Air trapped in bubbles in polar ice cores constitutes an archive for the re
construction of the global carbon cycle and the relation between greenhouse
gases and climate in the past. High-resolution records from Antarctic ice
cores show that carbon dioxide concentrations increased by 80 to 100 parts
per million by volume 600 +/- 400 years after the warming of the Last three
deglaciations. Despite strongly decreasing temperatures, high carbon dioxi
de concentrations can be sustained for thousands of years during glaciation
s; the size of this phase Lag is probably connected to the duration of the
preceding warm period, which controls the change in land ice coverage and t
he buildup of the terrestrial biosphere.