NASA has doubled 1890-1980 global warming since 1981, simply by altering their data set progressively over time.
But it is worse than it seems. Let’s focus on the changes from 2002 to 2014
Note on the pre-1950 changes, they have altered the data well beyond their own error bars, which are the blue lines in the 2002 graph and the green lines in 2014 graph.
They pretend to be doing something mathematically rigorous, when in fact they are simply manipulating data to suit a political agenda. Policy Based Evidence Making