Changes

The three groups take raw data, and they "homogenize" it to remove things like when a station was moved to a warmer location. The three global temperature records are usually called CRU, GISS, and GHCN. Both GISS and CRU, however, get almost all of their raw data from GHCN. All three produce very similar global historical temperature records from the raw data. One of the things that was revealed in the released CRU emails is that the CRU basically uses the Global Historical Climate Network (GHCN) data set for its raw data.<ref>[http://www.climate-gate.org/search.php?keyword=GHCN&topEmails=&submit=Search Search - GHCN], climate-gate.org, Climategate Document Database.</ref> But the [[IPCC]] uses the "adjusted" data; GHCN adjusts the data to remove what it calls "inhomogeneities." Inhomogeneity are defined in a quote from GHCN:

The three groups take raw data, and they "homogenize" it to remove things like when a station was moved to a warmer location. The three global temperature records are usually called CRU, GISS, and GHCN. Both GISS and CRU, however, get almost all of their raw data from GHCN. All three produce very similar global historical temperature records from the raw data. One of the things that was revealed in the released CRU emails is that the CRU basically uses the Global Historical Climate Network (GHCN) data set for its raw data.<ref>[http://www.climate-gate.org/search.php?keyword=GHCN&topEmails=&submit=Search Search - GHCN], climate-gate.org, Climategate Document Database.</ref> But the [[IPCC]] uses the "adjusted" data; GHCN adjusts the data to remove what it calls "inhomogeneities." Inhomogeneity are defined in a quote from GHCN:

{{cquote|Most long-term climate stations have undergone changes that make a time series of their observations inhomogeneous. There are many causes for the discontinuities, including changes in instruments, shelters, the environment around the shelter, the location of the station, the time of observation, and the method used to calculate mean temperature. Often several of these occur at the same time, as is often the case with the introduction of automatic weather stations that is occurring in many parts of the world. Before one can reliably use such climate data for analysis of long term climate change, adjustments are needed to compensate for the non-climatic discontinuities.<ref name=dataintegrity/>}}  

{{cquote|Most long-term climate stations have undergone changes that make a time series of their observations inhomogeneous. There are many causes for the discontinuities, including changes in instruments, shelters, the environment around the shelter, the location of the station, the time of observation, and the method used to calculate mean temperature. Often several of these occur at the same time, as is often the case with the introduction of automatic weather stations that is occurring in many parts of the world. Before one can reliably use such climate data for analysis of long term climate change, adjustments are needed to compensate for the non-climatic discontinuities.<ref name=dataintegrity/>}}  

At Darwin Airport there are five separate individual station records that are combined to make up the final Darwin record.<ref>[http://data.giss.nasa.gov/cgi-bin/gistemp/findstation.py?datatype=gistemp&data_set=0&name=darwin GISS Surface Temperature Analysis], data.giss.nasa.gov.</ref> This raw data is downloaded from GISS, but GISS uses the GHCN raw data as the starting point for their analysis. Before the GHCN homogenized the data, temperatures in Darwin were falling at 0.7 Celcius per century. After the homogenization, they were warming at 1.2 Celcius per century. Darwin is an ideal station because it also illustrates many of the problems with the raw temperature station data.

At Darwin Airport there are five separate individual station records that are combined to make up the final Darwin record.<ref>[http://data.giss.nasa.gov/cgi-bin/gistemp/findstation.py?datatype=gistemp&data_set=0&name=darwin GISS Surface Temperature Analysis], data.giss.nasa.gov.</ref> This raw data is downloaded from GISS, but GISS uses the GHCN raw data as the starting point for their analysis. Before the GHCN homogenized the data, temperatures in Darwin were falling at 0.7 Celcius per century. After the homogenization, they were warming at 1.2 Celcius per century.  

The record seems to be screwed up around 1941. Although the 1941 temperature shift seems large, a similar sized shift occurred from 1992 to 1999. Willis Eschenbach looked into it further to see how Darwin homogenized each of the individual station records that created the average of the homogenized Darwin records. Eschenbach started with the earliest record, "Station Zero" at Darwin. The five different station records (raw data) covering Darwin from 1941 on all agreed almost exactly. What Eschenbach found was that the "homogenized" data has been adjusted to fit someone’s preconceptions about whether the earth is warming.

Willis Eschenbach looked into it further to see how Darwin homogenized each of the individual station records that created the average of the homogenized Darwin records. Eschenbach started with the earliest record, "Station Zero" at Darwin. The five different station records (raw data) covering Darwin from 1941 on all agreed almost exactly. What Eschenbach found was that the "homogenized" data has been adjusted to fit someone’s preconceptions about whether the earth is warming.

{{cquote|They’ve just added a huge artificial totally imaginary trend to the last half of the raw data! ... [A] six degree per century trend? What’s up with that? ... [T]he GHCN adjusted Station 1 to match Darwin Zero’s strange adjustment, but they left Station 2 totally untouched. They only homogenized two of the three. Then they averaged them. That way, you get an average that looks kinda real, I guess, it 'hides the decline.' ... Care to know the way that GISS deals with this problem? Well, they only use the Darwin data after 1963, a fine way of neatly avoiding the question ... and also a fine way to throw away all of the inconveniently colder data prior to 1941. ... Every time the data gets revised and homogenized, the trends keep increasing. What this does show is that there is at least one temperature station where the trend has been artificially increased to give a false warming where the raw data shows cooling.<ref name=dataintegrity/>}}

{{cquote|They’ve just added a huge artificial totally imaginary trend to the last half of the raw data! ... [A] six degree per century trend? What’s up with that? ... [T]he GHCN adjusted Station 1 to match Darwin Zero’s strange adjustment, but they left Station 2 totally untouched. They only homogenized two of the three. Then they averaged them. That way, you get an average that looks kinda real, I guess, it 'hides the decline.' ... Care to know the way that GISS deals with this problem? Well, they only use the Darwin data after 1963, a fine way of neatly avoiding the question ... and also a fine way to throw away all of the inconveniently colder data prior to 1941. ... Every time the data gets revised and homogenized, the trends keep increasing. What this does show is that there is at least one temperature station where the trend has been artificially increased to give a false warming where the raw data shows cooling.<ref name=dataintegrity/>}}