CO₂ intensity, a key metric in the fight against climate change, measures the amount of carbon dioxide (CO₂) emitted per unit of another variable, such as energy produced, economic output, or a specific activity. It is a vital tool for evaluating the environmental impact of different processes and for monitoring the reduction of greenhouse gas emissions.   

The indicator is a relative measure, which means it doesn't just tell the total amount of CO₂ emissions but how efficiently something is being done in terms of carbon emissions. A lower CO₂ intensity indicates a more carbon-efficient process or activity. Various and specific units are used to measure CO₂ intensity. Common examples include "grams of CO₂ per kilowatt-hour of electricity generated" or "tons of CO₂ per million dollars of GDP".  

Source: IEA "CO₂ emissions intensity of GDP, 1990-2021"

Historically, economic growth has often been coupled with rising CO₂ emissions. The debate surrounding carbon intensity suggests fairness and responsibility issues of allocating responsibility for emissions reductions fairly. Should developed countries, with historically high emissions, bear a more significant burden than developing countries? Should emissions be allocated based on consumption or production? This issue has long been a debate on climate change. 

While carbon intensity provides valuable insights, it is not a standalone solution. The importance of absolute emissions reduction cannot be overstated, underscoring the need for a comprehensive approach to addressing climate change.