In Menne at al 2009, they claim that the TOBS adjustments in USHCN2 are the same as in USHCN1.

Nice story but it isn’t true.

ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2/monthly/menne-etal2009.pdf

Note in the graph above that the TOBS adjustment continues to rise from 1990 to the present. In the USHCN1 version, TOBS flattened after 1990

ts.ushcn_anom25_diffs_pg.gif (650×502)

The next graph overlays the most recent TOBS adjustments (blue) on the USHCN 1 graph

As you can see, they have added an extra 0.2 F (60%) on to the TOBS adjustment since USHCN 1. The claims in Menne et al are incorrect.

The USHCN station history file shows almost no changes to temperature observation times after 1990, so it seems quite likely that the USHCN2 post 1990 TOBS upwards adjustments are complete garbage – added on to bring the numbers up.