look at the concept of additionality.

Additionality is the amount of “extra good” produced by a carbon-reducing or storage activity relative to the good produced without that activity, or the baseline.

An activity is deemed additional if it leads to lower emission levels, meaning the actual prevailing scenario is determined to have lower emissions than the baseline one.

Why it matters.

Additionality is a common tool used in carbon markets. A reduction in greenhouse gases is only considered additional if it would not have occurred in the absence of the opportunity to sell carbon offset credits. This means the sale of credits served as an incentive for more climate-friendly choices.

For example, say a company chooses to implement a certain technology in their production phase that reduces their carbon output. This company hopes to sell the offset credits they would have otherwise used up without that technology. These credits would be deemed additional and created quality credits that actually helped to reduce greenhouse gas emissions.

If the greenhouse gas reduction associated with an activity or project is not considered additional, then purchasing offset credits instead of reducing one’s own emissions won’t make a difference in reducing overall emissions. This means that understanding and measuring additionality is essential for offering effective carbon offset credits.

Want to learn more?

Read more about carbon credits and additionality in the Carbon Offset Guide and other works from the Greenhouse Gas Management Institute and Stockholm Environment Institute.