Complex sentence: At times the assessments variably and sometimes inconsistently include the contribution from the energy source's facility decommissioning, that is, the global warming potential of the process to return the power supply site to greenfield status.
Split into simpler sentences: At times the assessments'variably, and sometimes inconsistently, include the contribution from the energy source's facility decommissioning. This includes the global warming potential of the process to return the power supply site to greenfield status.