Publication Date:
2021-04-19
Description:
A variety of proxies have been developed to reconstruct paleo‐CO2 from fossil leaves. These proxies rely on some combination of stomatal morphology, leaf
δ13C, and leaf gas exchange. A common conceptual framework for evaluating these proxies is lacking, which has hampered efforts for inter‐comparison. Here we develop such a framework, based on the underlying physics and biochemistry. From this conceptual framework, we find that the more extensively parameterised proxies, such as the optimisation model, are likely to be the most robust. The simpler proxies, such as the stomatal ratio model, tend to under‐predict CO2, especially in warm (〉15°C) and moist (〉50% humidity) environments. This identification of a structural under‐prediction may help to explain the common observation that the simpler proxies often produce estimates of paleo‐CO2 that are lower than those from the more complex proxies and other, non‐leaf‐based CO2 proxies. The use of extensively parameterised models is not always possible, depending on the preservation state of the fossils and the state of knowledge about the fossil's nearest living relative. With this caveat in mind, our analysis highlights the value of using the most complex leaf‐based model as possible.
Description:
National Science Foundation
http://dx.doi.org/10.13039/100000001
Description:
The Australian Research Council
Keywords:
561
;
CO2
;
leaf gas exchange
;
palaeoclimate
;
proxy
;
stomatal ratio
;
δ13c
Type:
article
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