If not handled properly, bitcoin mining is likely to affect the global use of resources and energy. The Bitcoin industry can not ignore the possible economic, social and environmental impact of cryptocurrencies.
I've already been extremely concerned about energy usage when it comes to Bitcoin mining. I don't think it is the most wasteful thing we've come up with as humans, but it certainly is up there with the amount of energy we use to accomplish our goals. The Bitcoin industry actually might be able to ignore all of the economic, social and environment impacts of POW mining for a long-time, because in a free market it will continue to grow until something better comes along or there are no longer the resources to sustain it. The economic system of the future would probably hold out a lot longer than almost anything else in terms of energy preservation and prioritization.
I'm really not 100% sure, but yea I do think it will only be a temporary halt. What I think is though, that EMP can actually destroy electronic hardware, not just sort of crash/stop them like when a blackout occurs. Though it's probably unlikely for an EMP to destroy 100% of the harddrives of the whole world. 
EMP interference is generally disruptive or damaging to electronic equipment, and at higher energy levels a powerful EMP event such as a lightning strike can damage physical objects such as buildings and aircraft structures. -Wikipedia
EMP interference is generally disruptive or damaging to electronic equipment, and at higher energy levels a powerful EMP event such as a lightning strike can damage physical objects such as buildings and aircraft structures. -Wikipedia
It sounds like paper wallets are our best defense against the dark arts. A really powerful EMP sounds like it would still only wipe out about 90% or so of the Bitcoin supply, even if it took out every hard-drive with it. This would serve to make Bitcoins extremely valuable once they come back online, or render them obsolete; again though, I believe there will be nodes so long as there is internet, so obsoletion would have to come to the internet first.