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Dilbert Made Up Numbers

If the facts don’t suit your agenda, change them! The 18-year “hiatus” in global warming, which has made a shambles of climate model predictions, is now said to have been based on “incorrect data”, according to researchers at National Oceanic and Atmospheric Administration (NOAA). Translation: they have created new data “adjustments” that tell a story more consistent with their preferred narrative, namely, that man-made carbon emissions are forcing global temperatures upward, more or less steadily. The New York Times’ report on the research took a fairly uncritical tone, despite immediate cautions and rebuttals from a number of authorities. On balance, the NOAA claims seem rather laughable.

Ross McKitrick has an excellent discussion of the NOAA adjustments on the Watts Up With That? blog (WUWT). His post reinforces the difficulty of aggregating temperature data in a meaningful way. A given thermometer in a fixed location can yield drifting temperatures over time due to changes in the surrounding environment, such as urbanization. In addition, weather stations are dispersed in irregular ways with extremely uneven coverage, and even worse, they have come and gone over time. There are gaps in the data that must be filled. There might be international differences in reporting practices as well. Sea surface temperature measurement is subject to even greater uncertainty. They can be broadly classified into temperatures collected on buoys and those collected by ships, and the latter have been taken in a variety of ways, from samples collected in various kinds of buckets, hull sensors, engine room intakes, and deck temperatures. The satellite readings, which are a recent development, are accurate in tracking changes, but the levels must be calibrated to other data. Here’s McKitrick on the measurements taken on ships:

… in about half the cases people did not record which method was used to take the sample (Hirahari et al. 2014). In some cases they noted that, for example, ERI readings were obtained but they not indicate the depth. Or they might not record the height of the ship when the MAT reading is taken.

The upshot is that calculating a global mean temperature is a statistical exercise fraught with uncertainty. A calculated mean at any point in time is an estimate of a conceptual value. The estimate is one of many possible estimates around the “true” value. Given the measurement difficulties, any meaningful confidence interval for the true mean would likely be so broad as to render inconsequential the much-discussed temperature trends of the past 50 years.

McKitrick emphasizes the three major changes made by NOAA, all having to do with sea surface temperatures:

  1. NOAA has decided to apply an upward adjustment to bring buoy temperature records into line with ship temperatures. This is curious, because most researchers have concluded that the ship temperatures are subject to greater bias. Also, the frequency of buoy records has been rising as a share of total sea temperature readings.
  2. NOAA added extra weight to the buoy readings, a decision which was unexplained.
  3. They applied a relatively large downward adjustment to temperatures collected by ships during 1998-2000.

Even the difference between the temperatures measured by ships and buoys (0.12 degrees Celsius), taken at face value, has a confidence interval (95%?) that is about 29 times as large as the difference. That adjustments such as those above are made with a straight face is nothing short of preposterous.

A number of other researchers have weighed in on the NOAA adjustments. Carl Beisner summarizes some of this work. He quotes McKitrick as well as Judith Curry:

I think that uncertainties in global surface temperature anomalies is [sic] substantially understated. The surface temperature data sets that I have confidence in are the UK group and also Berkeley Earth. This short paper in Science is not adequate to explain and explore the very large changes that have been made to the NOAA data set. The global surface temperature datasets are clearly a moving target.

There are a number of other posts this week on WUWT regarding the NOAA adjustments. Some of the experts, like Judith Curry, emphasize the new disparities created by NOAA’s adjustments with other well-regarded temperature series. It will be interesting to see how these differences are debated. Let’s hope that the discussion is driven wholly by science and not politics, but I fear that the latter will have a major impact on the debate. It has already.