In this study, the environmental Kuznets curve (EKC) hypothesis is examined
for 3 developed countries, which are Denmark, the United Kingdom, and Spain,
for the period between 1960 and 2014. The EKC hypothesis is examined under 2
nexuses which are GDP, CO2 and energy consumption, and GDP, CO2, energy
consumption and the square of GDP. Causal and long-term relationships
between GDP, CO2, and energy consumption are examined for these 3 developed
countries using the ARDL bounds test, the Toda and Yamamoto Granger
non-causality test, the VAR Granger Causality/Block Exogeneity Wald test,
and the Johansen cointegration test. Long-term relationships between GDP,
CO2, energy consumption, and the square of GDP are examined by the Johansen
cointegration test. The EKC hypothesis is not confirmed for Denmark, the
United Kingdom, and Spain, and the neutrality hypothesis is confirmed for
these 3 developed countries. Unidirectional causality running from energy
consumption to CO2 is found for Denmark, and unidirectional causality
running from CO2 to energy consumption is found for the United Kingdom.