Tuesday, April 3, 2018

Another Warm Winter

For the fourth time in the past five years, the November-March mean temperature in Fairbanks was significantly warmer than the 1981-2010 average, i.e. the mean temperature was in the upper tercile of the 1981-2010 distribution.  Each calendar month was also warmer than normal, and in fact this warm "streak" goes back to last June; each of the past 10 calendar months has been at least 1°F warmer than normal.  This kind of persistent warmth is not unprecedented, but it's certainly unusual.

The chart below shows running annual mean temperatures (daily max/min/mean) in Fairbanks since the beginning of the NWS/Weather Bureau era.  The recent warmth has raised the annual mean to nearly 32°F, a threshold that was exceeded for part of 2016.

It's interesting to note that some very cold years in Fairbanks had annual daily maximum temperatures below freezing, but that hasn't happened for many years.  Also of note: the long-term trends in maximum and minimum temperatures are quite similar over the entire period, but minimum temperatures increased more dramatically in the climate shift of 1976-77.  Consequently, the linear trend in minimum temperatures since 1976 is actually negative (-0.15°F/decade), but daily maximum temperatures have continued to increase (+0.20°F/decade).  Of course we have to take these numbers with a grain of salt owing to location and instrumentation changes in the official climate record.

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