Hot Winter Days

The anti-scientific M.O. of some political conservatives was in full swing during the ‘polar vortex,’ as frigid weather brought south from the Arctic led many commentators to scoff, “look how cold it is, can you believe anyone thinks the Earth is getting warmer?” Coby Beck adds some perspective from climate historian Christopher C. Burt on A Few Things Ill-Considered, writing “cold snaps like this past week’s used to occur every couple of years in the 1800′s,” and more like every 5-10 years in the 1900’s. Meanwhile the last time it got so cold in the U.S. was twenty years ago. Coby says “what is remarkable is that this level of cold has become remarkable”—because it used to be commonplace. As the planet gets warmer, regional weather, unlike average global temperature, remains highly variable. Coby concludes, “this is just what scientists refer to as ‘winter.'”  Or what they used to, anyway.

Greg Laden offers a complementary interpretation, saying the polar vortex is the result of a jet stream increasingly unsettled by the warming of the Arctic. Per the theory of “weather whiplash,” extreme temperatures might become more common as the energized jet stream contorts Arctic air. While the eastern U.S. was suffering bitter cold, northern Europe enjoyed unseasonal warmth; there’s only so much Arctic air to go around.  Which means the northern hemisphere can look forward to hot winter days as surely as very cold ones.  The polar vortex was entirely consistent with global warming, and those who claimed otherwise wore their disingenuity on their sleeves.


Cold, Hard Facts

Coldness can manifest where you least expect it: on a planet rapidly warmed by the combustion of fossil fuel, or in the heart of a star 250 times as massive as our own. On Greg Laden’s Blog, Greg explains that an apparent “recovery” of Arctic sea ice from its historic low in 2012 does not invalidate the long-term trend. Greg also explains this year’s legacy of extreme weather, such as snow in Cairo, writing that when there is less difference in temperature between equatorial and polar regions, “the jet streams get all wiggly and cause northerly air to reach far to the south in some places and southerly air to reach farther north in other places.” Meanwhile, on Starts With a Bang, Ethan Siegel explores the different fates awaiting stars of different sizes. When a star like our own runs out of fuel and begins to collapse, it blows off its outer layers and leaves behind a neutron star or small black hole. Bigger stars, however, start producing antimatter, which lowers the pressure in the star and generates gamma rays that heat up the core even further. These stars end in a pair-instability supernova, which “not only destroys the outer layers of the star, but the core as well, leaving absolutely nothing behind!” But in the biggest stars in the universe, gamma rays cause photodisintegration, which cools down the interior of the star and allows all its mass to collapse into a black hole. The earliest of these massive black holes probably seeded the centers of galaxies, which now contain millions of solar masses.