  The climatic controls on the stable carbon isotopic composition (d13C) of
speleothem carbonate are less often discussed in the scientific literature in
contrast to the frequently used stable oxygen isotopes. Various local processes
influence speleothem d13C values and confident and detailed interpretations of
this proxy are often complex. A better understanding of speleothem d13C values
is critical to improving the amount of information that can be gained from
existing and future records. This contribution aims to disentangle the various
processes governing speleothem d13C values and assess their relative
importance. Using a large data set of previously published records we examine
the spatial imprint of climate-related processes in speleothem d13C values
deposited post-1900 CE, a period during which global temperature and climate
data is readily available. Additionally, we investigate the causes for
differences in average d13C values and growth rate under identical climatic
conditions by analysing pairs of contemporaneously deposited speleothems from
the same caves. This approach allows to focus on carbonate dissolution and
fractionation processes during carbonate precipitation, which we evaluate using
existing geochemical models. Our analysis of a large global data set of records
reveals evidence for a temperature control, likely driven by vegetation and
soil processes, on d13C values in recently deposited speleothems. Moreover,
data-model intercomparison shows that calcite precipitation occurring along
water flow paths prior to reaching the top of the speleothem can explain the
wide d13C range observed for concurrently deposited samples from the same cave.
We demonstrate that using the combined information of contemporaneously growing
speleothems is a powerful tool to decipher controls on d13C values ...
