  Annually-resolved measurements of the radiocarbon content in tree-rings have
revealed rare sharp rises in carbon-14 production. These 'Miyake events' are
likely produced by rare increases in cosmic radiation from the Sun or other
energetic astrophysical sources. The radiocarbon produced is not only
circulated through the Earth's atmosphere and oceans, but also absorbed by the
biosphere and locked in the annual growth rings of trees. To interpret
high-resolution tree-ring radiocarbon measurements therefore necessitates
modelling the entire global carbon cycle. Here, we introduce 'ticktack', the
first open-source Python package that connects box models of the carbon cycle
with modern Bayesian inference tools. We use this to analyse all public annual
14C tree data, and infer posterior parameters for all six known Miyake events.
They do not show a consistent relationship to the solar cycle, and several
display extended durations that challenge either astrophysical or geophysical
models.
