U-V-W

Urban Heat Island (UHI): City heat in global temperatures

Posted by Frank Lansner (frank) on 9th February, 2010
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 ”UHI” = Urban Heat Island.

How much of the measured ”global warming” is due to the fact, that most land based thermometers is placed in or in the near surroundings of the growing cities?? This is obviously one of the central issues in the climate debate.

 

Cities are several degrees warmer than their surroundings (larger cities typically approx. 3 Celsius varmer than the surrounding nature) and bigger cities are warmer than smaller cities. Temperatures measured from the worlds stronlgy expanding cities therefore shows warming trend that is not related to the surface of the earth in general. Therefore it is a problem to measure ”globale temperatures” from cities of all places. But this is what GISS, NOAA and CRU mainly does.

 

Above, left: Houston city heat. The official temperature measuring station – the green spot – is today heated by the city. Above, right: here an illustration of how California temperature stations mostly shows warming trend in cities.

UHI mostly leads to warmer night temperatures, buildings, asfalt and concrete holds heat from daytime into night hours. Here visualized by heat sensitive illustration from Bucharest, Romania:

The whole UHI-discussion – which seems to annoy some – could easily have been avoided. NOAA/GHCN has reduced the number of temperature stationer outside USA to a only one third:

 

Due to the critical UHI issue it would be scientifically correct then to systematically omit the city thermometers. But this very day GISS, NOAA, CRU specifically chooses still to measure “global temperatures” mainly from cities. By doing so, GISS, NOAA and CRU themselves actively makes sure that the UHI debate continues.

 

Besides warm errors due to the still warmier cities, we also have serious issues concerning wrong sitings for temperature stations. This category of warm errors comprises: Too close to building, black asfalt, warm air ventilation outlets etcetc. Anthony Watts has systematically investigated the American temperature stations and found that 69% of all stations has severe errors and thus belongs to the 2 worst categories ”4” og ”5”. This rating is indeed based on the official demands for wheather stations. Practically all errors in placement leads to warmer trend in temperature. The relevant authorities NOAA has been notified with this “extern audit” long ago, but NOAA are not showing any willingness to correct their equipment. Stunning to witness, this apparent lack of will to achieve more correct temperatures. And stunning that NOAA themselves has not taken over this auditing job. It seems that errors has to be pointed out be people outside NOAA.

Check out: http://www.surfacestations.org/

 

 

Last changed: 28th February, 2010 at 02:19:02

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