Development of new high-resolution pCO2 records for quantifying Earth system climate sensitivity

确定地球系统气候敏感性，即大气中二氧化碳含量加倍引起的全球气温上升量，对于预测大气中二氧化碳含量上升导致的全球气温上升至关重要。我们对这一数值的大部分了解都是基于大气二氧化碳水平不高于今天的时期的数据。该项目将开发新的高分辨率大气二氧化碳记录，与现有温度数据进行比较，以便更好地量化过去6 500万年地球历史中温度与大气二氧化碳水平之间的反应。这一方法将有助于改进对各种大气二氧化碳水平和气候状态（包括冰库和温室条件）的气候敏感性的量化，并将提供更好的信息，以了解如何温度可能会增加，作为未来增加大气二氧化碳的化石燃料燃烧的结果。这项研究将使用大量已发表的碳同位素测量化石陆地有机质和已知的影响pCO 2 C3植物碳同位素分馏，以提供一个新的，高分辨率pCO 2重建使用蒙特卡罗不确定性分析。利用文献中丰富的陆地碳同位素数据，将现有的pCO 2代用数据扩展到更高的分辨率，将有助于改进对不同气候状态下地球系统气候敏感性的估计。这项工作将侧重于：1）晚新生代（30-0 Ma），其特征是pCO 2相对较低，南极冰盖，以及对大气CO2碳同位素组成的严格估计，2）早新生代（66-50 Ma），其特征是温度升高，pCO 2中等偏高，缺乏极地冰盖，以及一系列地质学上短暂的全球变暖事件，即所谓的高温流。

Determination of Earth system climate sensitivity, the amount that global temperatures increase in response to a doubling of atmospheric carbon dioxide levels, is critical towards predicting the increase in global temperatures from rising carbon dioxide levels in the atmosphere. Much of our knowledge of this value is based on data from periods with atmospheric carbon dioxide levels no higher than today. This project will develop new high-resolution atmospheric carbon dioxide records for comparison with existing temperature data in order to better quantify the response between temperature and atmospheric carbon dioxide levels across the last 65 million years of Earth history. This approach will allow for improved quantification of climate sensitivity across a wide range of atmospheric carbon dioxide levels and climate states, including both icehouse and greenhouse conditions, and will provide better information for understanding how temperatures could increase as a result of future increases in atmospheric carbon dioxide from fossil fuel burning.This research will use the large number of published carbon isotope measurements on fossil terrestrial organic matter and the known effects of pCO2 on C3-plant carbon isotope fractionation in order to provide a new, high-resolution pCO2 reconstruction using a Monte Carlo uncertainty analysis. Expansion of the available pCO2 proxy data to significantly higher resolution using the abundance of terrestrial carbon isotope data available in the literature will allow for improved estimates of Earth system climate sensitivity across different climate states. This work will focus on: 1) the late Cenozoic (30-0 Ma), which is characterized by relatively low pCO2, Antarctic ice sheets, and well-constrained estimates of the carbon isotope composition of atmospheric CO2, and 2) the early Cenozoic (66-50 Ma), which is characterized by elevated temperatures, moderate to high pCO2, a lack of polar ice sheets, and a series of geologically brief global warming events known as hyperthermals.