The most useful resource for geospatially explicit global historical population data is the HYDE data set produced by the Netherlands environmental assessment agency (MNP) (PDF summary). Version 3.1 is at 5′ resolution and covers the entire Holocene era from 10,000 BC to 2005 A.D (download). HYDE 3.1 will be used in the Fifth Assessment Report by the IPCC.
For future population projections, the best options are GPW 2015, GPW 2035 and population projections for 2050 – 2080 by IIASA (the latter two will be available from SEDAC and ISciences via TerraViva! later in 2009).
Gridded Global Population Datasets: LandScan and GPW | Global Data Hound // Apr 23, 2009 at 2:51 pm
[...] there are only two widely accepted, geospatially explicit, gridded data sets describing the current* population of the entire globe. Why only two? It’s not as if the population of the world is [...]