The KAYA identity

The clock is ticking. We need to bend the greenhouse gas emissions curve by 2025 according to the Intergovernmental Panel on Climate Change (IPCC). But to be able to decrease emissions levels, individuals and in particular policymakers first need to understand what factors are contributing to said emissions. Luckily, the Kaya identity explains CO2 emissions as the product of population, gross domestic product per capita, energy intensity and carbon intensity.

By analyzing the factors of this identity, one can better comprehend the different options to reduce the overall levels of CO2 emissions. 

Population is defined by the number of human beings on Earth. It is expected to increase and to reach 9.8 billion in 2050. 

Gross Domestic Product (GDP) per capita is the average economic output by person. It is also expected to increase and according to the International Monetary Fund (IMF), the global GDP will grow by 2.9% in 2023 and by 3.1% in 2024. 

Many environmental activists argue that “infinite growth on a finite planet is impossible”. They thus advocate for degrowth. It would imply that the change in the GDP for capita would be negative. Following the Kaya identity, such negative change would indeed decrease the levels of CO2 emissions. On the other hand, numerous experts support that such contraction of the economy can be avoided by carrying out an “absolute decoupling” of the economic growth and emissions growth. An absolute decoupling is an event that “occurs when the relevant environmental pressure is stable or decreasing while the economic driving force is growing” according to the European Union Nomenclature.

But how could we achieve such decoupling? Well, we might be able to do so thanks to the last two factors of the equation. 

The energy intensity of our economy is the quantity of energy needed to produce one unit of GDP. To lower said energy intensity, one could aim to make buildings and durable goods more efficient in order to save up energy overtime. For instance, the insulation of buildings would contribute to such a goal. Another measure would be to transform our industrial processes and transportation systems thanks to energy-efficient technologies and modal shifts. Additionally, shifting to less energy-intensive industries would also be an approach. For example, the service sector is considerably less intensive than the manufacturing one as one can see in the following graph.

The carbon intensity of our energy is the quantity of CO2 released per unit of energy. 

In order to decrease it, one can reduce the share of fossil energy in the energy mix. 

This can be done by exploiting low-carbon energy sources like renewable or nuclear energies. On the other hand, it is also possible to decrease the carbon intensity of fossil energy by employing Carbon Capture and Storage (CCS) technologies or by switching coal for gas which is considered less dirty and emits less CO2.

Recent Trends

In recent years, the negative change in energy intensity and carbon intensity were not considerable enough to compensate for the positive growth in population and GDP per capita.

As a result, the total level of CO2 emissions is still increasing. 

The major limitation of the Kaya identity is that it only encompasses C02 emissions, and not other greenhouse gasses like methane which has 80 times the warming power of CO2 over a 20-year period.

Nevertheless, the Kaya Identity is a simple tool to grasp the different alternatives to reduce the levels of CO2 released into the atmosphere. In order to effectively cut down CO2 emissions, we need an accumulation of several if not all the aforementioned solutions and their large-scale deployment.

By Marie Goepfert














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