As of 1975, scientists showed no net warming from 1900 to 1970
But now they show a lot of warming from 1900 to 1970.
NASA has massively changed their data many times.
They have altered data outside their own error bounds.
Surface temperatures and radiosonde have been massively diverging. The vast majority of reported warming since 1980 is due to Urban Heat Island effects.
They are losing rural station data, and infilling it with urban data
The global surface temperature record is complete crap, and has no business being used by scientists other than as a case study in UHI confirmation bias.