Saturday, February 11, 2012

GHCN V3 homogeneity adjustments - revised data.

The previous post was A study of GHCN V3 homogeneity adjustments, Commenter PaulM noted that GHCN had notified a change, with an apparent error in the data version I used. He suggested a recalc, and I think that needs to be done. So here it is. It uses almost the same code as before. There is an issue with a station called COLOSO which seems to be duplicated in the inventory. In the previous version, the unadjusted data file has data for both entries, the adjusted only for one. That required a fix. Now the adjusted file refers to both, so I had to unfix. It's not an issue for here, because the station has little data and falls below the 30-yr threshhold.

Below are the revised histograms and the map. PaulM noted that some of the larger adjustments were moderated - however, the mean adjustment to the trend increased significantly.

Update: The R code to download and generate a CSV file of trend diffs is here

Distribution of trend changes

Again there are three subgroups - stations that have histories with actual reports for at least
  1. 360 months (30 years)
  2. 540 months
  3. 720 months

Mean 0.031 °C/Decade

Mean 0.0302 °C/Decade

Mean 0.0283 °C/Decade

The histograms seem similar, but the means are about 50% higher.

The Google maps app

Details for this app are as previously. I didn't revise the discussion of extreme cases - CORONA NM comes down from about 8 C/Cen to about 6 C/Cen.

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