A terrifying glimpse into Earth’s future: Scientists simulate a ‘runaway greenhouse effect’

From Armageddon to the Day After Tomorrow, there have been plenty of Hollywood movies about how our world might end.

Now, a study has provided a terrifying glimpse into our planet’s future, and it doesn’t look pretty. 

Researchers have simulated a ‘runaway greenhouse effect’ – a dramatic escalation in temperatures on our planet.

Worryingly, they say that Earth could soon be an ‘uninhabitable hell’, much like our neighbouring planet, Venus.

And we don’t have to look too far into the future to reach that point, with scientists predicting a runaway greenhouse effect on Earth could only be a couple of hundred years away or even sooner.

The new study was led by astronomers at the University of Geneva (UNIGE), along with France’s CNRS laboratories in Paris and Bordeaux. 

They warn of the ‘evaporation of the entire surface ocean’ of Earth and a ‘dramatic increase in global surface temperatures’. 

‘This climatically unstable transition separates two population of planets – temperate planets and hot post-runaway planets,’ they say in their paper.

‘This is one of several scenarios that are meant to explain the difference between the Earth and early-Venus.

‘The understanding of the runaway greenhouse is pivotal to assess the different evolution of Venus and the Earth.’ 

Venus is known as Earth’s ‘evil twin’ because its also rocky and about the same size, but its average surface temperature is a blistering 870°F (465°C). 

Thanks to its dense atmosphere, Venus is even hotter than planet Mercury, even though the latter orbits closer to the sun.

The rocky sphere is not only inhospitable but also sterile – with a surface hot enough to melt lead and toxic clouds of sulfuric acid. 

Even from Earth, Venus is the brightest thing in the night’s sky apart from the moon, and can be discerned by a slight yellowish tint. 

In this way, it acts as a visible warning to Earthlings of what can happen to a planet. 

Although gases like carbon dioxide and methane are renowned for causing global warming, the study authors say a runaway greenhouse effect on Earth could really be triggered by water vapour. 

The world is already warming due to emissions of carbon dioxide and methane, and this results in more water vapour in the atmosphere, due to the evaporation of the oceans. 

And although many people don’t know it, water vapour is a natural greenhouse gas. 

Water vapour prevents the solar radiation absorbed by Earth to be reemitted towards the void of space, because it traps heat ‘like a rescue blanket’. 

The greenhouse effect further increases the evaporation of oceans, and in turn further fuels the amount of water vapour in the atmosphere – a catastrophic, rapidly-escalating spiral. 

‘There is a critical threshold for this amount of water vapour, beyond which the planet cannot cool down anymore,’ said lead author Guillaume Chaverot at the UNIGE. 

‘From there, everything gets carried away until the oceans end up getting fully evaporated and the temperature reaches several hundred degrees.’ 

With new climate models, the scientists calculated that a very small increase of radiation from the sun would lead to an increase of the global Earth temperature, of only a few tens of degrees.

This would be enough to trigger this irreversible runaway process on Earth and make our planet as inhospitable as Venus, they claim.

Researchers have outlined the three-part process, which they say could be applied to any planet with oceans, even those outside our solar system (known as exoplanets). 

First, assuming initially a liquid surface ocean, there is an evaporation phase, which enriches the atmosphere with water vapour. 

Second, when the ocean is considered to be entirely evaporated, there is a ‘dry transition phase’ during which the surface temperature increases dramatically.

Finally, the evolution ends with a hot and stable ‘post-runaway state’, which is what Venus has been in for the last 700 million-odd years, experts estimate. 

The team’s research also highlights why information about an exoplanet’s temperature, as determined by satellites and powerful telescopes, is key to identifying where aliens are outside our solar system. 

If an exoplanet is too hot, it is likely to have conditions akin to Venus and be less of a contender for harboring life. 

‘By studying the climate on other planets, one of our strongest motivations is to determine their potential to host life,’ said study author Émeline Bolmont at UNIGE.  

The results have been published in the journal Astronomy & Astrophysics.