1. Rapid warming of the Arctic is diminishing the temperature gradient in the Northern Hemisphere, causing the jet stream to get lazy and loopy. A southward bound section of a loop is bringing cold air into the eastern US.
2. Rapid warming of the Arctic has influenced the Arctic Oscillation, a natural atmospheric cycle, to make the jet stream loopy.
3. The jet stream is being disrupted by the Gulf Stream pushing warmer water farther to the north than before.
4. Increased autumn snowfall in Siberia causes a strengthening of the Siberian high pressure system, weakening the polar vortex and creating a more loopy jet stream.
5. The Arctic has less influence on the climate than the tropics. All of the above are wrong.

Ahem. The climate (ocean-atmosphere system) is extremely complex and chaotic. "Choatic" means that slight changes in the system can lead to widely divergent results, the so-called "butterfly effect". There are a variety of theories vying to be the explanation of recent weather, and all have their weaknesses. Theory no. 1 suffers from the fact that the increase in the "waving" of the jet stream over the past few decades is disputed. Theory no. 2 needs a longer data record to show it has merit. Theory no. 3 also needs more substantiation. Theory no. 4 is disputed by some who say there really hasn't been an increase in autumn snowfall in Siberia. Theory no. 5 (not so much a theory but a point of view) is the traditional wisdom. One thing is common: climate change. But then, is the Arctic a major driver of Northern Hemisphere climate, or is it not? Time may tell.