Evaluating the Mutual Relationship between IPAT/Kaya Identity Index and ODIAC-Based GOSAT Fossil-Fuel CO2 Flux: Potential and Constraints in Utilizing Decomposed Variables

Abstract

The IPAT/Kaya identity is the most popular index used to analyze the driving forces of individual factors on CO₂ emissions. It represents the CO₂ emissions as a product of factors, such as the population, gross domestic product (GDP) per capita, energy intensity of the GDP, and carbon footprint of energy. In this study, we evaluated the mutual relationship of the factors of the IPAT/Kaya identity and their decomposed variables with the fossil-fuel CO₂ flux, as measured by the Greenhouse Gases Observing Satellite (GOSAT). We built two regression models to explain this flux; one using the IPAT/Kaya identity factors as the explanatory variables and the other one using their decomposed factors. The factors of the IPAT/Kaya identity have less explanatory power than their decomposed variables and comparably low correlation with the fossil-fuel CO₂ flux. However, the model using the decomposed variables shows significant multicollinearity. We performed a multivariate cluster analysis for further investigating the benefits of using the decomposed variables instead of the original factors. The results of the cluster analysis showed that except for the M factor, the IPAT/Kaya identity factors are inadequate for explaining the variations in the fossil-fuel CO₂ flux, whereas the decomposed variables produce reasonable clusters that can help identify the relevant drivers of this flux.

Keywords: CO2 flux; GOSAT; IPAT/Kaya identity; correlation; hierarchical cluster analysis.

Figure 1

Distribution map of country clusters on the basis of fossil-fuel CO₂ flux, Kaya identity (G and I factors), and decomposed variables of G and I factor (GDP, population, TEC). (a1) Country cluster with the fossil-fuel CO₂ flux and G factor. (a2) Country cluster with the fossil-fuel CO₂ flux and decomposed variables of G factor (GDP and population). (b1) Country cluster with the fossil-fuel CO₂ flux and I factor. (b2) Country cluster with the fossil-fuel CO₂ flux and decomposed variables of I factor (GDP and TEC).

Figure 2

Distribution map of country clusters on the basis of the fossil-fuel CO₂ flux, Kaya identity (M, E, and P factors), and decomposed variables of M, E, and P factors (EC, TEC, CO₂ emissions from fossil fuel, and population). (a1) Country cluster with the fossil-fuel CO₂ flux and M factor. (a2) Country cluster with the fossil-fuel CO₂ flux and decomposed variables of M factor (EC, and TEC). (b1) Country cluster with the fossil-fuel CO₂ flux and E factor. (b2) Country cluster with the fossil-fuel CO₂ flux and decomposed variables of E factor (CO₂ emissions from fossil fuel and EC). (c1) Country cluster with the fossil-fuel CO₂ flux and P factor. (c2) Country cluster with the fossil-fuel CO₂ flux and decomposed variables of P factor (population).