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Here are plots of the 3 files at 1990-01-01 00:00 UTC (the extent is larger for the 1st file but regardless):
API method (in °C):
GUI NetCDF format (in K):
GUI GRIB format (in K):
We use R raster::extract() to overlay the point location to the rasters (but we have the same results in QGIS).
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