Not exact matches
There are a pair of diodes on each winding, one up, one down, so you
get clipped dc output on both halves of the
sine wave that winding puts out.
fitting only to least sum squares (blue dots) I
get a change in temperature that looks like a
sine -
wave with a peak to peak of 60 - 70 years.
In fact, you can
get a very good fit with actual temperature by modeling them as three functions: A 63 - year
sine wave, a 0.4 C per century long - term linear trend (e.g. recovery from the little ice age) and a new trend starting in 1945 of an additional 0.35 C, possibly from manmade CO2.