That is a complete load of crap from the whackos at WUWT who have no credibility at all. If they dropped 6,00 stations there would be no stations. Only DUPLICATE stations were eliminated because of Bush II budget cuts!!! Why don't you deniers fund the reopening of the duplicate sties???? Oh that's Right, you know they're duplicates and if you opened them you would only CONFIRM Hansen's data. Much better for deniers to make up lies.
BTW, they checked to see if there was a bias from poorly sited stations after you deniers whined about them and they found the bias was for mostly COOLER readings. So were deniers happy when the poorly sited stations were removed from the data sets? Hell no, they then condemned Hansen for correcting the data and posting adjusted charts with the poorly sited stations removed. NOAA make all this info freely available to all, including you deniers, but deniers prefer to ignore it.
The USHCN Version 2 Serial Monthly Dataset
Station siting and U.S. surface temperature trends
Recent photographic documentation of poor siting conditions at stations in the USHCN has led to questions regarding the reliability of surface temperature trends over the conterminous U.S. (CONUS). To evaluate the potential impact of poor siting/instrument exposure on CONUS temperatures, Menne et al. (2010) compared trends derived from poor and well-sited USHCN stations using both unadjusted and bias-adjusted data.
Results indicate that there is a mean bias associated with poor exposure sites relative to good exposure sites in the unadjusted USHCN version 2 data; however, this bias is consistent with previously documented changes associated with the widespread conversion to electronic sensors in the USHCN during the last 25 years (see e.g., Menne et al. 2009). Moreover, the sign of the bias is counterintuitive to photographic documentation of poor exposure because
associated instrument changes have led to an artificial negative (“cool”) bias in maximum temperatures and only a slight positive (“warm”) bias in minimum temperatures.
Adjustments applied to USHCN Version 2 data largely account for the impact of instrument and siting changes, although a small overall residual negative (“cool”) bias appears to remain in the adjusted USHCN version 2 CONUS average maximum temperature. Nevertheless, the adjusted USHCN CONUS temperatures are well aligned with recent measurements from the U.S. Climate Reference Network (USCRN). This network was designed with the highest standards for climate monitoring and has none of the siting and instrument exposure problems present in USHCN. The close correspondence in nationally averaged temperature from these two networks is further evidence that the adjusted USHCN data provide an accurate measure of the U.S. temperature.
The Menne et al. (2010) results underscore the need to consider all changes in observation practice when determining the impacts of siting irregularities. Further, the influence of non-standard siting on temperature trends can only be quantified through an analysis of the data which do not indicate that the CONUS average temperature trends are inflated due to poor station siting.
Four sets of USCHN stations were used in the Menne et al. (2010) analysis. Set 1 includes stations identified as having good siting by the volunteers at surfacestations.org. Set 2 is a subset of set 1 consisting of the set 1 stations whose ratings are in general agreement with an independent assessment by NOAAÂ’s National Weather Service. Set 3 are those stations with moderate to poor siting ratings according to surfacestations.org. Set 4 is a subset of set 3 consisting of the set 3 stations whose ratings are in agreement with an independent assessment by NOAAÂ’s National Weather Service.
For further information, please see Menne et al. (2010). The set of Maximum Minimum Temperature Sensor (MMTS) stations and Cotton Region Shelter (Stevenson Screen) sites used in Menne et al. (2010) are also available (see the "readme.txt" file as described below for a description of the station list format). Access to the unadjusted, time of observation adjusted, and fully adjusted USHCN version 2 temperature data is described below.
Data Access
U.S. HCN version 2 monthly data are available via ftp at
ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2/monthly/. Please see the "readme.txt" file in this directory for information on downloading and reading U.S HCN v2 data. Version control information is provided in the "status.txt" file.
I'm happy to see your blind hatred prevents you from looking at the evidence. Reinforces my low opinion of you further. NOAA still uses 1500 weather stations but hey don't let a little thing like a fact bother you.
You deniers produce no evidence!!! You maintain no land based temperature stations. You ***** about poorly sited stations and when the stations are removed you ***** about removing stations. You cry like babies that the data from poorly sited stations should not be included in the data sets, and when it is removed from the data sets you whine that the data sets are being adjusted.
Again, why don't you deniers set up your own temperature stations and publish your own data?????????????????????
http://www.ncdc.noaa.gov/oa/climate/research/Peterson-Vose-1997.pdf
3. Duplicate elimination
A time series for a given station can frequently be
obtained from more than one source. For example,
data for Tombouctou, Mali, were available in six different
source datasets. When “merging” data from
multiple sources, it is important to identify these duplicate
time series because 1) the inclusion of multiple
versions of the same station creates biases in areally
averaged temperature analyses, and 2) the same station
may have different periods of record in different
datasets; merging the two versions can create longer
time series.
The goal of duplicate station elimination is to reduce
a large set of n time series (many of which are
identical) to a much smaller set of m groups of time
series that are unique. In the case of maximum and
minimum temperature, 8000 source dataset time series
were reduced to 4964 unique time series. This was
accomplished in the following fashion. First, the data
for every station were compared with the data for every
other station. This naturally started with stations
whose metadata indicated they were in approximately
the same location. Similarity was assessed by computing
the total number of months of identical data as
well as the percentage of months of identical data.
Maximum–minimum temperature time series were
considered duplicates of the same station if they shared
the same monthly value at least 90% of the time, with
at least 12 months of data being identical and no more
than 12 being different. This process identified the
duplicates, which were then merged to form time series
with longer periods of record after a manual inspection
of the metadata (to avoid misconcatenations).
This process was then repeated on the merged dataset
without the initial metadata considerations so every
time series was compared to all the other time series
in the database. Similarity of time series in this step
was judged by computing the length of the longest run
of identical values.
Cases where the time series were determined to be
duplicates of the same station but the metadata indicated
they were not the same station were examined
carefully and a subjective decision was made. This
assessment provided additional quality control of station
locations and the integrity of their data. For example,
a mean temperature time series for Thamud,
Yemen, had 25 yr (1956–81) of monthly values that
were exactly identical to the mean temperature data
from Kuwait International Airport (12° farther north).
Needless to say, one of these time series was in error.
As with most of these problems, determining which
time series was erroneous was fairly easy given the
data, metadata, knowledge about the individual data
sources, duplicate data, and other climatological information
available.
The procedure for duplicate elimination with mean
temperature was more complex. The first 10 000 duplicates
(out of 30 000+ source time series) were identified
using the same methods applied to the maximum
and minimum temperature datasets. Unfortunately,
because monthly mean temperature has been computed
at least 101 different ways (Griffiths 1997), digital
comparisons could not be used to identify the remaining
duplicates. Indeed, the differences between
two different methods of calculating mean temperature
at a particular station can be greater than the temperature
difference from two neighboring stations.
Therefore, an intense scrutiny of associated metadata
was conducted. Probable duplicates were assigned the
same station number but, unlike the previous cases,
not merged because the actual data were not exactly
identical (although they were quite similar). As a result,
the GHCN version 2 mean temperature dataset
contains multiple versions of many stations. For the
Tombouctou example, the six source time series were
merged to create four different but similar time series
for the same station (see Fig. 1).
Preserving the multiple duplicates provides some
distinct benefits. It guarantees no concatenation errors.
Adding the recent data from one time series to the end
of a different time series can cause discontinuities,
unless the mean temperature was calculated the same
way for both time series. It also preserves all possible
information for the station. When two different values
are given for the same station–year–month, it is often
impossible for the dataset compiler to determine which
is correct. Indeed, both may be correct given the different
methods used to calculate mean temperature.
Unfortunately, preserving the duplicates may cause
some difficulty for users familiar with only one “correct”
mean monthly temperature value at a station.
There are many different ways to use data from duplicates.
All have advantages and disadvantages. One
can use the single duplicate with the most data for the
period of interest; use the longest time series and fill
in missing points using the duplicates; average all data
points for that station–year–month to create a mean
time series; or combine the information in more complicated
ways, such as averaging the first difference
(FDyear 1 = Tyear 2 - Tyear 1) time series of the duplicates
and creating a new time series from the average first
difference series. Which technique is the best depends
on the type of analysis being performed.