Record Warm December!
2006 Second Warmest Year on Record!
December and Annual 2006 Climate Summary

Dr. David A. Robinson
New Jersey State Climatologist
Center for Environmental Prediction, Cook College/NJAES, Rutgers University

January 4, 2007

For the second consecutive month, the New Jersey-wide temperature was the warmest on record (dating back to 1895). December's 42.1° was 6.7° above average, surpassing the previous warmest 41.7° in 2001. Precipitation in December totaled 2.20" which is 1.50" below average. For the year, precipitation across the Garden State averaged 52.06", which is 4.86" above average. This makes 2006 the 15th wettest year of the past 112.

The "blazing" two-month end of 2006 resulted in it being the second warmest in NJ (55.3°, or 2.6° above normal). Only 1998, at 55.6°, was warmer. In fact, 8 of the 12 warmest years have occurred since 1990 (see table)


The warmth of the past few months is a result of the polar jet stream, which serves as the boundary between polar air to the north and milder air to the south, staying north of the region more often than usual. Thus NJ has been under the influence of air that has traveled from the Pacific directly across the nation, or has arrived in our region from the south. With few exceptions, polar air has not invaded these parts since the beginning of November.

Why the jet stream has behaved as such is a more difficult question to answer.  It is likely the result of a combination of several factors, including, 1) a weak to moderate El Nino event occurring in the tropical Pacific, with resultant impacts on global circulation; 2) a pattern of sea surface temperature anomalies in the North Pacific and North Atlantic that interact with the overlying atmosphere and influence atmospheric circulation; 3) the below average extent of snow cover across North America, thus the absence of this "refrigerant" sitting at the base of the atmosphere; and 4) the lack of strong high pressure systems in the high latitudes serving to direct cold air toward the middle latitudes.  Some have stated that this warmth is all due to the El Nino.  This is simply not correct.

As to the warmth of the past year and past several we have to look toward human influences on our atmosphere and landscape.  Some call this global warming, others the greenhouse effect.  Whatever you name it, there is ever increasing evidence that regional to global warming is occurring in part due to human factors.  This human fingerprint is accompanied by natural variations that have always occurred and always will.  Thus, for instance, the warmth of the past two months would have occurred without humans inhabiting the planet.  However the warmth of late may have become the warmest for this time of the year in the past century due to the added influence of humans.  This is difficult or impossible to prove, but appears to be there underlying the natural day to day, month to month fluctuations.

Past Climate Summaries