We quote the last part of this Phys.org article, headed: ‘A planet Earth in a fragile equilibrium.’ Somehow the model finds that once the oceans have eventually evaporated ‘we would even reach 273 bars of surface pressure and over 1,500°C’. This seems a bit unlikely on the face of it as it’s three times the surface pressure, and temperature [note the link between those two] of Venus despite being nearly 40% further away from the Sun. We note that it’s not unheard of for climate models to over-predict temperature effects.
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Talkshop note – the article earlier states:
One of the key points of the study describes the appearance of a very peculiar cloud pattern, increasing the runaway effect, and making the process irreversible. “From the start of the transition, we can observe some very dense clouds developing in the high atmosphere. Actually, the latter does not display anymore the temperature inversion characteristic of the Earth atmosphere and separating its two main layers: the troposphere and the stratosphere. The structure of the atmosphere is deeply altered,” says Chaverot.
. . .
A planet Earth in a fragile equilibrium.
With their new climate models, the scientists have calculated that a very small increase of the solar irradiation—leading to an increase of the global Earth temperature, of only a few tens of degrees—would be enough to trigger this irreversible runaway process on Earth and make our planet as inhospitable as Venus.
One of the current climate goals is to limit global warming on Earth, induced by greenhouse gases, to only 1.5° by 2050.
One of the questions of Chaverot’s research grant is to determine if greenhouse gases can trigger the runaway process as a slight increase of the sun luminosity might do.
If so, the next question will be to determine if the threshold temperatures are the same for both processes.
The Earth is thus not so far from this apocalyptical scenario.
“Assuming this runaway process would be started on Earth, an evaporation of only 10 meters of the oceans’ surface would lead to a 1 bar increase of the atmospheric pressure at ground level. In just a few hundred years, we would reach a ground temperature of over 500°C. Later, we would even reach 273 bars of surface pressure and over 1,500°C, when all of the oceans would end up totally evaporated,” concludes Chaverot.
Full article here.
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From the research article:
The key process allowing a runaway greenhouse is the evaporation of the surface ocean. To model the ocean, we used a two-layer slab ocean without heat transport, coupled to the atmosphere (see Sect. 2.2). Evaporating the totality of the Earth’s oceans will induce a vapor surface pressure of 273 bar. Regarding the large heat capacity of the water vapor, any temperature modification will be extremely slow in this situation, making such a simulation unachievable from a numerical point of view. Moreover, the timescale required to evaporate enough water to reach this pressure are also hugely long. [bold added]
First exploration of the runaway greenhouse transition with a 3D General Circulation Model (2023)
Tallbloke's Talkshop 
Researchers: ‘The key process allowing a runaway greenhouse is the evaporation of the surface ocean.’
https://www.aanda.org/articles/aa/full_html/2023/12/aa46936-23/aa46936-23.html#S2
Not CO2.
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Wikipedia: ‘the atmospheric pressure and temperature at about 50 km to 65 km above the surface of the planet is nearly the same as that of the Earth, making its upper atmosphere the most Earth-like area in the Solar System.’
https://en.wikipedia.org/wiki/Atmosphere_of_Venus
‘the most Earth-like’ despite 96% CO2.
“only a few tens of degrees”
Haha! So they’re contemplating globally averaged warming of “only” 30-40°C, compared to our best estimate of total global warming to date since the late Little Ice Age of about 1.2±0.2 °C. Hilarious!
Amusingly, the phys dot org article says:
“On Earth, a global average temperature rise of just a few tens of degrees, subsequent to a slight rise of the sun’s luminosity, would be sufficient to initiate this phenomenon and to make our planet inhabitable.”
Enquiring minds want to know: “inhabitable by what?”
I think their time would be better spent looking for the bug in the program.
Ah, they are trying out a new computer game but they obviously messed up the programming because it doesn’t work.
The big question is – how much is this game play costing the public? Another question is – who let them play stupid games on the big computer when they obviously don’t know what they are doing?
One has to question the amount of education these so called climate scientists have – it sounds very like primary school only but I have to admit they have cottoned on to the money making scam very quickly. The standard of STEM education needs to be raised to what it was in the 50s not what it is now where everyone must have prizes.
“we used a two-layer slab ocean without heat transport…
Thus ignoring more laws of physics than you could shake a stick at…
How does this crap ever get published?
Evaporating the totality of the Earth’s oceans will induce a vapor surface pressure of 273 bar.
Massively increasing the surface pressure of a planet, for whatever reason, will massively increase the temperature. That has nothing to do with radiation.
Did they notice that their final pressure and temperature figures were both over 3* those on Venus?
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They seem to admit that CO2 has little effect overall…
We show that even if the tipping point of the runaway greenhouse depends on the simulation setup (e.g., continents, with CO2 as a minor constituent), the evolution path during the transition does not, for a given background gas pressure. As the bottom part of the atmosphere is water-dominated, it becomes optically thick and the physics is decoupled from the surface conditions. In the same way, a low content of CO2 (376 ppm) does not influence the climate beyond the onset (Fig. 1).
“Regarding the large heat capacity of the water vapor, any temperature modification will be extremely slow in this situation, making such a simulation unachievable from a numerical point of view.”
Authors must be very progressive, unencumbered with any knowledge of modeling.
Due to the strong opacity of water in the infrared, the thermal emission can be fully absorbed by the atmosphere when the temperature is high enough. Consequently, the thermal emission reaches a maximum, named the Simpson-Nakajima limit.
https://www.aanda.org/articles/aa/full_html/2022/02/aa42286-21/aa42286-21.html#S1
Above that limit ‘the planet enters a runaway greenhouse state’. But the Earth has survived many extremes…
…carbon dioxide is not anywhere near as effective at blocking outgoing longwave radiation as water is.
. . .
…during 80% of the latest 500 million years, the Earth is believed to have been in a greenhouse state due to the greenhouse effect, when there were no continental glaciers on the planet, the levels of carbon dioxide and other greenhouse gases (such as water vapor and methane) were high, and sea surface temperatures (SSTs) ranged from 40 °C (104 °F) in the tropics to 16 °C (65 °F) in the polar regions. [bold added]
https://en.wikipedia.org/wiki/Runaway_greenhouse_effect#Earth
Wikipedia misdirection: ‘levels of carbon dioxide and other greenhouse gases’ should read: ‘levels of water vapour and other greenhouse gases’ such as… [etc].
Water vapour is easily the important factor. Once all the water has gone (Venus) the carbon cycle ‘which requires precipitation to function’ fades away, so CO2 remains in the atmosphere and then takes over. That’s a result of the process, not the cause of it.
Solar Radiation.Yes, all that water vapour in the atmosphere BLOCKING the Solar Radiation from reaching the Oceans below the clouds. They obviously don’t know that LWIR makes up a very small percentage of Solar Radiation.
Raising the water vapour content of the atmosphere necessarily increases the planetary cloud albedo – Negative feedback response.
Raising the surface atmospheric pressure necessarily increases the boiling point temperature of water. – Negative feedback response.
There are two things that dominate Earth’s climate:
1: Short wavelength Albedo
2: Long wavelength Atmospheric Window.
The Application of the Dynamic Atmosphere Energy Transport Climate Model (DAET) to Earth’s Semi-Opaque Troposphere
So despite needing a ‘hugely long timescale’ to invoke ‘the runaway process’, the article asserts that ‘The Earth is thus not so far from this apocalyptical scenario’.
Does not compute 🤪
This paper (https://www.aanda.org/articles/aa/full_html/2023/12/aa46936-23/aa46936-23.html) is simply a model-generated JUNK, because the “runaway greenhouse” concept represents the most egregious violation of the Energy Conservation Law (a.k.a. the First Law of Thermodynamics) done in a mathematical model.
All climate models (GCMs) violate Energy Conservation due to improper & artificial decoupling of radiative transfer from convective heat transport in the code of these models. Scientists call the result of this a CO2-dependent climate sensitivity! The “runaway greenhouse” is just an extreme example of such a violation.
One can easily understand the problem by realizing that positive feedbacks simulated by models between surface temperature and atmospheric water vapor cause the system to increase its internal kinetic energy through rising the IR opacity of air and without the involvement of any diabatic or adiabatic heating mechanism. This makes the “runaway greenhouse” physically nonsensical!
If you can’t quantify and measure it it you don’t understand it, and cannot predict it, so are making it up. YOu are are climate scientist, not a real scientist.
So here are some engineer’s numbers we have measured and do know, how they vary hence some more probable science that applies both these criteria..
AS already pointed out here, the evaporative negative feedback that cools the surface is 86.4W/m^2 average latent heat of water vapour convected to the Troposphere adiabatically, per NASA 10 year assessment. That MUST vary by 7% per degree K SST across a wide range of temperature and RHI. THat evaporation produces those Tropospheric clouds by convective adiabatic transfer and condensation of the water vapour to the Troposphere that reflect 50W/m^2 of incoming EMR on average at 288 K average SST, which we can assume has similar increase per deg K hence a combined significant net effect ( after the insulation of the ocean surface at night effect is subtracted ). THis is in addition to the S-B radiative effect, of roughly 1% per deg K at (299/298)^4 so 2.4W/m^2 per deg K, either from the solid or liquid surface, or the TOA when scattering occurs. Even allowing for an extra radiative perturbation by increased water vapour GHE of 2W/m^2 per deg SST that NASA assesses it at , the net negative feedback must self evidently be close to 10W/m^2 per deg. Warming or cooling.
So the 1.6W/M2 of human AGW is balanced by an SST increase of 0.16deg K. Most recent warming change we see is thus most likely to be the typical and timely natural cycles of the the geological record from multiple sites around the World.
None of this needs a model, it needs real scientists who can work with facts and physics and definite theories, rather than make it up in models theu program wit their own guesses. We have the data and the phsyical laws to do the macro level assessments on the response of whole planet heat balance to perturbations from whatever cause. THis immediately scales the problem and shows just how strongly controlled the energy balance within the solar system environment is, with a net 10W/m^2 average negative feedback per deg available to rebalance any perturbation to the system.
JUst is. How can it be significantly different? Basic phsyics 101. No models required. The detail internalss may be tricky, but the whole system macro level balance and the dominant causes and effects are self evident.
If you disagree, please provide a clear explanation why…. which is always welcome, as welcome as baseless gibberish based on guesswork or assertion is not.
nb Contains no models. Your climate may vary. Changes may be smaller than they appear in the models.
PS Venus has no magnetic field and is half-way to the Sun from Earth, so receives 4 times the average solar energy Earth does, c. 1,360W/m^2. On Earth about half the 340W/m^2 average solar enrgy 160W/m^2 gets to the surface. To offset the additional 1,200W/m^2 at the ocean surface at 10W/m^2 per degree would require the SST to increase by 120 degrees, if the water could without boiling at 388K and the curve was linear. etc. All irrelevant as they would certainly boil off entirely. Thermal equilibrium needs to boil off all the water and raise the S-B temperature a lot, a much less sensitive control
But Venus is not Earth, comparisons are pointless as this quick test shows, and models are fairy tales made up by their programmers. Not real science. The nearest equivalent to Earth appears to be the similar but much colder thermal equilibrium of Jupiter;s Moon Titan, which has liquid methane oceans, Methane vapour, clouds and ice, and also a tropopause in the methane atmosphere at the same 0.1 Bar that exists on all atmopsheric planets with atmospheres observed so far, so clearly a natural thermodynamic effect. But Titan is not Earth either. CEng, CPhys…
so the grifters built a new Play Station climate game to terrorize the rubes with… *spit* What a farce.
https://th.bing.com/th/id/R.4f206a61e66b70945c3a7b548ef3b508?rik=Cyjt8Eu245byJg&riu=http%3a%2f%2fbenwilliamslibrary.com%2fblog%2fwp-content%2fuploads%2f2013%2f11%2fIce-Ship.jpeg&ehk=qMZooJwPJL4hwhKfArsxs467%2bbQv7rkNmKBDHBicDRs%3d&risl=&pid=ImgRaw&r=0
Wow! another damn model! Shall we run scared as hell to our government demanding something be done immediately? Not me I’m throwing another log on the fire and sipping a little wine!
beyondtronic
Seems you have a good time. While sipping your wine you may have a look at this paper: https://doi.org/10.53234/SCC202304/05
Your worry about runaway GHE will go away…
Nothing to panic about there.
Oldbrew this is nice. But what about this:
The GE effect is not increasing with increasing CO2.