Investigating the role of temperatures in proxy-based pCO2 estimates: An integrated model-proxy approach

Atmospheric concentrations of carbon dioxide (pCO₂) play a critical role in a number of earth system components, including the biosphere, geosphere, and atmosphere. Understanding how pCO₂ has changed over geologic time may provide critical context for predicting future climate scenarios. However, constraining past pCO₂ values remain a challenge in paleoclimate studies due to difficulties in constraining proxy calculation parameters. Marine-based pCO₂ proxies rely on at least one temperature parameter (i.e., via Henry’s Law to convert dissolved CO₂ concentrations from the ocean into atmospheric pCO₂), which is difficult to constrain in deep-time. Here, we highlight the importance of temperature and propose a new method of model-derived temperatures based on the paleo-location of the sample site. This methodology can be applied to any pCO₂ proxy with temperature input; here we use the example of the pCO₂ proxy based on the stable carbon isotopic composition of phytane, the diagenetic product of chlorophyll-a, due to its spatial and temporal ubiquity over the past ca. 465 million years.