Deplorable clomate science blog:

Most of these adjustments are due to simply making up data. Every month, a certain percentage of the 1,218 United States Historical Climatology Network (USHCN) stations fail to report their data, and the temperature gets estimated by NOAA using a computer model. Missing data is marked in the USHCN database with an “E” – meaning “estimated.” In 1970, about 10% of the data was missing, but that number has increased to almost 50%, meaning that almost half of the current adjusted data is fake.