Why have the English seasons got in synch?

Back in 1969, I attended a talk by N E Davis covering 100-year cycles he’d found in our local (English? UK?) seasonal temperatures. One thing that was apparent was that the cycles were out of synch with each other; the winter cycle looked to be just past its minimum whilst autumn was just passed the maximum – or would have been if the scorching heat of October 1969 hadn’t messed things up. From these cycles, he seemed fairly confident that there would be late springs for the next fifty years. That prediction started out OK in the early 70s but global warming threw a large spanner in the works.

The following graph of Central England Temperatures, which I’ve smoothed by using a 50-year running mean, shows this pattern of out-of-synch cycles though lengths seem to vary more than I expected from the talk. However, what is remarkable is the way that the anomalies have been in line with each other over the past fifty years or so.
Seasonal anomalies 50-yr

The next graph shows the range between the seasonal anomalies. The latest downward trend in this graph appears to start at the beginning of last century but, due to the 50-year averaging, this could mean the trend could have started in about 1925.
Seasonal anomalies 50-yr range

I confess that I have no idea why this has happened, whether it’s just that it was bound to happen sooner or later or whether global warming might be responsible but I’ve no idea what mechanism would be involved there. Perhaps the cycles, if they existed, were not all the same length and they’ve only recently coincided. I’m stumped.

CET data from Met Office Hadley Centre

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