How to support economic development and improve the quality of the environment? This is the major issue that has brought together the various states at the 26th Conference of the Parties on Climate Change (COP26), which continue to reflect on how to further reduce greenhouse gas emissions.This book focuses on the question of the causal link between the level of greenhouse gas emissions and variables relating to dimensions of economic development (financial development, trade openness, economic growth) of ECOWAS countries compared to those of the EU over the period 1980 to 2018. To do so, we conduct short- and long-run Granger causality tests in a panel data vector error correction model (P-VECM). Our results mainly indicate that for both groups of countries trade openness is caused by financial development, economic growth and CO2 emissions.