The large carbon emission from terrestrial ecosystems in 1998: A model simulation

The relationship between the carbon balance of terrestrial ecosystems and climate anomalies in 1998, the warmest year since 1860, was investigated by means of a mechanistic global biosphere model (Sim-CYCLE) based on the plant-production theory. We simulated the monthly time-series and spatial distribution of atmosphere-biosphere CO2 exchange from 1961 to 1998, based on the Sim-CYCLE by inputting the NCEP/NCAR-reanalysis climate data at the spatial resolution of T62 (containing 5828 land pixels after the Matthews biome map). The peculiar climate conditions in 1998, i.e., strong ENSO event and global warming (+0.58 degrees C above the long-term mean), resulted in a remarkable anomaly (as much as 2.7 Pg C yr(-1) of net emission) via the accelerated plant respiration and soil decomposition. The strong sources were in eastern Siberia, northern South America, and South Africa. This anomaly, equivalent to +1.26 ppmv yr(-1) of an increase rate of atmospheric CO2 concentration, can be a major cause of the extraordinarily high CO2 increase rate in 1998.