# wrote on Jan 23
rd, 2014 at 10:59am:
A decade later, in 1991-92 while at the NZ Meteorological Service, I revised the 7SS using a new homogenisation approach to make New Zealand’s temperature records more accurate, such as adjusting for when temperature gauges were moved to new sites.
A new paper on homogenisation
'Effect of data homogenization on estimate of temperature
trend: a case of Huairou station in Beijing Municipality
Abstract
Daily minimum temperature (Tmin) and maximum
temperature (Tmax) data of Huairou station in Beijing from
1960 to 2008 are examined and adjusted for inhomogeneities
by applying the data of two nearby reference stations. Urban
effects on the linear trends of the original and adjusted tem-
perature series are estimated and compared. Results show that
relocations of station cause obvious discontinuities in the data
series, and one of the discontinuities for Tmin are highly
significant when the station was moved from downtown to
suburb in 1996. The daily Tmin and Tmax data are adjusted
for the inhomogeneities. The mean annual Tmin and Tmax at
Huairou station drop by 1.377°C and 0.271°C respectively
after homogenization. The adjustments for Tmin are larger
than those for Tmax, especially in winter, and the seasonal
differences of the adjustments are generally more obvious for
Tmin than for Tmax. Urban effects on annual mean Tmin and
Tmax trends are
−
0.004°C/10 year and
−
0.035°C/10 year
respectively for the original data, but they increase to
0.388°C/10 year and 0.096°C/10 year respectively for the
adjusted data.
The increase is more significant for the annual
mean Tmin series. Urban contributions to the overall trends of
annual mean Tmin and Tmax reach 100% and 28.8% respec-
tively for the adjusted data. Our analysis shows that data
homogenization for the stations moved from downtowns to
suburbs can lead to a significant overestimate of rising trends
of surface air temperature, and this necessitates a careful
evaluation and adjustment for urban biases before the data
are applied in analyses of local and regional climate change.'
http://download.springer.com/static/pdf/243/art%253A10.1007%252Fs00704-013-0894-...my bold
So homogenisation of data is not necessarily a good thing.