A Longitudinal Study on the History of Energy Transition and Its Implications on Global Decarbonization

A longitudinal study on per capita CO(2 )emissions of 164 economies over four decades shows that there is an inverted U-shape relationship between per capita CO2 emissions and per capita gross domestic product (GDP), as proposed by the environmental Kuznets curve. In general, an economy goes through three stages of energy transition based on its per capita GDP. When an economy's per capita GDP is less than $7000, change in per capita CO2 emission exceeds or tracks the change in per capita GDP. When an economy's per capita GDP is between $7000 and $24,000, per capita CO2 emission either tracks or lags behind per capita GDP. When an economy's per capita GDP exceeds $25,000, its per capita CO2 emission is decoupled from per capita GDP and even decrease. Furthermore, the evolution of energy mix of an economy can be displayed in a ternary diagram, with coal, oil-and-gas, and renewable and nuclear energies (REN) at the apexes. Results show that an economy's energy mix generally follows the trend going from coal-dominated to oil-and-gas-dominated and then REN-dominated. However, the rate of change in energy mix is slow and is less than one percent point per year for many economies, and therefore, relying solely on REN to replace fossil fuels to achieve net zero by 2050 is impractical. Other options including carbon capture and storage will be needed. An energy mix index is introduced, which can be used to track an economy's progress toward replacing fossil fuels by REN for primary energy consumption.