This thesis has investigated the validity of the Environmental Kuznets Curve in the provinces of China which assumes the increase in GDP per capita (income per capita) would generate the raise of CO2 emissions (pollution) until a turning point in which CO2 emissions start decreasing. The study includes 30 provinces over a period spanning from 2000 to 2019 by applying OLS and Fixed-effects regression model with panel data. The findings demonstrate that the provinces of China conform to the EKC theory's projections by exhibiting an inverted-U shape. Apart from that, this study also confirmed the presence of differences in turning points between provinces with high income and those with low income, and the former exhibiting a significantly higher value. Our research findings suggest that policymakers should tailor their CO2 emission reduction policies to the specific circumstances of each region. In the absence of appropriate measures, a negative outcome may arise.

The Intergovernmental Panel on Climate Change 2018 highlights the importance of short-lived greenhouse gasses to combat global warming. This study explores the relationship between Gross Domestic Product per capita and methane per capita. The relationship is explored in relation to the Environmental Kuznets Curve theory where the subjects to examination used are High Income Countries and Low Income Countries based on United Nation classifications in 2019. In total 47 countries are examined where 30 countries are High Income Countries and 17 are Low Income Countries. The relationships are examined for the time periods 1970 to 2017 through Fixed Effect Models. To improve accuracy additional control variables are added: Population in agriculture (% of total employment), balance of payments and forest areas. With the added control variables, the time frame used in Fixed Effect Models changes to 1991 to 2017. The different Fixed Effect Models provide inverted U-shaped relationships for Low Income Countries and uncertain results for High Income Countries according to the Environmental Kuznets Curve.