Possible atmospheric CO2extremes of the Middle Cretaceous (late Albian-Turonian)

摘要: [1] Atmospheric carbon dioxide (CO2) estimates for the Middle Cretaceous (MK) have a range of >4000 ppm, which presents considerable uncertainty in understanding possible causes warmth this interval. This paper examines problem MK greenhouse forcing from an inverse perspective: we estimate upper ocean water temperatures oxygen isotope measurements well-preserved late Albian–Turonian planktonic foraminifera and compare these against predicted by general circulation model (GCM) experiments with CO2 concentrations 500–7500 ppm. At least 4500 ppm is required to match maximum inferred foraminifera. Approximately 900 produces good between minimum temperature MK. An forced two extremes surface conditions brackets nearly all available bottom The climate results support entire proxy data. suggests oceanographic changes deep formation high latitude region one hemisphere other response atmospheric hydrologic cycle strength. We suggest that, rather than contradicting another, various techniques (especially those temporal resolution) may capture true variability that could varied several thousand through