To heat something does require a transfer of heat energy from some source to whatever is heated. (realclimate.org)
Such a change will accelerate the flow of heat energy from the ocean surface to the atmosphere and offset any warming of the «skin» from any extra CO2 caused by humans. (newclimatemodel.com)
We use fossil fuels precisely because they have very high energy density — that is, they contain lots of heat energy in concentrated form; wind and solar do not. (austinchronicle.com)