Global monthly mean sea-surface temperature (SST) anomalies relative to a 1961–90 climatology from satellites (ATSRs: Along-Track Scanning Radiometers) and in-situ records (HadSST3). Black lines: the 100-member HadSST3 ensemble. Red lines: ATSR-based night-time subsurface temperature at 0.2 m depth (SST0.2m) estimates from the ATSR Reprocessing for Climate (ARC) project. Retrievals based on three spectral channels (D3, solid line) are more accurate than retrievals based on only two (D2, dotted line). Contributions of the three different ATSR missions to the curve shown are indicated at the bottom. The in-situ and satellite records were collocated within 5×5° monthly grid boxes: only those where both datasets had data for the same month were used in the comparison. (Adapted from Merchant et al. 2012.)