The history of climate scientists adjusting data to try to make recent warming look greater than it really is goes back quite a long way.
It’s a regular topic at Paul Homewood’s blog for example. But climate scientists continue to do it, giving the sceptics plenty of ammunition. Here are three recent blog posts discussing how climate scientists continue to adjust data to exaggerate warming.
At Pierre Gosselin’s blog there’s a guest post by Kirye from Japan, on NASA GISS temperature adjustments. In the latest GISS version, V4, the supposedly “unadjusted” data sets are different from the unadjusted data in the previous version V3.
Tony Heller has a graph of the 2000, 2017 and 2019 version of NASA GISTEMP, showing that Gavin Schmidt and his team have managed to crank up warming, particularly in the era of the inconvenient pause. You can also see this effect in fig 2 and fig 4 of the GISS history page.
Here in the UK, the HadCRUT4 team are doing the same thing. Clive Best asks Whatever happened to the Global Warming Hiatus? The answer is that they have demolished it with a sequence of adjustments to the data. HadCRUT3, as published in 2014, shows a clear pause, with no warming from about 2001-2013, but the latest new improved data set HadCRUT4.6 cranks recent temperatures upwards. Clive thought that night be due to including different measurement stations, but checked and found that was not the case. The numbers have simply been adjusted.
The previous versions of HadCRUT4 are available here. From these you can see how the temperature difference between 2013 and 2001 has been steadily nudged upwards in successive versions:
But the main point of this post (the 4th ‘again’ in the title) is to report on the very latest data fiddle, not mentioned in any of the above posts. This comes from John Kennedy and colleagues from the Met Office, and is described in a very long paper recently made available here. This is concerned with sea surface temperatures (SSTs) and the brand new data set is called HadSST4 (confusingly, HadCRUT4 uses HadSST3).
Here is Fig 14 from the paper. The axis label is on a lower plot, but the big tick marks are 1850, 1900, 1950, 2000. The graph compares the current version HadSST3 with the proposed new one, HadSST4.
Obviously, I don’t need to explain which is the new version and which is the previous one. Warming has simply been tweaked upwards by about 0.1C, or about 10% of the total.
Figure 16 shows temperature trends from the year marked up until 2012:
Here the red diamond is the raw data, the green diamond is HadSST3, and the new HadSST4 is shown as the black line, with grey shading representing uncertainty. In the early years of the 20th century, there was global warming that doesn’t fit with the carbon-dioxide-controlled theory of climate scientists, so that is adjusted downwards. But look at the trend over the pause era, since 2000.