A stable hothouse triggered by a tipping mechanism

TL;DR

This paper introduces a new temperature-carbon-vegetation model revealing a novel climate tipping mechanism that can trigger a stable hothouse Earth state under high emissions, aligning with observed and modeled climate behaviors.

Contribution

The paper presents a coupled TCV model demonstrating a previously uncharacterized climate tipping mechanism leading to a stable hothouse Earth state.

Findings

Identification of a new climate tipping mechanism involving temperature-albedo feedback and vegetation limits.

Model simulations match observed climate behavior prior to tipping points.

The mechanism explains potential irreversible climate shifts under high emissions.

Abstract

The climate system's nonlinear dynamics is influenced by various external forcings and internal feedbacks that can give rise to regional and even global tipping points that may lead to significant and potentially irreversible changes. Paleoclimatic records reveal that Earth's climate has shifted between distinct equlibria, including a "hothouse Earth" state with temperatures about 10 K higher than present. However, a specific mechanism for a sudden tipping to an alternate stable state, several degrees warmer than the present climate, has yet to be presented. We introduce a temperature-carbon-vegetation (TCV) model comprising an energy balance model of global temperature, coupled with global terrestrial and ocean CO2 dynamics, and with vegetation ecosystem change. Our model exhibits a new tipping mechanism that leads to a hothouse Earth under a high-emissions scenario. Its simulations align with both observations and IPCC-class global climate models prior to tipping. The two processes that produce global tipping are: (i) temperature-albedo feedback due to darkening of the terrestrial cryosphere by glacial microalgae; and (ii) limits to vegetation adaptation that lead to reduced carbon absorption.