Because I'm a nice guy I'll post this and link it.
How and why the "Record" is limited to 1951 and forward.
Any questions?
How and why the "Record" is limited to 1951 and forward.
Global temperature records start around 1880 because observations did not sufficiently cover enough of the planet prior to that time. The period of 1951-1980was chosen largely because the U.S. National Weather Service uses a three-decade period to define “normal” or average temperature. The GISS temperature analysis effort began around 1980, so the most recent 30 years was 1951-1980. It is also a period when many of today’s adults grew up, so it is a common reference that many people can remember.
https://earthobservatory.nasa.gov/world-of-change/DecadalTemp
Any questions?