CET Record For December 2015
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.