NASA forgot to check the weather reporting from 1921
Part of the process of adjusting historical data to warm the present, is you become at odds with the news and reporting of the day.
NASA shows 1921 as cool. Trouble is historical records show that 1921 was suffering from a global heat wave, food shortages from drought and record heat that lad to cooling until 1971. But that doesn’t fit the alarmism
NASA thinks they didn’t know how to measure the temperature so cooled the past down to make global warming more believable.
Perhaps they should read more.