To glenc,
Have a go at this:
http://www.warwickhughes.com/cool/cool10.htm
Please note trend analyses are meaningless. One needs to use this:
Again, this only shows the inadequacy of using trend lines with climate data. Climate is a chaotic system, subject to unpredictable changes. For climate data, trend lines are useless. Gaussian or other similar averaging is the only thing that will allow us to understand the data. In addition, it is necessary to have long term records to have any chance of understanding what is happening.