It can spike up when new miners join the game, possibly in remote locations of the world with defunct governments that decide that mining Bitcoin for a select few is a more "important" use of their non-clean energy source. The network will react, miners in other parts of the world where regulations do not allow the same may scale their operation down, but there was a spike, and much more importantly you now incentivized burning resources by whatever means available where regulations do not stand in the way.