Global warming?

According to the IPCC "hockeystick", the air temperature at observation height has increased about 1 degree during the past 100 year. This is by many people considered the proof of global warming. However many measuring stations are in a civilized environment and temperature may have been affected over the years by desiccation due to paving of the surface,  drainage of fields and lowering of groundwater tables. 

We have tried to verify the postulated global warming by means of Meteosat/MSG derived surface and air temperatures. We have also extracted global radiation. An area southwest of Tamanrasset in the Sahara has been chosen. Here greenhouse radiative forcing should be well expressed in the surface temperature whereas: (a) the area is natural and has no vegetation, (b) there are no CO₂ sinks and (c) there is no evaporation.

The graph above shows almost 30 year of Meteosat based surface temperatures (red), boundary layer temperatures (light blue), 2m-air temperatures (dark blue) and global radiation (yellow). The linear trend in the data is also shown. These data do not point to global warming during the past 30 year, but rather to a slight temperature decrease.

Could this only be the case at this location in the Sahara? To answer this question we have investigated the spatial distribution of the phenomenon. The picture below shows the difference in average surface temperature during the period 2000-2009 and the period 1983-1992. The map shows that the observed cooling is not a local phenomenon, but is taking place all over the hemisphere. There are only a few spots, indicated in red color, where some warming has taken place, which is most likely due to changes in land surface conditions.

Average surface temperature difference between the 10 yearly periods 2000-2009 and 1983-1992. The map shows that almost everywhere in the Euro-African region the temperature has decreased. The white marker is the approximate location where the temperature graph at the top of this page has been extracted from the data base.

Surface temperature anomalies

The maps below show the temperature anomalies in 2001 and 2009 relative to the climatic mean. 2001 was relatively warm in NW-Africa and the Middle-East (red). Europe was relatively cool (green). In 2009 the situation was more or less reverse.  Temperatures in NW-Africa were below average, and were relatively high in the Horn of Africa, Eastern Europe and Kazachstan.

2001 - avg                                             2009 - avg