Comparing global models of terrestrial net primary productivity (NPP): overview and key results

W. Cramer, D. W. Kicklighter, A. Bondeau, B. Moore Iii, G. Churkina, B. Nemry, A. Ruimy, A. L. Schloss, ThE. Participants OF. ThE. Potsdam Intercomparison
1999 Global Change Biology  
Seventeen global models of terrestrial biogeochemistry were compared with respect to annual and seasonal¯uxes of net primary productivity (NPP) for the land biosphere. The comparison, sponsored by IGBP-GAIM/DIS/GCTE, used standardized input variables wherever possible and was carried out through two international workshops and over the Internet. The models differed widely in complexity and original purpose, but could be grouped in three major categories: satellite-based models that use data
more » ... the NOAA/AVHRR sensor as their major input stream (CASA, GLO-PEM, SDBM, SIB2 and TURC), models that simulate carbon¯uxes using a prescribed vegetation structure (BIOME-BGC, CARAIB 2.1, CENTURY 4.0, FBM 2.2, HRBM 3.0, KGBM, PLAI 0.2, SILVAN 2.2 and TEM 4.0), and models that simulate both vegetation structure and carbon¯uxes (BIOME3, DOLY and HYBRID 3.0). The simulations resulted in a range of total NPP values (44.4±66.3 Pg C year ±1 ), after removal of two outliers (which produced extreme results as artefacts due to the comparison). The broad global pattern of NPP and the relationship of annual NPP to the major climatic variables coincided in most areas. Differences could not be attributed to the fundamental modelling strategies, with the exception that nutrient constraints generally produced lower NPP. Regional and global NPP were sensitive to the simulation method for the water balance. Seasonal variation among models was high, both globally and locally, providing several indications for speci®c de®ciencies in some models.
doi:10.1046/j.1365-2486.1999.00009.x fatcat:odwskihsufgwzb2i5k4sw75ade