Thermometers show that the US has been cooling for 80 years, since the very hot years of the 1930’s
This cooling trend is unacceptable for their theory, funding and political needs, so NCDC simply alters the data to make it look like the US is warming.
The animation below flashed between measured and reported temperature
They accomplish this transformation using a spectacular hockey stick of data tampering, which has skyrocketed since 1980, and is approaching two degrees.
Most of this post-1980 hockey stick appears to be due to loss of rural station data. They use an algorithm where missing temperatures are filled in with temperatures from other stations in the same general geographic area. The missing data is marked in their data set with an ‘E’
In 1980, around 5% of their data was marked with an ‘E’. Now it is over 40%. Most of the missing data is from cooler rural stations, which is then replaced with warmer urban temperatures.
What this does is smear UHI contaminated urban temperatures in with rural temperatures, creating a warming trend which simply doesn’t exist. This enables an entire $29 billion per year industry of meaningless junk climate science.