Climate4you update May 2011

[Sunsettommy]

Climate4you

24 June 2011

Ole Humlum,Professor of Physical Geography, Department of Physical Geography, Institute of Geosciences, University of Oslo, Norway

SELECTED EXCERPT:

Comments to the May 2011 global surface air temperature overview
General: This newsletter contains graphs showing a selection of key meteorological variables for May 2011. All temperatures are given in degrees Celsius.

In the above maps showing the geographical pattern of surface air temperatures, the period 1998-2006 is used as reference period. The reason for comparing with this recent period instead of the official WMO ‘normal’ period 1961-1990, is that the latter period is affected by the relatively cold period 1945-1980. Almost any comparison with such a low average value will therefore appear as high or warm, and it will be difficult to decide if modern surface air temperatures are increasing or decreasing. Comparing with a more recent period overcomes this problem. In addition to this consideration, the recent temperature development suggests that the time window 1998-2006 may roughly represent a global temperature peak. If so, negative temperature anomalies will gradually become more and more widespread as time goes on. However, if positive anomalies instead gradually become more widespread, this reference period only represented a temperature plateau.

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