Inspired by Acheampong & Boateng (2019), nine variables that may have impacts on China's CO2 emissions are chosen as independent variables, as shown in Table 1. Raw data of these 10 time series, i.e. nine independent variables as well as CO2 emissions, are in annual form ranging from 1985 to 2020. To develop accurate models, the Chow–Lin method (Chow & Lin 1971) is used to convert the annual data into their corresponding quarterly versions, obtaining 144 quarterly samples for each variable. The sum of every four quarterly samples equals the raw annual observation. Hence, the quarterly data ranging from 1985Q1 to 2020Q4 are applied for this study. Each variable X is min–max normalized as below:
(1)
Table 1
Explanations and sources of nine independent variables as well as CO2 emissions
| Variable names | Variable explanations and units | Data sources |
|---|---|---|
| CO2 emissions | Total production-based emissions of carbon dioxide, including fossil fuels and cement production, excluding land-use change. (million tons) | Global Carbon Projecta |
| Foreign direct investment | The net inflows of investment to acquire a lasting management interest in an enterprise operating in an economy other than that of the investor. This series shows net inflows (new investment inflows less disinvestment) from foreign investors and is divided by GDP (%). | The World Bankb |
| Industry, value added | An increase in industrial activity. It comprises value added in mining, manufacturing, construction, electricity, water, and gas, and is divided by GDP (%). | The World Bank |
| Trade | The sum of exports and imports of goods and services measured as a share of GDP (%). | The World Bank |
| Urban population | Proportion of urban population to total population (%). | The World Bank |
| GDP per capita | Gross domestic product is divided by total population (current US$). | The World Bank |
| Energy consumption | Total energy consumption, including coal, oil, nature gas, and primary electricity and other energy sources. (10,000 tons of standard coal). | China Statistical Yearbookc |
| Coal | Proportion of coal consumption to total energy consumption (%). | China Statistical Yearbook |
| Oil | Proportion of oil consumption to total energy consumption (%). | China Statistical Yearbook |
| Gas | Proportion of nature gas consumption to total energy consumption (%). | China Statistical Yearbook |
| Variable names | Variable explanations and units | Data sources |
|---|---|---|
| CO2 emissions | Total production-based emissions of carbon dioxide, including fossil fuels and cement production, excluding land-use change. (million tons) | Global Carbon Projecta |
| Foreign direct investment | The net inflows of investment to acquire a lasting management interest in an enterprise operating in an economy other than that of the investor. This series shows net inflows (new investment inflows less disinvestment) from foreign investors and is divided by GDP (%). | The World Bankb |
| Industry, value added | An increase in industrial activity. It comprises value added in mining, manufacturing, construction, electricity, water, and gas, and is divided by GDP (%). | The World Bank |
| Trade | The sum of exports and imports of goods and services measured as a share of GDP (%). | The World Bank |
| Urban population | Proportion of urban population to total population (%). | The World Bank |
| GDP per capita | Gross domestic product is divided by total population (current US$). | The World Bank |
| Energy consumption | Total energy consumption, including coal, oil, nature gas, and primary electricity and other energy sources. (10,000 tons of standard coal). | China Statistical Yearbookc |
| Coal | Proportion of coal consumption to total energy consumption (%). | China Statistical Yearbook |
| Oil | Proportion of oil consumption to total energy consumption (%). | China Statistical Yearbook |
| Gas | Proportion of nature gas consumption to total energy consumption (%). | China Statistical Yearbook |
The unit of each variable is marked in parentheses.