Research unveils atmospheric dynamics of runaway greenhouse effect

Research unveils atmospheric dynamics of runaway greenhouse effect
by Robert Schreiber
Geneva, Switzerland (SPX) Dec 19, 2023

A recent study by a team of astronomers from the University of Geneva (UNIGE), in collaboration with CNRS laboratories in Paris and Bordeaux, has successfully simulated the entire runaway greenhouse process, marking a significant advancement in understanding planetary climates. This process, which can dramatically transform a planet's climate from conducive to life to extremely hostile, has been a subject of intense study in climatology and astronomy.

Guillaume Chaverot, a former postdoctoral scholar at the UNIGE Faculty of Science, and the main author of the study, elucidates, "A global average temperature rise of just a few tens of degrees, following a slight increase in the Sun's luminosity, could initiate this phenomenon on Earth, making our planet uninhabitable." This statement underscores the delicate balance of Earth's climate and the potential risks posed by even minor changes in solar irradiation.

The study, published in Astronomy and Astrophysics, represents a world-first in climate modeling. It focuses on the transition period of the runaway greenhouse effect, examining how a planet's atmospheric structure and cloud coverage undergo significant changes during this critical phase. Martin Turbet, a researcher at CNRS and co-author of the study, emphasizes the novelty of their approach, stating, "It is the first time a team has studied the transition itself with a 3D global climate model, and has checked how the climate and the atmosphere evolve during that process."

One of the study's key findings is the development of a unique cloud pattern that exacerbates the runaway effect, making it nearly irreversible. Chaverot points out, "From the start of the transition, we observe dense clouds developing in the high atmosphere, altering the typical temperature inversion characteristic of the Earth's atmosphere."

This research has significant implications for the study of exoplanets, planets orbiting stars other than the Sun. Emeline Bolmont, assistant professor and director of the UNIGE Life in the Universe Center (LUC), and a co-author of the study, highlights the relevance of these findings for the quest to identify exoplanets with potential to host life. The study not only confirmed the existence of a critical water vapor threshold but also discovered a cloud pattern that could serve as a detectable signature in exoplanet atmospheres.

Furthermore, the team is committed to advancing this research. Chaverot, who has received a research grant to continue the study at the Institut de Planetologie et d'Astrophysique de Grenoble (IPAG), plans to focus on Earth's specific case in this ongoing project.

The results of their climate models indicate that a minor increase in solar irradiation, causing a global temperature rise of a few tens of degrees, could trigger an irreversible runaway process on Earth, akin to conditions on Venus. Chaverot warns, "If this runaway process starts on Earth, an evaporation of just 10 meters of the oceans' surface would dramatically increase atmospheric pressure and temperature, eventually reaching over 1,500CC with all oceans evaporated."

Research Report:First exploration of the runaway greenhouse transition with a 3D General Circulation Model