Consider climate change, brutal winter in Europe, mild winter in US, and another early and severe start to the US tornado season. Are they connected? Well, the last three are, and a plausibility argument can be made for the first, but the connection is hardly iron clad.
The same positioning of the Polar vortex that brought a brutal winter to Europe made the US winter surprisingly mild, and it too contributed to the abnormal jet stream that promoted the tornadoes. The unusually mild winter also meant the US Midwest lacked snow cover at a time of year when it usually does, and that in turn meant sharper temperature differentials across the front that spawned the tornadoes.
So does climate change play a role? Maybe so. Here the logic seems to be that the unusually low surface ice extent in the Arctic means more evaporation and more Asian snowfall which affects the strength and positioning of the Polar vortex. Let's call that one TBD.