Using AATSR data to assess the quality of in situ sea-surface temperature observations for climate studies

► Observational uncertainties in in situ and AATSR data were estimated. ► Correlated in situ observational errors lead to larger uncertainties. ► Ships SST measurements are biased warm relative to drifting buoy SSTs. ► Increase in drifting buoy numbers artificially lowers global average SST trend.