Climate Stability of Habitable Earth-like Planets

TL;DR

This paper investigates how the carbon-silicate cycle affects climate stability on Earth-like planets, revealing that planets with less sunlight may experience unstable climate cycles, impacting the search for extraterrestrial life.

Contribution

It demonstrates that reduced insolation can lead to climate oscillations on Earth-like planets due to limitations in the carbon-silicate cycle feedback mechanism.

Findings

Planets with less sunlight may cycle between glaciated and warm states.

The carbon-silicate cycle's effectiveness depends on planetary insolation.

Climate stability is compromised on planets with insufficient sunlight.

Abstract

The carbon-silicate cycle regulates the atmospheric $CO_2$ content of terrestrial planets on geological timescales through a balance between the rates of $CO_2$ volcanic outgassing and planetary intake from rock weathering. It is thought to act as an efficient climatic thermostat on Earth and, by extension, on other habitable planets. If, however, the weathering rate increases with the atmospheric $CO_2$ content, as expected on planets lacking land vascular plants, the carbon-silicate cycle feedback can become severely limited. Here we show that Earth-like planets receiving less sunlight than current Earth may no longer possess a stable warm climate but instead repeatedly cycle between unstable glaciated and deglaciated climatic states. This has implications for the search for life on exoplanets in the habitable zone of nearby stars.