Some interesting material over at Climate Audit around the NASA FOI request for emails surrounding McI’s discovery of a mistake in the GISS record post 2000.
As I understand it, Steve McI found an error in the data, which according to Hansen and his colleagues was a result of an error in processing the data. When corrected, the change affected only the US data, not the global data. It had no effect on the ranking of years prior to 2000 and post 2000, it meant a correction of 0.15C.
However, much ado was made of this error.
Here is Steve McIntyre:
Hansen switched from TOBS adjusted versions to raw versions on Jan 1, 2000 without any disclosure of this change to readers and without any scientific justification. It’s nothing to do with throwing out data…That Hansen has made this type of gross programming error in something as extraordinarily simple as a program to merely calculate average temperatures should give pause to anyone assuming that Hansen’s climate model is error-free. The need for a proper arms-length audit of the GISS climate model (or some other equally important model) is obviously a major challenge and, in my opinion, something of very high priority for anyone wanting to rely on these models for policy. [my emphasis]
IT will be interesting to see if GISS apologist, Eli Rabett, comments on this matter.
You can see he suggests this was done on purpose, consciously, and was not an error.
Not only that, but the emails suggest it wasn’t even Hansen who made the error but someone named Reto and that when Reto was going to do a mea culpa, accepting the blame and clearing Hansen, Hansen said no as that would make it look as if Hansen was passing the buck.
Subsequently, Steve McIntyre was lauded as some kind of champion of truth and beauty, and blogospewers claimed that as a result, 1934 and 1998 shifted positions — clearly, according to them, showing that AGW was a hoax or fraud.
In fact, Hansen actually referred to 1934 as the warmest year on record according to GISS in his 2001 paper. So, no. The correction showed no such thing.
What I see happening in this episode is that McI finds a small error, which makes no difference to the ranking of hottest years on US record anyway, and the denialosphere blows it all out of proportion as if this is proof of skullduggery o the part of NASA rather than an innocent error. Then, it gets trumpeted around the blogosphere by people deniers who can’t tell the difference or don’t care to mention the difference between a slight change in the US data post 2000 and a negligible change in global data such that the rankings remain the same, etc.
According to multiple press reports, when NASA corrected the error, the new data apparently caused a reshuffling of NASA’s rankings for the hottest years on record in the United States, with 1934 replacing 1998 at the top of the list. [my emphasis]
This is what Hansen et al actually wrote in 2001:
The U.S. annual (January-December) mean temperature is slightly warmer in 1934 than in 1998 in the GISS analysis (Plate 6). This contrasts with the USHCN data, which has 1998 as the warmest year in the century. In both cases the difference between 1934 and 1998 mean temperatures is a few hundredths of a degree. The main reason that 1998 is relatively cooler in the GISS analysis is its larger adjustment for urban warming. In comparing temperatures of years separated by 60 or 70 years the uncertainties in various adjustments (urban warming, station history adjustments, etc.) lead to an uncertainty of at least 0.1°C. Thus it is not possible to declare a record U.S. temperature with confidence until a result is obtained that exceeds the temperature of 1934 by more than 0.1°C.
The temperature anomaly in the United States in the GISS analysis for 2000 through November is about 0.8°C. This is unusually warm, but it is very unlikely that the U.S. temperature in 2000 will exceed the levels of 1934 or 1998.
The global temperature anomaly for 2000 through November is 0.37°C, which is well below the maximum of 1998. Nevertheless, if we consider the fact that 2000 should have felt the maximum influence of the present long-lived La Niña (see below), it is clear that 2000 was an unusually warm year.
The correction to the GISS data would have no effect on temp before 2000 so I have no idea where this idea came about that now, 1934 was shown to be warmer than 1998.
Perhaps someone with a better understanding of this can correct me if I’m wrong.
Regardless, it really is a case study of a moral panic on the part of global warming skeptics and serious bad faith on the part of deniers.
I’m really so glad that McI posted this — it really does clarify many many things for me.
So thanks Steve McIntyre!