Storms in the western US get headlines, but record highs in the East are the bigger puzzle. Is it global warming?
As they dig out from under thick snow dropped by back-to-back holiday blizzards, residents of Colorado, northern and central New Mexico, and several Plains states may wonder what the rest of winter holds for them. But at least the patterns behind such weather are predictable. They're typical of the long arm of El Niño, which now reigns in the tropical Pacific.
For residents of the East Coast – not to mention Europe – it's a different story. Record-setting warmth, which gave Muscovites near shirt-sleeve weather, has everyone scratching their heads. So far this season:
•Williamsport, Pa., saw a record high of 70 degrees F. last month and the least snow ever recorded for December.
•In Scotia, N.Y., wet-suited water skiers sped along the Mohawk River – one of their earliest appearances on record.
In Europe, it was more of the same:
•Vienna posted its mildest New Years Day in 155 years. The high reached 57 degrees.
•In mid-December, Muscovites strolled the Russian capital in 47-degree weather – a record wintertime high for the city. Even in frigid western Siberia, temperatures for the first 10 days of December ran six to eight degrees above normal.
Is global warming responsible? Researchers aren't sure. They point instead to a seesaw climate pattern that occurs over the North Atlantic, called the North Atlantic Oscillation or NAO. Less publicly known than El Niño, and certainly less understood, the NAO is getting increasing attention from scientists. Their goal is twofold: to develop useful forecasts of the oscillation and to better estimate whether global warming is exaggerating its effects.
Unlike El Niño, the phenomenon's reach isn't fully globe-circling. But particularly in the winter months, the NAO "is just as important for weather and climate across much of the northern hemisphere," says James Hurrell, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colo.