The Smith & Reynolds Extended Reconstructed Sea Surface Temperature (ERSST) Level 4 dataset provides a historical reconstruction of monthly global ocean surface temperatures and temperature anomalies on a 2 degree spatial grid from 1854-2009 from in-situ observations based on a consistent statistical methodology that accounts for uneven sampling distributions over time and related observational biases. Version 2 of this dataset implements release 2 of ICOADS (International Comprehensive Ocean-Atmosphere Data Set) and utilizes Empirical Orthogonal Teleconnections (EOT) in reconstruction analyses to estimate both surface temperature and associated standard deviation error fields. ERSST v2 presents extended reconstructed sea surface temperature and associated estimated SST error standard deviation fields as 2 similarly structured ASCII flat files.