A Group for High Resolution Sea Surface Temperature (GHRSST) global Level 4 sea surface temperature analysis produced daily on a 0.25 degree grid at the NOAA National Climatic Data Center. This product uses optimal interpolation (OI) using data from the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Version 5 time series (when available, otherwise operational NOAA AVHRR data are used), the Advanced Microwave Scanning Radiometer-EOS (AMSR-E), and in situ ship and buoy observations. A second similar product is available back to 1981 that includes only in situ and AVHRR Pathfinder data in its analysis. The OI analysis is a daily average SST that is bias adjusted using a spatially smoothed 7-day in situ SST average and is thus tuned to about 0.3 meter. Both day and night satellite fields are independently bias adjusted. More information is available at http://www.ncdc.noaa.gov/oa/climate/research/sst/oi-daily.php