Atmospheric CO 2 over the last 1000 years: A high‐resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core

We report a decadally resolved record of atmospheric CO 2 concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre‐industrial period is a rapid ∼7 ppm decrease of CO 2 in a span of ∼20–50 years at ∼1600 A.D. This observation confirms the timing of an abrupt atmospheric CO 2 decrease of ∼10 ppm observed for that time period in the Law Dome ice core CO 2 records, but the true magnitude of the decrease remains unclear. Atmospheric CO 2 variations over the time period 1000–1800 A.D. are statistically correlated with northern hemispheric climate and tropical Indo‐Pacific sea surface temperature. However, the exact relationship between CO 2 and climate remains elusive due to regional climate variations and/or uneven geographical data density of paleoclimate records. We observe small differences of 0 ∼ 2% (0 ∼ 6 ppm) among the high‐precision CO 2 records from the Law Dome, EPICA Dronning Maud Land and WAIS Divide Antarctic ice cores. However, those records share common trends of CO 2 change on centennial to multicentennial time scales, and clearly show that atmospheric CO 2 has been increasing above preindustrial levels since ∼1850 A.D.