COP27 Special: 2022 Hottest Year Ever in CET, So Far

I first started analysing the Central England Temperature (CET) record on Uncharted Territory back in 2010, because it seemed to me that, for making historical comparisons, the longer the series, the better. And the CET claims to be the longest. At least one professional agrees with my logic. In particular, of course, a temperature record going back to 1659 allows the significance of global warming to be seen at a glance.

I normally try to wait until data are in rather than try to predict that records will be broken, but COP27 is happening right now, so I thought I’d look at 2022 as a whole, because it is likely to be the hottest calendar year in the CET series, possibly by some margin.

Fig 1 Recent screengrab of CET data year to date for 2022

In Fig 1, I’ve highlighted the comparison with the highest annual CET, which occurred in 2014. The remainder of this year only has to be less than 0.45C anomalously cold to be the hottest on record! And note that the anomaly is compared to the mean for 1961-90, not the mean for recent more globally warmed years. As can be seen in Fig 1, no month in 2022 has yet been colder than the mean for the month in the reference period. Furthermore, mild weather is set to continue to around the middle of November:

Of course, a really cold December like that in 2010 would reduce the annual mean for 2022 significantly. On the other hand, if the weather stays mild, 2022 will be the hottest year by several tenths of a degree C.

As a minor contribution to the discussion around COP27, I thought I’d plot the CET for January to October (adding the means for each month and dividing by 10 – maybe one day I’ll adjust for the number of days in each month, though the difference will be miniscule). For that period 2022 is the hottest year by around 0.3C:

Fig 3 CET January to October mean temperatures, graph by Tim Joslin from Met Office data current (rather than legacy) data

It’s unusual for a record such as the hottest year to be broken by a margin as large as 0.3C, which is obviously what will happen if November and December in 2022 are no colder than in 2014.

Although it’s a fairly arbitrary period, the January to October period in 2022 has also been significantly hotter than in any other year:

RankYearJan-Oct mean temp. (C)
Fig 4 The 10 warmest CET January to October mean temperatures, from Met Office data current (rather than legacy) data

It’s curious that October to January in 1779 was the hottest for so long, especially as temperatures of over even 11C for the first 10 months of the year were so rare in previous centuries:

PeriodYears Jan-Oct CET >= 11CFrequency
Fig 5 Dramatic rise in frequency of CET January to October mean temperatures of 11C or over, from Met Office data current (rather than legacy) data

As can be seen in Fig 3, in fact the January to October CETs over the last 5, 11 and 21 years have all averaged more than 11C, which happened for no such period before 1995-9.