Philip,
The difference between CET and Winterbourne has been a gradual,
but steady process over the last 27 years - not a jump - which seems to
imply that it is not the change in station location.

Chris

"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message
...

"CHRIS KIDD" wrote:

Birmingham Winterbourne (anomalies based upon 1881-2006 means)

snip

Interesting to note that once again Birmingham Winterbourne has not shown
all-time records as the CET has - in fact since 1971 the CET-Birmingham
has shown an increasing bias which now shows that the CET is +0.4 warmer
than Birmingham...

Chris, are the data normalised, so that the major site change in,
when was it, 1979? does not influence your results? I notice
the mean min anomaly for February is much smaller than
the general anomaly in the Midlands, which is what one would
expect if you are joining Winterbourne and Edgbaston without
homogenising the records. For various reasons, Edgbaston
enjoyed high minimum temperatures. That would also explain
why you are finding a bias in recent decades.

Philip