We compare the heat released directly due to combustion of fossil fuels to the heat accumulated indirectly in the earth system due to the effect of greenhouse gases (GHGs) associated with the fuels. We differentiate between GHG emissions from the combustion products of fossil fuels and from the fuel cycle activities of extracting, processing, and transporting the fuels. We find that the direct release of heat from the combustion of fossil fuels is minor in relation to the indirect accumulation of heat due to radiative forcing. The quantity of indirect heat accumulated by GHGs continues to increase over time, as additional energy is accumulated in the earth system as long as the GHGs remain in the atmosphere. Fuel cycle emissions contribute significantly to total lifecycle GHG emissions and radiative forcing. (C) 2013 Elsevier Ltd. All rights reserved.