[23throwaway23]

This is how it's typically done: https://www.carbonbrief.org/explainer-how-do-scientists-meas...

There are thousands of measurement stations spread across the globe - on land, in the ocean and in the air.

Four independent datasets are generated by different groups: Scientists use four major datasets to study global temperature. The UK Met Office Hadley Centre and the University of East Anglia’s Climatic Research Unit jointly produce HadCRUT4 .

In the US, the GISTEMP series comes via the NASA Goddard Institute for Space Sciences (GISS), while the National Oceanic and Atmospheric Administration (NOAA) creates the MLOST record. The Japan Meteorological Agency ( JMA) produces a fourth dataset.