It’s an interesting chart. Partly for what it does not show.
There’s been a fair amount of talk about the New Zealand Met Office changing methods and warming their data trend. That may be, but it is not yet in the v3 data, at least by this comparison. Perhaps it is something to look forward to…
Australia, however, has clearly done a lot of “cooling of the past”. Up to 1/2 C much of the time.
I’ve put the two together on one chart just to show how Australia gets changed to have a warming profile more like New Zealand. Kinda makes you go “Hmmmmm” wondering a couple of things. Like, was v1 really that crappy? Or is v3 just out of touch with reality as v1 was pretty good? Was Australia chock full of busted equipment and lousy collection methods until 1990? Or is the change more a result of “diddling the data” than anything wrong in the first place.
At any rate, it does a nice job of showing just how the data can be flopping all over the place on one island country and yet show nothing wrong right next door… Clearly the shifts are not due to some kind of wide spread weather phenomenon that was only now factored in… I also find it less than credible to presume that the same folks who were competent to run a Global Empire and fight in a couple of World Wars on the winning side were not competent to read a thermometer ( so we now have to go back and rewrite their data).
No, the simple fact is that the degree of capricious change in the data, supposedly for the same place (and in fact in many cases the same instruments and same raw data); is as large or larger than the “warming” that is claimed. In fact, for Australia, most of the “warming” being touted today looks to be that 1/2 C from readjusting the data between v1 and v3. Oddly, in the very far past the temperatures are pulled up a great deal. It neatly offsets the degree of adjusting down in the middle and would ‘hide’ it in many statistical searches for bias change.
New Zealand are the blue and orange lines (at the bottom for most of the chart v1 being blue and v3 orange) while Australia are the near black green line for v1 and the red line for v3.
So here we have some clear differences between v1 and v3 in Australia, nearly no change in New Zealand. Which of the 4 lines are correct? If any? The shift or offset looks to have happened about 1971. Wonder what happened then? Or what data was added for then?