After six inches of snow fell in 18° temperatures in Central Park on Friday, by Monday morning New York City was warm and rainy at 55°. Temperatures will plummet down again to a high temperature of 14° during the day on Tuesday.

Across the country record low temperatures are rolling in due to the ‘polar vortex,’ a mass of frigid air that has drifted down from far northern latitudes and settled over the central states — chilling the midsection of the US to below zero, including -15° in Chicago.

But it’s the yo-yoing temperatures that stand out here in NYC. Aside from the wardrobe confusion, rapid freezing and thawing is a cause of much expensive infrastructure havoc, including manhole fires from road salt penetrating Con Ed cables underground, new potholes, downed power lines, and streets and sidewalks glazed in treacherous ice.

Behind this chaotic weather pattern may be a shift in the way fronts have typically traveled across the continent, once brought to us on the East Coast via the historically reliable jet stream. It turns out that the jet stream has been stuttering in recent years — perhaps as a result of the vanishing sea ice in the Arctic, which has reduced the convection that formerly powered the northern winds. Researcher Jennifer Francis of Rutgers University makes a remarkably clear explanation of the effect — take a moment to watch:

Meteorologist Eric Holthaus expands on Francis’s theory in an article in the Daily Beast, “Thank Global Warming for Freezing You Right Now”, and includes a reminder that the cold we have in the US is not shared around the globe — in fact, Australia has been setting records for high temperatures across the interior. We may have the cold, but Europe has had a warm December (h/t also to Andy Revkin at Dot Earth for the global perspective). Here’s what the world beyond our borders looked like in December, with much of it warmer than usual:

 

 

 

 

 

 

 

 

 

In fact, 2013 was the fourth warmest year on record, according to NOAA (with the warmest ever month of November).

In terms of what to expect in New York City in coming years, it seems that yo-yo like swings may be a new ‘normal,’ though climate in a period of rising emissions will not stay in any particular pattern indefinitely. Looking back, we really did have some strikingly warm days in ‘cold months’ of 2013. Just a few days before Christmas, it was 71° in Central Park (12/22/13). And at the beginning of the year, last January included a high of 61° (1/31/13). Drawing on deep memory; decades ago, Central Park had snow lingering for months, with kids sledding every day. Now a snowfall returns to bare earth usually within a week or so.

What is ‘normal,’ and who decides? For a child born in 2010, rapid jolts in temperature are already part of their young existence — to them, temperature swings will be familiar, and so will a much hotter New York. In that sense, maybe our infrastructure adjustments, in both cold and hot weather, are the most urgent practical form of resilience. And promoting the social ability of older folks to cope with continuous change, while hopefully, rapidly, reshaping our lives for much lower emissions. Just to keep from going off the deep end, where there is nothing familiar.

Andy Revkin looked at this kind of generational adjustment during a record heat spell in July of 2010, in pondering whether specific events made people more conscious of climate change:

“I asked [sociologist Robert] Brulle to weigh in afresh considering a slow shift toward more or hotter heat waves. His answer explains why the situation is worse than the image of a frog sitting in a pot. It’s more like a sequence of frog generations, each with a different sense of the normal temperature of water.”