The Terrestrial Ecosystem Model (TEM version 4.1) is applied to assess the sensitivity of net ecosystem production (NEP) of the terrestrial biosphere to transient changes in atmospheric CO2 concentration and climate in the 21st century. These NEP estimates provide a measure of the potential for various vegetated regions and countries to act as sinks or sources of atmospheric CO2. We use three transient climate change predictions over the period of 1977-2100 from the MIT Integrated Global System Model for assessment of the effects of different climate changes. Global annual NEP has large interannual variations and increases over time, thus representing a growing net carbon flux from the atmosphere to the biosphere. Latitudinal distribution of total annual NEP along 0.5 degree resolution latitudinal bands has a significant shift from the tropics to the northern mid- and high-latitudes over time. The sums of annual NEP over the period of 1990-2100 differ substantially among the twelve economic regions of the world. The results show that temporal dynamics and spatial distribution of annual NEP are very sensitive to the magnitudes and paths of temporal changes in atmospheric CO2 concentration and climate.