NOAA NCDC ERSST version4: In situ data: ICOADS2.5 before 2007, NCEP in situ data from 2008 to present. Ice data: HadISST ice before 2015 and NCEP ice after 2015. Resolution: 2x2; Longitude: global; Latitude: global; Time: [Jan 1854,Feb 2020]; monthly