In this study we used an improved approach to test the EKC hypothesis for carbon dioxide emissions by taking the first-order derivative of the traditional quadratic EKC equation. We found the long-term historical carbon dioxide emissions rarely supported the EKC theory at various scales (country to globe), but the short-term (especially the most recent decades) carbon dioxide emissions widely supported the EKC hypothesis. We concluded that though the overall development of a country or region might not follow an EKC pattern, but the EKC hypothesis might still be justified during different periods of the economic growth.