The classic line of argument against any activity aimed at predicting, mitigating or adapting to climate change - It incurs emissions. We've seen this before with Al Gore, who flew around the world converting people to his inconvenient truth and with Bono, who'd done the same but with sunglasses on. Of course a supercomputer emits lots of C02, even a not so-super computer does that. Is it better to understand likely climatic change or not buy such a computer at all and stumble blindly towards a future we haven't planned for? I don't know, but my computer emits C02 and I'd like to think that over the course of its lifetime, it will contribute to policy making and decision making that results in far larger savings of C02.