Summary of GHCN Adjustment-Model Effects on Temperature Data
Guest essay by John Goetz
As the debate over whether or not this year will be the hottest year ever burns on, it is worth revisiting a large part of the data used to make this determination: GHCN v3.
The charts in this post use the dataset downloaded at approximately 2:00 PM on 9/23/2015 from the GHCN FTP Site.
The monthly GHCN V3 temperature record that is used by GISS undergoes an adjustment process after quality-control checks are done. The adjustments that are done are described at a high-level here.
The adjustments are somewhat controversial, because they take presumably raw and accurate data, run it through one or more mathematical models, and produce an estimate of what the temperature might have been given a set of conditions. For example, the time of observation adjustment (TOB) takes a raw data point…
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