What is a temperature anomaly? The term temperature anomaly means a departure from a reference value or long-term average. A positive anomaly indicates that the observed temperature was warmer than the reference value, while a negative anomaly indicates that the observed temperature was cooler than the reference value. https://www.ncdc.noaa.gov/monitoring-references/faq/anomalies.php
I'd still like to know just how they got the"Global" & "Hemisphere" temps back in 1880. How do you know what the global temps were in 1983? There were no satellites, no sophisticated instrumentality. Did they really have pro & amateur meteorologist all around the entire planet in 1890 with calibrated instruments?
Come on tell me ... I know you can..... Tell me just how all those people calibrated their little thermometers all around the world in the 1800s
"Some of the principles of the thermometer were known to Greek philosophers of two thousand years ago. The modern thermometer gradually evolved from the thermoscope with the addition of a scale in the early 17th century and standardisation through the 17th and 18th centuries.[1][2][3]" https://en.wikipedia.org/wiki/Thermometer
I thought the history snippet would answer your question. Noted, by the way, your derisive "little thermometers". Anyway, people were standardizing thermometers in the 17th and 18th centuries, which is 100-200 years of practice for standardizing them "in the 1800s" (19th century).