A new surface boundary forcing dataset for uncoupled simulations with the Community Atmosphere Model (CAM) is described. The dataset is a merged product based on the monthly mean Hadley Centre sea ice and SST dataset version 1 (HadISST1) and version 2 of the National Oceanic and Atmospheric Administration (NOAA) weekly optimum interpolation (OI) SST analysis. These datasets were also used to supply ocean surface information to the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40). The merged product provides monthly mean sea surface temperature and sea ice concentration data from 1870 to the present, is updated monthly, and is freely available for community use. The merging procedure was designed to take full advantage of the higher-resolution SST information inherent in the NOAA OI.v2 analysis. The Community Atmosphere Model (CAM) is a three-dimensional atmospheric general circulation model (AGCM) used by many scientists for climate research. The CAM serves as the atmospheric component of the Community Climate System Model (CCSM), a fully coupled global climate model. The purpose of this note is to document the global sea surface temperature (SST) and sea ice concentration (SIC) boundary dataset developed for uncoupled simulations with present and future versions of CAM. SST is one of the most important fields in climate system modeling. Fully coupled models allow the ocean to respond to fluctuations in surface heat fluxes driven by atmospheric variability, while uncoupled AGCM experiments use one-way forcing, which is incorrect. The merged dataset was created to address these issues and provide a more accurate and consistent boundary condition for simulations. The dataset was constructed by merging HadISST1 and OI.v2 data, with additional processing to ensure a smooth transition between the products and to eliminate spurious SIC data. The merged dataset is used in the ERA-40 project and is routinely used to monitor climate and evaluate the simulated climates of AGCMs such as CAM. The dataset is updated regularly and is freely available through the National Center for Atmospheric Research's (NCAR) Community Data Portal.A new surface boundary forcing dataset for uncoupled simulations with the Community Atmosphere Model (CAM) is described. The dataset is a merged product based on the monthly mean Hadley Centre sea ice and SST dataset version 1 (HadISST1) and version 2 of the National Oceanic and Atmospheric Administration (NOAA) weekly optimum interpolation (OI) SST analysis. These datasets were also used to supply ocean surface information to the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40). The merged product provides monthly mean sea surface temperature and sea ice concentration data from 1870 to the present, is updated monthly, and is freely available for community use. The merging procedure was designed to take full advantage of the higher-resolution SST information inherent in the NOAA OI.v2 analysis. The Community Atmosphere Model (CAM) is a three-dimensional atmospheric general circulation model (AGCM) used by many scientists for climate research. The CAM serves as the atmospheric component of the Community Climate System Model (CCSM), a fully coupled global climate model. The purpose of this note is to document the global sea surface temperature (SST) and sea ice concentration (SIC) boundary dataset developed for uncoupled simulations with present and future versions of CAM. SST is one of the most important fields in climate system modeling. Fully coupled models allow the ocean to respond to fluctuations in surface heat fluxes driven by atmospheric variability, while uncoupled AGCM experiments use one-way forcing, which is incorrect. The merged dataset was created to address these issues and provide a more accurate and consistent boundary condition for simulations. The dataset was constructed by merging HadISST1 and OI.v2 data, with additional processing to ensure a smooth transition between the products and to eliminate spurious SIC data. The merged dataset is used in the ERA-40 project and is routinely used to monitor climate and evaluate the simulated climates of AGCMs such as CAM. The dataset is updated regularly and is freely available through the National Center for Atmospheric Research's (NCAR) Community Data Portal.