NOAA/WDS Paleoclimatology - Global Atmospheric CO2 Growth Rate Reconstruction over the Past Nine Centuries

Interannual atmospheric CO2 growth rate (CGR), mostly resulting from fluctuating carbon uptake in terrestrial biosphere, is a key determinant of atmospheric CO2 concentration. However, CGR observations are merely available in recent decades, which are unable to fully reveal its natural variability and interactions with terrestrial ecosystems and climatic drivers. Here we present a reconstruction of interannual CGR over the past nine centuries (1100-2006) based on a globally distributed temperature-sensitive proxy network. The reconstruction is validated by the comparison with dynamic global vegetation model simulations and the El Niño-Southern Oscillation. Our data reveal a close association of CGR variability with atmospheric CO2 concentration and tropical climate. Present CGR variability is unprecedentedly high over the past nine centuries, suggestive of the instability of present carbon cycle and the reducing resilience of atmospheric carbon balance under intensifying anthropogenic forcing. Our record provides a pre-industrial constraint for perceiving the climate-carbon coupling under historical climate forcings.