Nog een overzicht van het Amerikaanse "cherry picking", waarbij metingen van een zeer groot deel van de weerstations uit de dataset werden verwijderd en wel bij voorkeur die uit landelijke omgevingen die een "koelende" trend aangeven...
Climategate: CRU Was But the Tip of the Iceberg
[1]
http://www.americanthinker.com/2010/01/climategate_cru_was_but_the_ti.html
American Thinker on CRU, GISS, and Climategate
[2]
http://wattsupwiththat.com/2010/01/22/american-thinker-on-cru-giss-and-climategate/
NOAA stands accused by the two researchers of strategically deleting cherry-picked, cooler-reporting weather observation stations from the temperature data it provides the world through its National Climatic Data Center (NCDC). D’Aleo explained to show host and Weather Channel founder John Coleman that while the Hadley Center in the U.K. has been the subject of recent scrutiny, “[w]e think NOAA is complicit, if not the real ground zero for the issue.”
quote]Perhaps the key point discovered by Smith was that by 1990, NOAA had deleted from its datasets all but 1,500 of the 6,000 thermometers in service around the globe.
Now, 75% represents quite a drop in sampling population, particularly considering that these stations provide the readings used to compile both the Global Historical Climatology Network (GHCN) and United States Historical Climatology Network (USHCN) datasets. These are the same datasets, incidentally, which serve as primary sources of temperature data not only for climate researchers and universities worldwide, but also for the many international agencies using the data to create analytical temperature anomaly maps and charts.
Yet as disturbing as the number of dropped stations was, it is the nature of NOAA’s “selection bias” that Smith found infinitely more troubling.
It seems that stations placed in historically cooler, rural areas of higher latitude and elevation were scrapped from the data series in favor of more urban locales at lower latitudes and elevations. Consequently, post-1990 readings have been biased to the warm side not only by selective geographic location, but also by the anthropogenic heating influence of a phenomenon known as the Urban Heat Island Effect (UHI). [/quote]