If fighting artificial climate change is your only goal, then yes. The key word here being 'if'. Going back to a medieval state of living might be a good way to stop manmade global warming, but in doing so we leave ourselves wide open to longer-term threats, such as ice ages, diseases, meteors and so on. Developing clean energy sources is a safe way to go fowards; doing away with our modern technology completely is just a way of going backwards.