According to the USHCN V1 docs, they were done adjusting after 1990.
According to the V2 specs, they use the same TOBS algorithm as in V1. So it seems safe to assume that stations with no missing data after 1990 need no adjustments.
1990 was also the year when they started exponentially losing station data, and started doing a lot of infilling.
So I did an experiment. I calculated the post-1990 measured temperatures for all stations with no missing data, and the post 1990 temperatures for all of the fabricated data. The fake data is diverging from the real station data at a phenomenal 5.3 degrees per century.
That huge spike in temperatures after 1990 which NCDC shows (and I asked you to bookmark last night) is almost entirely due to fake data. Unbelievable.
I’ve been talking about the discontinuity after 1990 for a long time, and there you have it.