As part of my Master and PhD theses I have used a lot of computer time on supercomputers in Jülich, Stuttgart, Bologna and the cluster in Bonn. I want to estimate the magnitude of CO₂ that this has released.
It is a bit hard to say how many core hours I have used exactly as I have already used data that existed already. Let's take like 5 Mh to pick a number. Then on JUWELS with the dual Intel Xeon Platinum 8168 with 48 cores that is around 100 kh. Each of the CPUs has a TDP of 205 W. Then there is network, file system, backup. Perhaps 750 W per node? And then there is cooling, which roughly takes the same on top, so 1.5 kW per node. That makes 150 MWh of electricity used. In Germany it seems that we would have to take 0.4 kg/kWh of CO₂. This would then give a little over 60 t of CO₂.