The different fuel types in the mix of electricity production have vastly different emissions of CO2 and so different contributions to global warming. Many detailed studies have been performed to estimate the CO2 equivalent emissions in the life-cycle of power plants, taking into account numerous factors ranging from construction to operation, as well as the emissions during fuel consumption. Because of the complexity of these studies different values exist for gCO2 equivalent/KWh of produced electricity.
The analyses on this website use values published by IPCC in 2014 as shown in the figure below.
The figure below indicates the range of values from different studies.
Here it can be seen that there is a large range of values between studies. In the plots which compare CO2 equivalent emissions between countries these differences would not influence any conclusions because the essential feature is the factor 50 difference between fossil fuel and renewables. With this it is the fraction of fossil fuel generation which really defines the polluting nations.