A process for upgrading raw synthesis gas comprising at least CH4, CO2, CO and H2, includes heating the raw synthesis gas by addition of energy derived from electricity to provide an upgraded synthesis gas comprising less CH4 and CO2 and more CO and H2 than the raw synthesis gas. The invention extends to a process for producing synthesis gas, which process includes reforming a hydrocarbonaceous gas feedstock which includes CH4 to raw synthesis gas comprising at least CH4, CO2, CO and H2, and upgrading the raw synthesis gas in a process which includes heating the raw synthesis gas by addition of energy derived from electricity to provide an upgraded synthesis gas comprising less CH4 and CO2 and more CO and H2 than the raw synthesis gas.