This product is developed at the Oregon State University, its home page is here:
It provides monthly or weekly Net Primary Production global maps with a resolution of 1/6degree or 1/12 (!) from 1997-2007 (using SeaWIFS chlorophyll) and 2002-2007 (using MODIS chlorophyll).
It is based on a misc of datas (chlorophyll, SST, radiative forcing) and a model (Vertically Generalized Production Model, VGPM, Behrenfeld & Falkowski 1997a). It's all well explained on their website.
After downloading the monthly Standard SeaWIFS based estimate (here: http://orca.science.oregonstate.edu/1080.by.2160.monthly.hdf.vgpm.s.chl.a.sst.php) in hdf format, I converted it in netcdf using the matlab function hdf2netcdf.m you'll find at the bottom of this page and then blended the whole monthly time serie into a single netcdf file using another matlab script (again attached to this page). The single netcdf file is 1.1 Go size.
Photosynthetic Rates Derived from Satellite-Based Chlorophyll Concentration
Mean NPP 1998-2007