By Michael Mann & Phil Jones (guest)
Svalbard, an Arctic island in the Northern North Atlantic, is predicted to warm considerably more than most of the rest of the earth in many model-based scenarios. See for example the figure to the right, which represents a relatively high-end IPCC Third Assessment Report scenario for the projected surface temperature difference between the period 2071 -2100 and 1961-1990. Svalbard is the island north of Norway at about 80N between 15-30E.
The enhanced warming in this region is related to the issue of polar amplification that we have discussed previously on RC. It also happens that the Svalbard meteorological station is the 2nd station in the World Meteorological Organization (WMO) meteorological station list. This means that it tends to get noticed. The Climatic Research Unit (CRU) of the University of East Anglia maintains one prominent version of the global surface temperature data set and as part of its routine quality control, CRU flags any unusual (anomalous warm or cold) new measurements that come in. Svalbard has now been flagged consistently over the past several months, but the values have been confirmed as accurate by the Norwegian Met Service, which operates the Svalbard station.
Here are the recent Svalbard monthly surface temperature measurements, the long-term (1961-1990) means (“ybar”) and standard deviations (“sd”), and associated anomalies i.e., departure from average (“delta”) for Dec 2005 through April 2006 (all in degrees C):
Month Value ybar sd Delta Dec 05 -3.8 -13.3 4.4 +9.5 Jan 06 -2.7 -15.3 4.7 +12.6 Feb 06 -9.8 -16.3 3.7 +6.5 Mar 06 -13.1 -15.8 3.7 +2.7 Apr 06 0.0 -12.4 2.7 +12.4
The numbers are fairly remarkable. April’06 was warmer than any previously recorded May, and January ’06 was warmer than any previously recorded April. The previously warmest April was
-7.0C (1996) -4.3C (2004). There is currently an absence of sea ice off much of the coast of Svalbard, which is also unprecedented for so early in the year.
The April mean temperature is almost 5 standard deviations above the mean, a “5 sigma event” in statistical parlance. Under the assumption of stationary ‘normal’ statistics, such an event is considered astronomically improbable (< 1 in 106), and, like the summer heat wave in Europe in 2003 (which was a 5 sigma event in Switzerland, 3 sigma over Europe as a whole), deserves special attention. As we have nonetheless remarked before on RC, particular events, even seasonally-persistent anomalies as unusual as these, do not “prove” anthropogenic warming. But in a statistical sense, large outliers like this make it more probable that the underlying distributions are shifting and give us a glimpse into the types of anomalies we might expect to become more common in the decades ahead.
Correction and update: (1 June) Micheal Shouler points out that we misread the previous April record (corrected above). And now that the May 06 data has come in at a record-breaking +0.9 C, our statement that April 06 was warmer than all previously recorded Mays is still true – but only just! Things move fast in this field…