Drivers of atmospheric CO2 concentrations over glacial to interglacial time scales

Abstract

Atmospheric CO2 concentrations have regularly alternated over the last 650,000 years, between fixed maxima during short interglacial periods and minima over prolonged glacial intervals. This natural variability has taken place alongside major and simultaneous changes in climatic variables, which suggests a strong causal link between climate and CO2. However, the reason for these glacial-interglacial CO2 variations remains difficult to explain. No single mechanism has been identified that accounts for the full range of natural fluctuations of atmospheric CO2. It appears likely that numerous mechanisms have acted in concert. These are likely to encompass physical, biological, and chemical processes and to involve the ocean, given its large carbon reservoir and high turnover rates. Moreover, the challenge is not only to explain the amplitude of glacial-interglacial CO2 variations, but also the complex temporal evolution of atmospheric CO2 and climate.