Climate, pCO2 and terrestrial carbon cycle linkages during late Palaeozoic glacial-interglacial cycles

Earth's last icehouse, 300 million years ago, is considered the longest-lived and most acute of the past half-billion years, characterized by expansive continental ice sheets(1,2) and possibly tropical low-elevation glaciation(3). This atypical climate has long been attributed to anomalous radiative forcing promoted by a 3% lower incident solar luminosity(4) and sustained low atmospheric p(CO2) (<= 300 ppm)(5). Climate models(6), however, indicate a CO2 sensitivity of ice-sheet distribution and sea-level response that questions this long-standing climate paradigm by revealing major discrepancy between hypothesized ice distribution, pCO(2), andgeologic records of glacioeustasy(2,6). Here we present a high-resolution record of atmospheric pCO(2) for 16 million years of the late Palaeozoic, developed using soil carbonate-based and fossil leaf-based proxies, that resolves the climate conundrum. Palaeo-fluctuations on the 10(5)-yr scale occur within the CO2 range predicted for anthropogenic change and co-vary with substantial change in sea level and ice volume. We further document coincidence between pCO(2) changes and repeated restructuring of Euramerican tropical forests that, in conjunction with modelled vegetation shifts, indicate a more dynamic carbon sequestration history than previously considered(7,8) and a major role for terrestrial vegetation-CO2 feedbacks in driving eccentricity-scale climate cycles of the late Palaeozoic icehouse.