NOAA’s US temperature record shows that US was warmest in the 1930’s and has generally cooled as CO2 has increased. This wrecks greenhouse gas theory, so they “adjust” the data to make it look like the US is warming.
The NOAA data tampering produces a spectacular hockey stick of scientific fraud, which becomes the basis of vast amounts of downstream junk climate science. Pre-2000 temperatures are progressively cooled, and post-2000 temperatures are warmed. This year has been a particularly spectacular episode of data tampering by NOAA, as they introduce nearly 2.5 degrees of fake warming since 1895.