Your graphs don't show any evidence that the changes in latency are happening within Verizon's network.
I too see variations in latency to various servers in Europe but those variations are usually happening on the other side of the Atlantic where Verizon has no control.
You might try running PingPlotter, rather than the prgram you used to provide those graphs, to see where the delays are actually occurring.
And having said that, it amazes me that Internet connections across the Atlantic work as well as they do. I think we've become spoiled in expecting packets running under the ocean, and then through many servers on the other side, to be as reliable as turning on a light bulb in our home. Me, I've come to expect and accept some variation in perfomance.