The impact of Parallel Computing Infrastructures (PCI) on energy consumption and CO2 emissions worldwide can no longer be ignored. So far, most actions taken have focused on energy efficiency of PCI's underlying hardware, direct reduction of CO2 emissions, or user policies targeted to optimize hardware usage and consequently ensure that most CO2 emissions are justified, thereby minimizing the impact of computer infrastructures on global warming. Here, we discuss a simple software implementation designed to ensure that CO2 emissions by PCI's take place on-demand, without requiring (large) group policy strategies to be implemented. Adoption of this simple software in two computer clusters with approximately 100 cores each has lead to the total estimated energy savings in one year equivalent to 5 tons in CO2 emissions.