In USHCN V1, older temperatures were considered good, but recent temperatures were adjusted upwards by about 0.5F. After 1990, no further adjustments were considered necessary.
That wasn’t getting the global warming marketing job done, so in USHCN V2 they did the exact opposite. Older temperatures are now cooled, with a hockey stick of adjustments after 1996. The total adjustment is now about 1.5 degrees F, 300% of the V1 adjustments.