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.

Runaway greenhouse effect can transform a temperate habitable planet with surface liquid water ocean into a hot steam dominated planet hostile to any life (artist’s depiction)
Today, Venus is the warmest planet in the solar system, with a surface hot enough to melt lead and a thick atmosphere containing toxic clouds of sulfuric acid

What is the runaway greenhouse effect?

The ultimate climate emergency is a ‘runaway greenhouse effect’ – a dramatic, snowballing rise in global temperatures. 

It’s where a hot and water-vapour-rich atmosphere limits the emission of thermal radiation to space.

This prevents the planet from cooling and from having liquid water on its surface, causing escalated global warming. 

Source: The Royal Society  

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. 

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

READ MORE The world is on track for a ‘hellish’ 3°C of global warming 

Scientists think the world could pass several catastrophic points of no return

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 think the evaporation of Earth’s oceans will mark ‘a runaway greenhouse effect’ by trapping more heat from the sun. That’s because water vapour is a natural greenhouse gas
Too much greenhouse effect increases the evaporation of oceans, and thus the amount of water vapour – a natural greenhouse gas – in the atmosphere (depicted here in the team’s calculations)
A planet can evolve from a temperate state like on Earth to a true hell according to researchers (artist’s depiction). Earth is not so far from this apocalyptical scenario

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

Runaway warming could push the world into a ‘hothouse Earth’ state and cause sea levels to rise by almost 200 FEET in just a matter of decades, study warns 

Earth may be decades away from a climatic tipping point that triggers runaway global warming and threatens the future of humanity, scientists have warned.

The threshold will be reached when average global temperatures are only around 2C higher than they were in pre-industrial times, new research suggests. They are already 1C higher, and rising.

Feedback mechanisms acting ‘like a row of dominoes’ will then spin the world into a ‘Hothouse Earth’ state of uncontrollable climate change.

Long term, the Hothouse Earth climate will stabilize at a global average of 4C-5C above pre-industrial levels, the study shows.

Read more 

Reference

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