LINKING A GLOBAL TERRESTRIAL BIOGEOCHEMICAL MODEL AND A 2-DIMENSIONALCLIMATE MODEL - IMPLICATIONS FOR THE GLOBAL CARBON BUDGET

We used the terrestrial ecosystem model (TEM, version 4.0) to estimate global responses of annual net primary production (NPP) and total car bon storage to changes in climate and atmospheric CO2, driven by the c limate outputs from the 2-dimensional MIT L-O climate model and the 3- dimensional GISS and GFDL-q atmospheric general circulation models (GC Ms). For contemporary climate with 315 ppmv CO2, TEM estimates that gl obal NPP is 47.9 PgC/yr and global total carbon storage is 1658 PgC: 9 08 PgC of vegetation carbon and 750 PgC of reactive soil organic carbo n. For climate change associated with a doubling of radiative forcing and an atmospheric level of 522 ppmv CO2, the responses of global NPP are +17.8% for the MIT L-O climate, +18.5% for the GFDL-q climate and +20.6% for the GISS climate. The responses of global total carbon stor age are +6.9% for the MIT L-O climate, +8.3% for GFDL-q climate and +8 .7% for the GISS climate. Among the three climate change predictions, the changes in latitudinal distributions of cumulative NPP and total c arbon storage along 0.5 degrees latitudinal bands vary slightly, excep t in high latitudes. There are generally minor differences in cumulati ve NPP and total carbon storage for most of the 18 biomes, except for the responses of total carbon storage in boreal biomes for the 2-D ha L-O climate change. The results demonstrate that the linkage between t he TEM and the 2-D climate model is useful for impact assessment and u ncertainty analysis within an integrated assessment framework at the s cales of the globe, economic regions and biomes, given the compromise between computational efficiency in the 2-D climate model and more det ailed spatial representation of climate fields in 3-D GCMs.