This chart of Japanese cherry blossom seasons going back to 812AD seems to support the onset date of the current climate change cycle as happening during the industrial revolution. of the mid-1800's.

Another hockey stick. Also reminding that the Medieval Warm Period was not globally uniform. Warmer in the north Atlantic region, but not in the Far East (though data back then was kind of spotty).

https://en.wikipedia.org/wiki/Medieval_Warm_Period

Cool take. Saw fully blooming cherry blossom trees in a small German town just last week and did the Washington DC peak bloom trip with my kids this time last year. Hadn’t realized we’d have had to plan same trip for April during earlier centuries but it completely makes sense