Response of terrestrial net primary production to climate change associated with the quadrupling CO2 forcing in CMIP6 models

Terrestrial net primary production (NPP) has shown remarkable changes in response to increasing atmospheric CO2 and associated climate change. Many studies have investigated and emphasized the CO2 fertilization effects, while the climatic effects remain uncertain in magnitude and spatial pattern. This study investigates these climatic effects and underlying causes by using outputs of the simulation abruptly quadrupled CO2 from 23 CMIP6 models. We find that tropical terrestrial NPP decreases but extratropical terrestrial NPP increases in response to the CO2-induced climate change. The decreased tropical terrestrial NPP is significantly correlated with the warmer and drier climate anomalies, while the increased extratropical terrestrial NPP is significantly correlated with the warmer and wetter climate anomalies. These results emphasize the climatic effects on terrestrial NPP and reveal the differences among different terrestrial ecosystems, which is favorable for a better understanding of the terrestrial carbon cycle and its coupling with climate.