The Return of Severe Cold to the New York City Metro Area

While most Lehman College students are off until the start of the spring 2014 semester, the opening week of January has seen the College closed on account of a snowstorm, along with two shots of severe cold that transformed the campus a great outdoor freezer.

Top Left: January 3 snowstorm that closed Lehman College; Top Right: Freezing rain on January 5; Bottom Left: Sunrise on January 7; Bottom Right: Ice at low tide on January 7.

An anonymous 16th Century writer once observed:

This winter’s weather it waxeth cold,
And frost it freezeth on every hill,
And Boreas blows his blast so bold
That all our cattle are like to spill.

Just last week on January 7, it truly did “waxeth cold.” Despite brilliant sunshine and deep blue skies, the thermometer could only reach 10° during the daytime (the daily maximum temperature was 19°, which occurred near midnight). Boreas’ frigid westerly to northwesterly blasts locked wind chill readings well below zero throughout the day.

Just how cold was it? Was this perhaps the kind of cold one’s parents or grandparents spoke about?

Not quite. Unaccustomed to severe cold in recent years, one might be forgiven for thinking that the kind of cold that gripped the region had not been seen for generations or longer. Media headlines concerning the southward journey of the Polar Vortex into the United States likely reinforced such thinking. To be sure, in some cities in the Great Lakes Region, Ohio Valley, and Middle Atlantic States, some temperatures were the coldest since 1994—a year when the Internet was still in its infancy, today’s ubiquitous tablets and smartphones did not exist, and the universe of electronic resources one can currently leverage on the Leonard Lief Library’s website had yet to be created—especially daily high temperatures.

New York City has seen colder temperatures. Even as some of Lehman’s students have never experienced a subzero temperature during their lifetimes, the City has had subzero days. The last such day occurred on January 19, 1994 when the temperature bottomed out at -2°. So, it has been colder in the past.

In context, the recent cold has produced the lowest temperature, most days with high temperatures below 20° and low temperatures below 10° in almost a decade.  The January 7 low temperature of 4° broke the daily record of 6°, which had been set way back in 1896. It was also New York City’s coldest temperature since the thermometer at Central Park registered 1° on January 16, 2004. The below chart shows the winter average temperature (December-February), number of days with maximum temperatures below 20°, the season’s lowest maximum temperature, number of days with minimum temperatures below 10°, and the season’s lowest minimum temperature for winters beginning with 2000-01:

In addition, even as some might be tempted to question climate change given the combination of the cold, blogosphere chatter, and jokes in the media, the recent cold shots do not provide any indication that climate change is not ongoing. It is.

Even as parts of North America shivered, temperatures on a global basis continued to run above normal. In fact, according to the GISS dataset, the last month with a below normal global temperature was February 1994 (0.01°C below normal). Moreover, when the data comes in this week, 2012 will likely have been the 6th warmest year on record according to the GISS dataset (land and ocean surface temperatures). In addition, overall oceanic heat content has continued to increase.

Instead, the cold is the result of a synoptic pattern that allowed for the Northern Hemisphere's coldest temperatures to move into North America and then later come southward. Those changing patterns occur within the context of oceanic cycles (e.g., El Niño Southern Oscillation) and changes in radiative forcing, both from natural factors (e.g., changes in solar activity) and anthropogenic ones (e.g., greenhouse gas emissions that have contributed to a rising atmospheric concentration of greenhouse gases). Hence, the recent severe cold does not present a valid argument against the scientific consensus on climate change and it does not undermine the growing body of evidence that sustains and strengthens scientific understanding of climate change, including the anthropogenic role.

In the meantime, a January Thaw is now underway, even if it is a bit early according to popular lore. Make the most of it. If recent history is any guide, it won't last. Since 1981, all five winters with at least one low temperature of 2 or more standard deviations below the average January minimum temperature (1981-2010 climate base period) during the first half of January, as was the case on January 7, had at least another shot of much colder than normal air, usually by late January or early February.





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