This week in #CoolClimateData we’re continuing our dive into the large collection of up-to-date climate data hosted by Professor Ole Humlum at Climate4you.com. Today it’s the compilation of surface air temperature data sets, which Professor Humlum divides into three quality classes. In the first class are the satellite data sets we discussed last week, where Humlum has long pointed to the UAH data set as the most reliable, a judgment recently confirmed by NOAA scientists. The second and third quality classes are temperature datasets based on thermometer measurements on land and sea. He judges the best of these to be that produced by the Hadley Centre in the UK, which is called the HadCRUT record. (This frankly ugly half-acronym is for the Hadley Centre/ University of East Anglia Climate Research Unit Temperature measure.) Humlum favours their ocean record because it does a better job of matching the Argo float record, another cool data set we’ll discuss later. Mind you, like all the thermometer-based data sets HadCRUT shows the imprint of much monkeying around and “adjustments”. But they aren’t as bad as the kludges applied to the other data sets, which in modern climate science is actually praise.
The HadCRUT4 record since 1979 looks like this:
As you see, there was a warming trend through the 1980s and 1990s, then the famous, if contentious, “hiatus,” a long pause until 2016 when an El Niño caused a big warming spurt, after which the record has been gradually settling down ever since.
Humlum produces what he calls “maturity” diagrams, in which he compares the current version of the data to the version the same team published in 2008. If the data are being tweaked to show a greater warming trend, it would show up as cooling adjustments in the current version for earlier years and warming adjustments for later ones.
In the case of the HadCRUT record, the adjustments do indeed add a bit of a trend, as illustrated by this chart which shows not temperatures or temperature changes, but adjustments to the temperature by year. It was produced by taking the 1850-2008 HadCRUT record as it is currently published and subtracting the same HadCRUT record as published in 2008. So if a given year is red it means the current HadCRUT figure for that year is higher than their 2008 figure and if blue that it’s cooler:
Suspiciously, there’s a lot of blue before 1980, especially after 1895, indicating cooling adjustments, though also a lot of red. But from 1980 onward they are all warming adjustments. And it’s noteworthy that the period from 1940 to 1975, when falling temperatures triggered a cooling scare despite rising CO2, seems to have been, well, adjusted upward. But at least there are warming adjustments in the 1800s as well.
Now here’s the same chart but for the NASA global temperature record rather than the HadCRUT. And it indicates a much bigger hot red thumb on the scale:
The IPCC and climate science crowd see nothing wrong with all the adjustments and manipulations of the temperature record, even when the apparent warming trend turns out to be mainly a result of fudging the numbers. Which is not cool, especially since if you asked a group of competent statisticians to create the adjustment chart you’d expect if someone were manufacturing a warming trend you’d pretty much get the one immediately above.
So we prefer to use the satellite record whenever possible, in line with Professor Humlum’s recommendation.