Steve B, in the comments, points to an AP story about a new study in Science Friday by Fu et al. on what they say is evidence that the jet stream is creeping poleward. They only hint at the implications in the paper, noting that “the poleward shift of the jet streams and the associated subtropical dry zone, if it continues, could have important societal implications.” Umm, yeah, speaking as someone living on the margins of an area that would likely get drier, I would say that would be an understatement. But it’s a very short time series (1979-2005), so caution is in order.