On a large scale, it's basic physics. The jet streams are driven by temperature gradient: warm air from equatorial regions flows to the cold poles, warming up t

On a large scale, it's basic physics. The jet streams are driven by temperature gradient: warm air from equatorial regions flows to the cold poles, warming up the regions inbetween. The planet is not heating up uniformly, poles are heating up more than the equatorial regions. This of course means that the temperature gradient between the hot and cold realms is not as steep as it was. Net result? Weaker jet streams. Now it appears that moving heat from the equator to the (northern) high latitudes was only a part of the equation in keeping these latitudes temperate. Confining the freezing polar vortex to the pole was another. I'm sure there are others, and the population at large is going to learn about them in some very instructive ways in the future.