CO2 and northern hemisphere ice volume variations over the middle and late quaternary

The atmospheric CO2 concentrations have been reconstructed over the past 600 ka based on regression between the Vostok CO2 data and the SPEC-MAP oxygen isotope values. A lag of 4.5 ka (CO2 preceding delta(18)O) gives the best results. A polynomial of order 5 explains 66% of the Vostok CO2 variance over the last 220 ka. The Northern Hemisphere ice-sheet volume was simulated over the past 575 ka using the LLN 2-D model, forced by insolation and these statistically reconstructed atmospheric CO2 concentrations. The simulated ice volume fluctuations resemble the deep-sea oxygen isotope variations. CO2 of interglacial level is necessary for explaining both the interglacial at oxygen isotopic stage 11 and our present-day interglacial.