Not what I expected to see. Yet in a way, completely what ought to have been expected.
I plotted the anomaly “by region” using Australia Pacific (region 5) as my test case. Folks may remember I put the time in to match up the old continent / region method of GHNC v3.3 with the nation ID method uses in GHCN v4. I did that just so that I could compare “like to like” graphs.
So the Region 5 (Australia, New Zealand, Philippines, other Pacific Islands) graph at first look didn’t look all that different. It DOES have a spike up at the tail (the new years of data after 2015) that looks very un-physical to me, but the general shape is the same. Then I plotted the two on top of each other. In many cases in the early years the temperature dots are the same dots, but shifted lower. Wait, what? This is an “anomaly” of ONLY a given thermometer in a given month compared to other months of that thermometer. I doubt strongly they went back into the 1800s and “found” more thermometers in the Pacific. So HOW? at present, I can’t say. More “Dig Here!” required. Yet some of the dots move upward around 1900. In the 1940s to about 1975 range, the dots all cluster near the middle and with little difference. Then they spread again after that with some degree of the v4 dots being cooler than the v3.3 dots.
What I’d expected to see was the black dots of the GHCN v3.3 obscuring the red dots of v4 in the early years, then the red v4 pulling up in the present. That’s not what I got.
So here’s the graphs, you tell me what it says:
I really hate it when people re-write historical data.
One thing that I think this DOES illustrate, is that using “anomalies” is not a magic bullet that protects against change in the results from change in the selection of instruments. We’ve got a couple of 1/10 C variation in THE most narrow repeatable anomaly I could make (only comparing a single instrument to itself, in each month). Making an anomaly from different instruments averaged over areas and decades will be more variable. Remember that, in theory, those historical data (pre-W.W.II at least) are FIXED. They can not change in either their actual recorded data or their number. Yet they have.