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CET Record For December 2015

January 2, 2016

By Paul Homewood   



The Central England Temperature numbers are now out for December, confirming what we have known for a while that it has been the warmest such month on record. Last month averaged 9.7C, beating the previous record of 8.1C set in 1934 and equalled in 1974.

Remarkably, there has been a total absence of really mild Decembers in the last couple of decades. Indeed, the last December to make it into the warmest top 20 was in 1988.






As the Met Office has explained in some detail, the unusual warmth was due to an unusual meteorological set up, which not only brought warm air up from the Azores on a powerful jet stream, but did so just about all month.

Comparisons with December 1934 and 1974 are revealing:




Looking at daily data, temperatures in 1934 were similar in the first half of the month, but then declined. In contrast, last month saw temperatures remain high.

This can be seen well on the graph below of cumulative temperature.





We find a slightly different picture in 1974. In that year, as in 1934, the month started warm, but then turned much colder mid month. The last 12 days of the month though were much warmer, with temperatures similar to 2015, as the cumulative chart confirms.






Daily temperatures last month were unusually high, but for the most part were not unprecedented. What really made the difference was the persistence of such temperatures.








  1. January 2, 2016 9:47 pm

    Quite the high outlier and certainly weather related.

    Paul, just curious, do you happen to know how many and which stations were used for the December 2015 CET average?

    Here in Central Texas, the December average temperature was 57.1F (13.9C) at the official NWS Austin Camp Mabry location, which was 4.6F (2.6C) above the 1981-2020 Austin official “normal” of 52.5F (11.4C). The Camp Mabry station began operation July 1, 1999 and the official records were from the old Mueller Airport previously back to 1942 and many other locations going back to 1897. The December average for Camp Mabry 1999-2014 was 53.2F and thus for this location only, December 2015 was 4.1F (2.3C) higher than the 16-year previous monitoring period. The nearby NWS station at Austin Bergstrom Airport had a December average of 55.2F (12.9C) which was 4.8F(2.7C) above the Bergstrom “normal”.

    • January 3, 2016 10:56 am

      Stonyhurst , Pershore College and Rothamsted

      • January 3, 2016 1:43 pm

        Thanks Paul. I will look them up. I’m curious to see exactly where they are located and how long they have records at their current location.

      • January 3, 2016 1:45 pm

        Pershore is in Worcestershire, Stonyhurst in Lancashire, and Rothampstead in Hertfordshire, if that helps.

  2. January 2, 2016 9:59 pm

    Paul, there seems to be an exponentially rising trend in the peaks. But it begins at least in 1850. This is down to deep meanders in the jet stream sucking up warm tropical air. The question needs to be asked what an average Dec temperature means when it is a mix of +15s and +3s.

    We are having a hard time here in Aberdeen, the river Dee just had a 100 year flood. Some friends flooded and river changing course at a number of locations. Combination of rain and melting snow – linked to +15 and +3.

    If you haven’t seen it, this may interest you:

  3. Grimwig permalink
    January 3, 2016 9:14 am

    I have studied the CET for some time but have not been able to determine if it is raw data or adjusted. Certainly UHI should be expected to have some effect where the population of Oxford (a CET site) has risen from around 5,000 to some 50,000 (from memory) over the period. The weather station is hardly ideally sited.

  4. xmetman permalink
    January 3, 2016 11:18 am


    You might like to see this more detailed series of graphs for 2015, including anomalies, percentiles and spells, for a post that I’ve done as a review of CET for 2015.


  5. January 5, 2016 8:00 am

    Despite repeatedly being told that you can’t use one year to “prove” climate change exists, the BBC on this morning’s “Today”, at about 07:20, attempted to do just that.
    The programme is still on air but will be available on iPlayer later.

    “The Met Office expected to confirm this morning that December was the warmest since records began. Professor Myles Allan is head of Oxford University’s Environmental Change Institute.”

    The inherent bias is in the name of the organisation!

  6. Andy DC permalink
    January 5, 2016 2:27 pm

    Very similar pattern for us in the Washington, DC area. We were +11.5 (F) in December and broke the previous record by 5.6 degrees, which was set in 1889.

    As with your December, the warmth was very persistent. The coldest we were the entire month was 31 (F). Roses, cherry blossoms and forsythia have been in bloom for several weeks.

    This morning, it was 16 (F). Nothing extraordinary for January but after all the warmth, it is quite a shock.

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