Is climate change time reversible?

TL;DR

This paper investigates the concept of time reversibility in climate data, proposing methods to detect irreversibility and linking it to environmental tipping points, with implications for climate policy urgency.

Contribution

It introduces a novel approach to detect time irreversibility in climate indicators using mixed causal models and trend filtering, connecting statistical properties to environmental tipping points.

Findings

Evidence of time irreversibility in GHG emissions and temperature.

Identification of irreversibility in sea levels and sea ice area.

Implication for urgent climate policy actions.

Abstract

This paper proposes strategies to detect time reversibility in stationary stochastic processes by using the properties of mixed causal and noncausal models. It shows that they can also be used for non-stationary processes when the trend component is computed with the Hodrick-Prescott filter rendering a time-reversible closed-form solution. This paper also links the concept of an environmental tipping point to the statistical property of time irreversibility and assesses fourteen climate indicators. We find evidence of time irreversibility in $GHG$ emissions, global temperature, global sea levels, sea ice area, and some natural oscillation indices. While not conclusive, our findings urge the implementation of correction policies to avoid the worst consequences of climate change and not miss the opportunity window, which might still be available, despite closing quickly.