Thoughts on the GISS temperature adjustment
There has been a lot of blogging recently about the problem with the temperature record for the continental U.S. RealClimate described the problem thusly:
Last Saturday, Steve McIntyre wrote an email to NASA GISS pointing out that for some North American stations in the GISTEMP analysis, there was an odd jump in going from 1999 to 2000. On Monday, the people who work on the temperature analysis (not me), looked into it and found that this coincided with the switch between two sources of US temperature data. There had been a faulty assumption that these two sources matched, but that turned out not to be the case. …
The net effect of the change was to reduce mean US anomalies by about 0.15 ºC for the years 2000-2006. There were some very minor knock on effects in earlier years due to the GISTEMP adjustments for rural vs. urban trends. In the global or hemispheric mean, the differences were imperceptible (since the US is only a small fraction of the global area).
A few comments about this:
First, events like this are the reason scientists look for confirmation of a claim in multiple data sets before the scientific community confidently accepts that claim. Any single data set could contain unknown errors. But it’s far less likely that multiple, independent data sets are all wrong, and in the same direction — so agreement of multiple, independent data sets in support of a claim provides a strong verification of that claim.
For the claim that the earth is warming, the evidence comes not just from the surface thermometer record, but also: satellite measurements of increasing temperatures, observations of receding glaciers, observations of decreases in Arctic sea ice extent and thickness, increases in ocean heat content, increases in sea level, and paleoproxy data.
The evidence of warming is therefore overwhelming, and this correction has little impact on that (and, besides, this correction only affects the continental U.S. data, which has relatively little effect on the global average).
Second, some commenters have suggested that because the U.S. is one of the best instrumented countries, there must be even bigger errors in data from other parts of the world. This argument, however, makes no sense. The problem that was identified was a software error — it was not related to the quality of the measurement network. There is no reason to conclude from this error that errors exist in other data sets.
Third, given the high stakes of the debate, I think all scientists working on the climate change problem need to accept the fact that there are going to be lots of people looking over our shoulders at our research. We need to graciously accept that fact, for both practical and philosophical reasons.
From a practical standpoint, complaining about this looks bad. It makes us look like we are hiding something, particularly when it comes after someone uncovered an actual mistake. And philosophically, the vast majority of climate research is paid for with tax dollars. As a result, we have an obligation to make our work available in formats that the public wants. That would run the gamut from a summary written for the lay reader to the actual raw data.
If a scientist really doesn’t want any public scrutiny of their work, they should switch to a subject that no one cares about, like string theory.