The 2m Temperature (T2m), is the air temperature 2m above the ground. Here the 2-m Temperature from the ERA-5 land re-analysis as provided in the Copernicus Climate Data store is used.
For a quick overview on this data record as provided in the D&V cube, refer to the:
T2m Fact Sheet
For further information please refer to: https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation