I recently wrote up, and submitted to the Social Science Research Network, a study of the Central England Temperature series that I did a couple of years ago and recently updated. You can access the paper at the SSRN here: A Seasonal Autoregressive Model for the Central England Temperature Series.
What I do in this analysis is build a seasonal autoregressive model for what is the longest time series of directly measured temperatures available for analysis. This model includes a linear trend component. I fit the model for both the pre-Industrial Revolution Period (1659 to 1849) and the Post-Industrial Revolution period (1949 to 1999). In the former period no trend is apparent, in the latter period I find a warming trend of 1 °C/century. This result has a borderline statistical significance (less than 3σ). I use both models to forecast the temperatures for the 21st. Century and find that the older, trend free, model does a slightly better job out-of-sample than the newer model with the trend.