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This is of huge importance if the criteria for classifying the stations are recognized as unbiased. The difference between 0.204 C/ decade and 0.324 C/Decade is 59%; i.e. a rather big error. I’ll guess that the error is just as big, if not bigger, in the rest of the world.
However, the importance of your finding depends on whether the objectivity for the classifying criteria can be questioned or not.
Be prepared to be attacked there Antony. The best defense is to give full access to all the data once it is published. Furthermore, that is also the best scientific method.