The Central England Temperature (CET) is the world’s longest continuous record of temperatures dating back to 1670 and has now been updated by the Met Office to include 2015. December 2015 was the warmest ever recorded, but overall the yearly average is nothing special, reaching just 24th warmest in the series. Ed Hawkins has previously shown that the overall trend in warming for CET is consistent with that shown by the global data (Hadcrut4). However there are some subtle differences evident in the data as well. For example warming started well before 1850. What is of particular interest though is that there has essentially been no warming at all during the summer months for over 350 years!
Most warming has occurred in winter months with smaller trends during spring and autumn. This effect can also be seen in 3 individual monthly trends. Note also the December record set by 2015 as shown below.
Effectively, there is no temperature trend apparent in either August or May, yet December shows a net rise of ~2C over 356 years. Notice also how the year to year variability in December is much higher than either March or August.
Next we look at the yearly averaged CET data
Overall CET shows about a 1C increase in the yearly average, but as we have seen most of that warming has occurred in winter months which also show the most variability. There were often severe winters between the 17th and 19th century when the Thames regularly froze over. More recently 1963 and 2010 were particularly cold, but the overall trend has been for warmer winters on average. Unfortunately those of us looking forward to warmer summers look to be disappointed. 🙁
Cold winters in the UK often coincide with large meanders in the Jet Stream pulling cold polar air down from Siberia across the UK. This usually happens when there are negative phases of the Arctic Oscillation with a less cold stratosphere. Perhaps there has been some long term change in winter polar circulation related to a warmer arctic ?