The Coral Reef Temperature Anomaly Database (CoRTAD) is a collection of sea surface temperature (SST) and related thermal stress metrics, developed specifically for coral reef ecosystem applications but relevant to other ecosystems as well. The CoRTAD Version 4 contains global, approximately 4 km resolution SST data on a weekly time scale from 1981 through 2010. Version Changes: Version 4, 1981-10-31 - 2010-12-31, Global 4320x8640, Tile 540x540, NetCDF-4 Classic Version 3, 1982-01-01 - 2009-12-31, Global 4096x8192, Tile 512x512, HDF5 Version 2, 1982-01-01 - 2008-12-31, Global 4096x8192, Tile 512x512, HDF5 Version 1, 1985-01-01 - 2005-12-31, Global 4096x8192, Tile 512x512, HDF4 NODC Accession Numbers: v3 0068999; v2 0054501; v1 0044419 CoRTAD 4 is derived from Pathfinder 5.2 Sea Surface Temperatue, while CoRTAD 3 utilized Pathfinder 5.1 and 5.0. CoRTAD 4 has 14 extra months of data, 11 percent more pixels and is produced in NetCDF-Classic format compared to CoRTAD 3. CoRTAD 4 has slightly improved harmonics and contains additional metadata. CoRTAD 4 is compliant with version 1.0 of NODC's NetCDF templates (http://www.nodc.noaa.gov/data/formats/netcdf). In addition to SST, the CoRTAD contains SST anomaly (SSTA, weekly SST minus weekly climatological SST), thermal stress anomaly (TSA, weekly SST minus the maximum weekly climatological SST), SSTA Degree Heating Week (SSTA_DHW, sum of previous 12 weeks when SSTA >= 1 degree C), SSTA Frequency (number of times over the previous 52 weeks that SSTA >= 1 degree C), TSA DHW (TSA_DHW, also known as Degree Heating Week, sum of previous 12 weeks when TSA >= 1 degree C), and TSA Frequency (number of times over previous 52 weeks that TSA >=1 degree C). The CoRTAD was created at the NOAA National Oceanographic Data Center in partnership with the University of North Carolina - Chapel Hill, with support from the NOAA Coral Reef Conservation Program. The purpose of the CoRTAD is to provide sea surface temperature data and related thermal stress parameters with good temporal consistency, high accuracy, and fine spatial resolution. The CoRTAD is intended primarily for climate and ecosystem related applications and studies and was designed specifically to address questions concerning the relationship between coral disease and bleaching and temperature stress.