Greg Goodman
Taking into account the clear indications in the data that it is not very nice, acknowledging the limits of the tool I’m using, but hoping to clarify a bit, and I hope bring me back to topic.
Picture. Thousand words.
Presents a smoothed approximation of Girma’s derivative curve by taking an actual derivative curve of 5-year smoothed data(plot/best/mean:59/mean:61/derivative/mean:11/mean:13) in blue.
Adds a reference line representing zero (plot/best/scale:0.000001) in red to help the eye discriminate time ranges of rising and falling temperature trends.
Adds a reference plot, scaled and offset to not detract readability of the derivative curve (plot/best/mean:11/mean:13/scale:0.01/offset:0.01).
Looking at the derivative compared to zero, we see a clear change between the last half-century and all that went before on BEST.
The tendency to fall below zero drops dramatically.
This effect detected by eye warrants better formal analysis.
It is marked.
It is of a type that BEST has removed bias for.
From it emerges an indication there may be a real mechanism.
The most obvious reading is that the tendency of temperatures to fall for any appreciable span of time has dropped dramatically in the past fifty years.
Is it real, or spurious, or significant or not?
Does it show a bias in BEST’s method?
That’s up to proper analysis to determine, such as you call for on SST.
The HadSST(2) derivative curve tells a similar story.. and whoa, look at that wartime glitch!