Unfortunately, your stance is deceptive: Assuming a resolution period of ~120 years (full cycle) or halfcycle (assuming an effective sample every ~120 years, h

Unfortunately, your stance is deceptive: Assuming a resolution period of ~120 years (full cycle) or halfcycle (assuming an effective sample every ~120 years, hence a full cycle period of ~240 years), then the recent excursion can be roughly approximated as a step function. If one lowpasses a step function, you get visible ringing. In the low resolution part of the record there is no ~120 year nor ~240 year ringing at all, so the probability of a similar Heaviside step function theta in temperature having been present but filtered out is nearly zero...