Tipping Points in the Climate System: Automatic Detection of Abrupt
Transitions in Paleoclimate Records
Abstract
Bifurcations and tipping points (TPs) are an important part of the Earth
system’s behavior. These critical points represent thresholds at which
small changes in the system’s parameters or in the forcing abruptly
switch the system from one state or type of behavior to another. Current
concern with TPs is largely due to the potential contribution of
anthropogenic forcing to one or more climatic subsystems undergoing such
abrupt, and possibly irreversible, transitions. Paleorecords of past
climate have been shown to contain abrupt transitions, or “jumps,”
which may represent former instances of tipping. Robustly identifying
and describing such transitions is essential to properly understanding
the underlying bifurcation mechanisms. Doing so may provide valuable
information for identifying critical TPs in current and future climate
evolution.Here we present a robust methodology for detecting abrupt
transitions in proxy records that is applied to a set of ice core,
speleothem, and marine sediment records of the last climate cycle and
the Holocene. This methodology is based on the nonparametric
Kolmogorov-Smirnov (KS) test for the equality, or not, of the
probability distributions associated with two samples drawn from a time
series, before and after any potential jump. The KS test is augmented by
several other criteria and it is evaluated against other jump detection
algorithms, aiming to establish a “gold standard” for
abrupt-transition detection. This objective approach to identifying
climate TPs will allow us to construct better nonlinear and stochastic
models of bifurcations in the Earth’s climate and its interactions with
ecosystems within the TiPES (Tipping Points in the Earth System)
EU-funded project.