Local /finite-time Lyapunov exponents as early warning signals

[Datseris]

Indicator summary

Abrupt climate change has an important impact on sustainable economic and social development, as well as ecosystem.
However, it is very difficult to predict abrupt climate changes because the climate system is a complex and nonlinear system.
In the present paper, the nonlinear local Lyapunov exponent (NLLE) is proposed as a new early warning signal for
an abrupt climate change. The performance of NLLE as an early warning signal is first verified by those simulated abrupt
changes based on four folding models. That is, NLLE in all experiments showed an almost monotonous increasing trend as
a dynamic system approached its tipping point. For a well-studied abrupt climate change in North Pacific in 1976/1977, it
is also found that NLLE shows an almost monotonous increasing trend since 1970 which give up to 6 years warning before
the abrupt climate change. The limit of the predictability for a nonlinear dynamic system can be quantitatively estimated by
NLLE, and lager NLLE of the system means less predictability. Therefore, the decreasing predictability may be an effective
precursor indicator for abrupt climate change

Reference

Climate Dynamics (2021) 56:3899–3908
https://doi.org/10.1007/s00382-021-05676-1
Decreasing predictability as a precursor indicator for abrupt climate
change
Wenping He et al

Implementation plan

To be discussed. Local/nonlinear/finite-time Lyapunov Exponents are implemented in ChaosTools.jl but for analytic dynamical systems, not timeseries....