Status: 22.12.2023, 19:18 PM
By: Julian Mayr
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Astronomers at the University of Geneva have simulated the process of a self-reinforcing greenhouse effect for the first time. Its impact on the Earth would be devastating.
Geneva – The view of space has fascinated mankind for thousands of years. However, ever since the systematic observation and exploration of space, people have been asking themselves the question: What concrete benefits does space research have for us on Earth? A very concrete example of the benefit is, for example, a complex computer simulation developed by astronomers. With the help of these, it was recently possible to investigate the effect of a self-reinforcing greenhouse effect on planets – with threatening findings for the Earth.
From Livable to Hostile to Life: Study on Galloping Greenhouse Effect Simulates Process for the First Time
Earth and Venus could hardly be more different except for their size and mass. On the one hand, a blue planet, habitat for numerous species, on the other hand, a yellowish and inhospitable planet. But this was not always the case: Venus is also said to have had moderate temperatures for two billion years and even oceans. Only the occurrence of a so-called galloping greenhouse effect turned Venus into a hellish greenhouse with average temperatures of well over 400 degrees Celsius.
Galloping greenhouse effect
The galloping greenhouse effect is a self-reinforcing effect of the warming of an atmosphere. The phenomenon is not new and was described by researchers as early as 1970. As a planet's surface temperature rises, its liquid water reservoirs gradually evaporate. The gaseous water in the atmosphere then acts as a greenhouse gas. The water vapor prevents the solar radiation absorbed by the Earth from being reflected back into space as thermal radiation. This, in turn, leads to a further increase in temperature and the evaporation of more water. While a certain degree of greenhouse effect ensures moderate temperatures like on Earth, the galloping one continues to drive global warming.
Sources: Rasool/De Bergh (1970), Chaverot et al. (2023)
Now, for the first time, a team of researchers from the University of Geneva, with the support of the Centre national de la recherche scientifique (CNRS), has simulated the complete process of such a galloping greenhouse effect in Paris and Bordeaux. The results of the study, published in the journal Astronomy & Astrophysics, show how a planet's livable climate can dramatically turn into a hostile one.
Self-reinforcing greenhouse effect causes irreversible conditions
In the first-time simulation using the 3D General Circulation Model (GCM), for example, increased solar radiation and associated temperature rises can cause large parts of water to evaporate on the surface of a planet. The resulting water vapor in turn acts as a greenhouse gas, heating surface temperatures to more than 1000 degrees Celsius in a simulated final stage when a critical threshold of evaporated water in the atmosphere is exceeded, explains Guillaume Chaverot, one of the authors of the study.
The galloping greenhouse effect can turn a temperate planet into an inhospitable one. © Thibaut Roger
The scientists also showed that the structure of the atmosphere and cloud cover change so significantly in the first stages of the process that they almost inexorably bring the planet into an irreversible state. "From the very beginning, we can observe how very dense clouds develop in the upper atmosphere. The latter no longer has the temperature inversion typical of the Earth's atmosphere, which separates its two main layers, the troposphere and the stratosphere," explains Chaverot. As a result, the structure of the atmosphere is "profoundly changed."
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Galloping greenhouse effect on Earth: surface temperature of over 500 degrees is the result
The researchers calculated that a relatively small temperature increase of a few dozen degrees, triggered by an increase in solar radiation, for example, could be sufficient to trigger these irreversible processes on Earth as well. In the worst-case scenario, forecasts by the IPCC predict an increase in the global average temperature of five to six degrees. However, Chaverot's research team wants to clarify whether released greenhouse gases such as methane or CO₂ could also trigger a galloping greenhouse effect.
In just a few hundred years, we would have reached a soil temperature of over 500 degrees.
Guillaume Chaverot, astronomer and author of the study
If this were the case, the Earth could well be in danger of becoming uninhabitable in the foreseeable future: "Assuming that this uncontrollable process were set in motion on Earth, an evaporation of just ten meters of the ocean surface would lead to an increase in atmospheric pressure near the ground by one bar. In just a few hundred years, we would have reached a soil temperature of over 500 degrees," predicts Chaverot.
With the help of the new findings, the astronomers also hope to make progress in the study of exoplanets. "By studying the climate on other planets, we want to determine whether they could host life," says co-author Émeline Bolmont about the research group's work. For others, extraterrestrial life has long since arrived on Earth.