Study: “Venus was once more Earth-like, but climate change made it uninhabitable”

Guest essay by Eric Worrall

Despite the unsettling title, the authors are not trying to say Earth will end up like Venus if we don’t mend our wicked ways. But the Forbes article and study models positing an early ocean covered Venus appear to make a lot of assumptions, with very little evidence to guide those assumptions.

Venus was once more Earth-like, but climate change made it uninhabitable

December 14, 2020 12.04am AEDT
Richard Ernst
Scientist-in-Residence, Earth Sciences, Carleton University (also a professor at Tomsk State University, Russia), Carleton University

We can learn a lot about climate change from Venus, our sister planet. Venus currently has a surface temperature of 450℃ (the temperature of an oven’s self-cleaning cycle) and an atmosphere dominated by carbon dioxide (96 per cent) with a density 90 times that of Earth’s. 

Venus is a very strange place, totally uninhabitable, except perhaps in the clouds some 60 kilometres up where the recent discovery of phosphine may suggest floating microbial life. But the surface is totally inhospitable.

However, Venus once likely had an Earth-like climate. According to recent climate modelling, for much of its history Venus had surface temperatures similar to present day Earth. It likely also had oceans, rain, perhaps snow, maybe continents and plate tectonics, and even more speculatively, perhaps even surface life. 

Less than one billion years ago, the climate dramatically changed due to a runaway greenhouse effect. It can be speculated that an intensive period of volcanism pumped enough carbon dioxide into the atmosphere to cause this great climate change event that evaporated the oceans and caused the end of the water cycle.

Read more:

The abstract of the study;

Was Venus the first habitable world of our solar system?

M. J. Way, Anthony D. Del Genio, Nancy Y. Kiang, Linda E. Sohl, David H. Grinspoon, Igor Aleinov, Maxwell Kelley, Thomas Clune

Present‐day Venus is an inhospitable place with surface temperatures approaching 750 K and an atmosphere 90 times as thick as Earth’s. Billions of years ago the picture may have been very different. We have created a suite of 3‐D climate simulations using topographic data from the Magellan mission, solar spectral irradiance estimates for 2.9 and 0.715 Gya, present‐day Venus orbital parameters, an ocean volume consistent with current theory, and an atmospheric composition estimated for early Venus. Using these parameters we find that such a world could have had moderate temperatures if Venus had a prograde rotation period slower than ~16 Earth days, despite an incident solar flux 46–70% higher than Earth receives. At its current rotation period, Venus’s climate could have remained habitable until at least 0.715 Gya. These results demonstrate the role rotation and topography play in understanding the climatic history of Venus‐like exoplanets discovered in the present epoch.

Read more:

The assumptions behind this modelling exercise appear to be a significant stretch. For example;

Venus was resurfaced by volcanic activity hundreds of millions of years ago [e.g., McKinnon et al., 1997Kreslavsky et al., 2015], so its topography before that time is unknown. As an estimate with some observational basis, we use modern topographic data from the Venus Magellan mission via the PDS (Planetary Data System) archive (http://pds‐‐v‐rss‐5‐gravity‐l2‐v1/mg_5201) and fill the resurfaced lowlands with water.

Read more: Same link as above

The postulated periodic “resurfacing” Venus experiences is far more violent than any volcanic event ever known to have occurred on Earth. The basis of the resurfacing theory is the lack of impact craters on Venus. The estimated age of impact craters which have been observed suggests the entire surface of Venus was covered in lava or otherwise destroyed in a violent volcanic upheaval around 300 million years ago. It seems a big assumption that the previous surface topography of Venus was anything like the current topography.

What about initial atmospheric conditions? Here the models make another big assumption, that the initial atmospheric conditions of Venus resembled Earth.

… Given the fact that Venus shows substantial N2 in its atmosphere today and has few modern day sources or sinks (unlike Earth), we assume that an ancient Venus could have had a ~1 bar N2 atmosphere (1012.6 mb) in its early history. A modern Earth amount of CO2 and CH4 is also included (400 ppm, 1 ppm), given otherwise poor constraints on these gas concentrations. …

Read more:

Don’t get me wrong, speculative modelling is obviously an interesting intellectual exercise, and might be useful to explore model boundaries or limits. But I think it would be a big leap to believe that models which struggle to explain the current climate of the Earth can tell us anything meaningful about events which occurred hundreds of millions of years ago on another planet.

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December 20, 2020 6:08 pm

Is this what passes for “science” these days?

John Endicott
Reply to  ScarletMacaw
December 21, 2020 3:56 am

Sadly, yes it is

Flight Level
December 20, 2020 6:15 pm

Despite being significantly closer to sun than earth, is there evidence of venusian junkyards of SUV’s, jet liners, anything that’s supposed to doom earth ?

Otherwise it could simply mean that despite phenomenal efforts to purify their planet and recycle all traces of civilization in a globalized fierce climate control effort, venusians were still baked by the sun.

Reply to  Flight Level
December 21, 2020 6:44 am

It does seem that Venutians have reduced their “carbon footprint” to about 0, and still it’s too hot.

December 20, 2020 6:18 pm

This is a classic example of circular reasoning. We believe CO2 is the control knob. Venus has high CO2. Ergo runaway global warming killed venus. Finally, since Venus is a inferno, thus Earth will be too if CO2 isn’t immediately reduced to a level that stunts the growth of most plants on Earth.

The fact that the current temperatures on Earth are not outside of the historical noise bands is irrelevant as long as one accepts the “We believe …” part of the statement

John Endicott
Reply to  OweninGA
December 21, 2020 3:59 am

Funny thing: Venus has 96.5% CO2 atmosphere and is damn hot. So obviously it’s the CO2 what done it. Mars has 95.32% CO2 atmosphere and is damn cold. Why didn’t the CO2 do it there, or is it that last 1.18% that makes all the difference?

D. J. Hawkins
Reply to  John Endicott
December 21, 2020 5:37 am

Making spurious comparisons doesn’t do you any favors. Mass has a quality all it’s own. The pressure at the surface of Venus is about 1,350 psi. That of Mars is 0.095 psi. Just a little different, yah? Doing “greenhouse” calculations, it’s really the partial pressure of the gas you’re interested in, not the ppm or ppv; how many molecules are there per unit volume, not how many compared to any other gas.

Reply to  D. J. Hawkins
December 21, 2020 6:59 am

But that is what Hansen did when analyzing Venus vis-a-vis CO2. His reasoning boiled down to “it was the CO2 what done it”. (He actually took lots of words to mean basically that!)

Reply to  D. J. Hawkins
December 21, 2020 8:08 am

I think his point was that it was the climate alarmists who made those spurious comparisons. I know a very intelligent mathematician who said to me ‘don’t be silly Venus is almost 100% CO₂ and it’s damned hot and that proves climate change’.

I guess he got that from ‘New Scientist’

WHY is the pressure so high, on Venus? Never understood that.

Last edited 1 month ago by Leo Smith
John Endicott
Reply to  Leo Smith
December 21, 2020 8:55 am

Thank you Leo, spot on. See D.J., it is possible to comprehend the point when you try.

Robert of Texas
Reply to  Leo Smith
December 21, 2020 4:21 pm

The atmosphere of Venus is made up of more heavier gasses than on Earth, so the weight of the atmosphere can be higher even at hotter temperatures.

Many of the molecules are very stable and not shattered in the upper atmosphere by high energy light which is what happens to water. If a molecule (or free atom) is light enough it can gain escape velocity and be lost to the planet.

CO2 is both stable and heavy enough to retain. N2 is very stable and heavy enough to retain. Hydrogen containing molecules are measured in parts per million (some water, a little hydrogen-sulfide,etc.) because they can be shattered and the atoms can escape.

If you raise temperatures you can “cook out” additional gases from the rock, and if it’s a heavy enough gas it builds up.

John Endicott
Reply to  D. J. Hawkins
December 21, 2020 8:53 am

<I>Making spurious comparisons doesn’t do you any favors. </I>

Indeed, and being unable to comprehend the obvious point (that other posters easily did) does you absolutely none as well. Since you didn’t understand it, let me spell it out for you: It’s the Climate Alarmist that made the spurious comparison between Earth and Venus based solely on CO2., I’m showing the absurdity of that comparison by pointing out that nearly the same CO2 percentage gives completely different results between Mars and Venus with the obvious implication that clearly CO2 isn’t the driver “what done it” using the Alarmists own spurious reasoning. Try re-reading the post with your sarcasm-detector turned on, maybe you’ll have better luck in the comprehension department.

Reply to  D. J. Hawkins
December 21, 2020 10:31 am

So, running the numbers (I used to verify my own numbers) I get the following partial pressures for CO2:

Venus: 1302.75psi (96.5% @ 1350psi)
Mars: 0.09psi (95.32% @ 0.095psi
Earth: 0.00675psi (450ppm (0.045%) @ 15psi)

So if CO2 is the control knob, shouldn’t earth be much colder than mars?

Walter Sobchak
Reply to  D. J. Hawkins
December 21, 2020 6:18 pm

Clearly you don’t know anything about science. Settled science says that climate is a function solely of the CO2 concentration of the atmosphere. So Venus is hot. It is settled science. I don’t know what you are arguing about.

Reply to  D. J. Hawkins
December 22, 2020 4:23 am

Exactly. The concept of ” climate” it Venus doesn’t relate to Earth’s climate. There is no evidence of plate tectonics on Venus. Plate tectonics requires water. Water has likely always been scarce on Venue. The atmosphere of Venus implies that has never had significant life. The rotational speed, which is slow to the point it is nearly tidally locked, doesn’t help life or alife sustaining climate.

David Middleton
December 20, 2020 6:19 pm

Based on Climate modelling which means BS. What result do we want, now design the model to produce that result.Another scare story. The planet will be long dead from other things before this happens.

December 20, 2020 6:21 pm

If only Greta had been there 0.7 GYA.

December 20, 2020 6:25 pm

Venus has 224,000 times more CO2 than Earth. Not only does Venus have a FAR greater fraction of CO2 (96.5% vs. 0.04%) Venus has an atmosphere 93 times denser than on Earth. It’s the density that’s key, not CO2. The Earth has such little oil that if we burned it all it would be insufficient to raise the pressure of our atmosphere appreciably.
Venus’s atmosphere at the altitude where its atmospheric pressure is the same as it is on the surface of the Earth is nearly the same temperature as the surface of the Earth – this despite Venus having 96.5% CO2 vs. Earth’s 0.04% CO2.  That’s why you might have read about fanciful plans to float a human habitat high in the Venusian clouds.  What Venus actually proves is that CO2 isn’t all that effective at trapping heat.
How can this be, you say? It is because CO2 is a very, very weak greenhouse gas – it only has very minor IR absorption bands, and the absorption is logarithmic – every additional doubling of CO2 produces less effect than the last doubling.
Venus is hot for one reason and it has little to do with CO2. Venus is hot because Venus has a crushingly dense atmosphere. Venus would be just as hot (or hotter) if the Venusian atmosphere was pure water vapor.

Reply to  Meab
December 20, 2020 6:28 pm

Or pure N2, providing the same opaque cloud layer was present. Without its clouds insulating the solid surface from the cold of outer space, the surface of Venus would be a whole lot cooler.

Last edited 1 month ago by co2isnotevil
John Tillman
Reply to  Meab
December 20, 2020 7:31 pm

Venus is hot because it turns so slowly. It’s hotter than also slow Mercury because it has an atmosphere which keeps the dark side from cooling off during the long night.

Reply to  John Tillman
December 20, 2020 7:41 pm

The AVERAGE temperature is independent of the rotational speed. While a slower rotation makes the daytime warmer, it also makes the nighttime colder and relative to the temperature based on the AVERAGE emissions, they cancel.

On Venus, there’s little to no dirunal or seasonal temperature variability at the surface. This being the case, the rotational speed has no effect.

Reply to  co2isnotevil
December 20, 2020 11:10 pm

No, you are wrong. Emissivity changes with the fourth power of temperature. An isothermal body at temperature T emits less radiation than a body with half its surface at T+N and the other half at T-N, despite having the same average temperature The more isothermal, the less you emit and therefore the higher the temperature ends up being at equilibrium. Which is the opposite of what the previous commenter had said, so he is also wrong. Rotation affects average temperature because when the source of the heat is affecting only one side of the planet, the faster you rotate the more isothermal the planet is and the higher its average temperature becomes.

Take our moon, its temperature would be quite a lot higher if it was rotating faster (with minimum temperatures a lot higher but maximum temperatures quite smaller).

Reply to  Nylo
December 21, 2020 7:47 am

John T,

The local emissivity, relative to the surface temperature, is low (.4-.7) in the presence of clouds and high without (.8-.9). It’s average across the planet is remarkably constant at about 0.62. The emissivity of Venus. relative to its surface temperature is much, much lower, although the bulk of the energy arriving to and leaving from the planet is to and from its clouds, not the solid surface, as John points out.

Emissions are proportional to T^4, and are limited by the W/m^2 arriving at the surface which is the same as what leaves, regardless of the rotational speed.

Examine the evidence. The surface temperature of Venus is mostly constant from pole to pole, day to night and season to season. This is unambiguous data showing that neither the rotational speed or axial tilt has anything to do with its surface temperatur. Consider how sunlight affects the solid surface of Earth under the deep ocean, which like Venus is constant from pole to pole and lacks diurnal or seasonal variability.

The only way for the rotational speed to unify the temperature across the planet is if it rotates very fast, yet Venus does not. More evidence that it’s rotational speed has nothing to do with its AVERAGE surface temperature. This is because the clouds are blocking the DIRECT path from the Sun to the surface in both directions making the surface in thermal equilibrium with the clouds, not the Sun.

The average emissions of the Moon are equal to about 90% of the incident energy arriving from the Sun (307 W/m^2) corresponding to an AVERAGE temperature of about 271K, or about -2C. Since the rotation rate doesn’t affect the solar input, it can not affect the average emissions or average temperature. The W/m^2 emitted by higher daytime temperatures are completely offset by reduced W/m^2 emitted by lower night time temperatures.

The proper way to average the temperature is to average T^4 and not to calculate a linear average of T. Alternatively, T can be converted to W/m^2 with the SB Law, the W/m^2 are linearly averaged and the result converted back to a temperature. The IPCC’s emphasis on linearizing the relationship between W/m^2 and temperature is what confuses many as it implies that a linear average of T has some kind of physical relevance, which it does not.

John Tillman
Reply to  co2isnotevil
December 21, 2020 4:03 am

Venus’ slow rotation is the main reason for its temperature. Again, please compare with Mercury, which rotates less slowly than Venus but has practically no atmosphere. Its orbit is also more elliptical than Venus’.

The longer one spot on the surface is exposed to solar radiation, the hotter it gets. Mercury cools off at night, but Venus doesn’t, thanks to its dense atmosphere and high winds. Heat also travels through its lithosphere to the dark side.

There is no actual evidence that Venus was ever cool enough for water on its surface. It would have to have turned much more slowly than it now does, as the GIGO modelers admit.

Venus’ atmosphere actually shades the surface, thanks primarily to the high albedo of its SO2 clouds. At the top of its atmosphere, Venus gets twice as much sunshine as Earth, but only three percent makes it directly to the surface, and about another seven percent indirectly. Some 76% is reflected away, and the remaining roughly 14% absorbed by the oceanic-like air.

But with less radiation reaching its surface than on Earth, Venus gets much hotter because it turns so slowly and doesn’t doesn’t lose surface heat at night as rapidly as does Earth’s much thinner atmosphere.

Reply to  John Tillman
December 21, 2020 8:52 am

John T,

Consider a planet with no atmosphere whose average night time temp is 100K (5.67 W/m^2) and average day time temp is 300K (459.27 W/m^2). The Sun is delivering an average of (5.67 + 459.27)/2 = 232.37 W^2 corresponding to an average temperature of 253K.

What’s the average surface temperature? It’s not 200K, but 253K since with no atmosphere, the average surface temperature must be consistent with the average temperature of the incident radiation. You can calculate this from the average night and day temperatures as follows,

((100^4) + 300^4)/2)^0.25 = 253K

So yes, as the rotation rate changes, the linear average will change (move 50 W/m^2 of emissions from day to night to see how), but a linear average has no relevance to the physical average. The average surface temperature must always be the same as the average temperature of the incident solar energy, regardless of the rotation rate, in order for the averages to have any kind of physical significance.

Reply to  John Tillman
December 21, 2020 7:30 am

Can anyone point me to a straightforward hypothesis that explains Venus’ retrograde rotation? That just seems so difficult to reconcile with the “planets condensed from the disk of Solar System material” model – especially with no Venusian moon

Reply to  GeologyJim
December 21, 2020 9:10 am

My hypothesis is that it started life as a small gas giant in the outer solar system and collided with Uranus (which also as a retrograde rotation) moving it to the inner solar system and leaving it with its own retrograde rotation. Most of its atmosphere was blown away by the solar wind, leaving the heavier CO2 behind, much like how we think super Earth exoplanets arose. Earth could have even scavanged some of these gases contributing to our relative abundance of N2 and H2O.

Reply to  co2isnotevil
December 21, 2020 11:30 am

If Uranus and Venus had collided the result would have been either an asteroid field in the orbit of Uranus, or a existing planet about the size of Uranus and the previous Venus combined.

Planets are not like marbles that bounce when the crash into each other. The result is always the total destruction of both. Depending on the speed and angle of the collision, the debris either re-coalesces in about the same spot, or the debris is scattered and settles down into pretty much the original orbit.

Water vapor is a lot lighter than CO2, yet there is much more water vapor in Venus’s atmosphere than there is CO2.

Reply to  MarkW
December 21, 2020 1:47 pm

That is how our moon came into being.

Reply to  JohnC
December 21, 2020 4:03 pm

That is the current best theory. According to the theory the body that struck the Earth was about the size of Mars, it was a glancing blow, it shattered both the Earth and the striking body. The blow was direct enough that the core of the striking body was captured by the Earth, while most of the crust material was thrown off into space. Much of it escaped the gravity of the Earth, but a small part was went into orbit around the Earth and eventually coalescing into the Moon.
Additionally the glancing blow also accelerated the rotation rate of the Earth, much of which has since been transferred to the Moon lifting it from a much closer orbit out to where it currently is.

An interesting fact that I learned recently is that if a moon orbits in the same direction as the planet rotates, it will be slowly flung out from the planet. On the other hand if it rotates in the opposite direction, it’s orbit will gradually decay until it crashes into the planet.

Last edited 1 month ago by MarkW
Reply to  MarkW
December 22, 2020 8:03 am

Not necessarily, Consider two gas giants in the same orbit. They will collide very slowly. Most of the energy in the collision will be in their respective rotations, and if one is significantly lighter than the other, that rotational energy can be converted into a linear trajectory for the lighter planet sending it, in this case, towards the inner solar system. It’s even possible that the solid surfaces of the 2 planets never even touch and that the entire interaction occurred within their dense atmospheres which would be more elastic than not.

As the proto Venus starts to spiral in to the Sun, the solar wind strips away much of its atmosphere, reducing the mass of the planet causing its orbit to expand until the Sun isn’t stripping away its atmosphere. That some water is left is not surprising, but if it was a gas giant in the past, it would have had far more than it has now.

Clearly, a collision/near miss is the most likely, if not the only, possibility for imparting a retrograde rotation. So, both Venus and Uranus have definitely been involved in past collisions. So the question becomes if they didn’t collide with each other, what did they each collide with?

Reply to  co2isnotevil
December 21, 2020 1:46 pm

Uranus also has an axial tilt of 98 degrees.

John Tillman
Reply to  GeologyJim
December 22, 2020 7:25 am

Venus probably didn’t form with its present slow retrograde rotation of 243 days. More likely, its rotation began as a fast prograde turning, with a period of several hours, akin to most planets in the Solar System. Venus is close enough to the Sun to experience significant gravitational tidal dissipation. It also has air dense enough to create thermally-driven atmospheric tides that produce a retrograde torque.

Venus’ present slow retrograde rotation is in equilibrium balance between gravitational tides trying tidally to lock the planet to the Sun, and atmospheric tides trying to spin it in a retrograde direction. In addition to maintaining this present day equilibrium, tides are also sufficient to account for evolution of Venus’s rotation from a primordial fast prograde direction to its current slow retrograde rotation.

Various alternative hypotheses have been proposed in the past to explain Venus’ retrograde rotation, such as collisions or its having originally formed that way.

An argument against the hypothesis of equilibrium between gravitational and atmospheric tides is that Venus’ retrograde rotation is measurably slowing down. It has slowed by about one part per million since it was first measured by satellites. However IMO, this observation just means that the processes which produced first slowing, then reversed rotation continues.

John Tillman
Reply to  John Tillman
December 22, 2020 10:22 am

Atmospheric pressure doesn’t determine temperature, Boyle’s Law notwithstanding.

Jupiter’s atmosphere is very cold at the pressure of Venus’ surface, ie 9100 kPa. This occurs above 50 km into the giant planet’s atmosphere, while Venus’ surface is around 30 km from ToA.

Reading off this graph, it appears to be around 120 K, ie ~-153 degrees C.

John Tillman
Reply to  John Tillman
December 22, 2020 10:22 am

comment image

Roger Taguchi
Reply to  Meab
December 20, 2020 8:22 pm

You are mostly correct: Venus’ surface is hot because of its crushingly dense atmosphere. The reason is that as atmospheric molecules move upward, their gravitational potential energy U = mgh decreases. If there is no heat added to or removed from these molecules (i.e. if the change is adiabatic), the average kinetic energy must decrease. For a linear molecule like N2, the heat content (enthalpy) per mole is H = 7RT/2, or 7kT/2 per molecule, where R is the Ideal Gas Constant and k is Boltzmann’s constant. From dU/dh = -dH/dh = -(dH/dT)(dT/dh) on using the Chain Rule for derivatives, we can derive dT/dh = -2mg/7k for the temperature profile of the atmosphere (the dry adiabatic lapse rate)

This explains why temperatures decrease while you go up a mountain on the Earth, or why Death Valley is so hot. CO2 is a linear molecule, so the temperature profile would be similar, except that at high temperatures the vibrational energy contribution to heat capacity at constant pressure means that Cp = dH/dT is a little higher than 7k/2. The main difference for Venus is that the atmosphere is about 5 times thicker (the pressure at 60 km is similar to that at the Earth’s surface). The dry adiabatic lapse rate for the Earth is -10 K/km (due to greenhouse gases and latent heats released on cloud formation, the actual lapse rate is -6.8 K/km).

Therefore we expect the temperature at 50 km on Venus to be about 500 K cooler than at the surface (in this crude approximation we have assumed the accelerations due to gravity on Venus and the Earth are the same, and the mass of CO2 and N2 are the same, rather than proportional to 44 and 28). You can substitute actual values for g and m to get more accurate numbers, but the physics must be understood. A drop of 500 K from the surface temperature means that the surface temperature of Venus cannot be around 15 Celsius (the Earth’s mean temperature), because that would mean a temperature at 50 km of -485 Celsius = -212 K, an impossibility. Rather, a temperature of 15 Celsius at 50 km on Venus means a surface temperature of 515 Celsius (approx.). This assumes the temperature profile of Venus’ atmosphere is that of an adiabatic lapse rate (no greenhouse effect).

Wait! CO2 is a greenhouse gas, so how can there be no significant greenhouse effect on Venus?
Rather than being a very weak absorber, when CO2 is so high on Venus, pressure broadening and Doppler broadening at high speeds/temperatures means that the lines/bands are so wide that practically every infrared (IR) frequency is saturated (completely absorbed). But Kirchhoff’s Law says that a good absorber is a good emitter (radio telescope dishes are optimal for both transmitting and receiving radio signals). 100% absorption means 100% emission quickly follows. The result is zero NET absorption, and the temperature profile remains close to that of the adiabatic lapse rate. Final emission of IR photons to outer space (necessary for energy balance) then comes from Planck black-body emission from the cloud tops (at 50-60 km or so), as well as from CO2 molecules where there are no clouds. And this comes from layers close to 15 Celsius, similar to that at the Earth’s surface. Because Venus is closer to the Sun than the Earth is, energy balance means that a higher effective temperature of emission is necessary (but remember that the effective emission temperature for the Earth is around 255 K = -18 Celsius).

Because N2 and O2 are non-polar diatomic molecules, they cannot and do not absorb or emit any significant amount of IR energy. But in the Earth’s atmosphere, they constitute 99% of dry air (about 1% is non-polar monatomic Ar) and can store kinetic energy obtained during non-radiative collisions with greenhouse gas molecules like CO2 and H2O (water vapour). So IR emitted from the 15 Celsius Earth’s solid and liquid surface CAN be net absorbed by CO2 or H2O, with some energy transferred to N2, O2 and Ar which cannot re-emit energy as IR. This is the true molecular explanation of the greenhouse effect, which shows up as a lower-than-adiabatic cooling with increased altitude (288 K to 220 K, or -68 K over 10 km, which means -6.8 K/km). The throttling of outgoing IR from the surface to outer space by greenhouse gases means that incoming Solar radiation will be absorbed and result in a slightly higher surface temperature until by the Stefan-Boltzmann T^4 law there is energy balance once again.

The presence of a few % of N2 in the atmosphere of Venus means that there will be a small greenhouse effect as energy is stored (as enthalpy, heat content) in non-radiating N2 molecules.
But basically, Carl Sagan was wrong in ascribing the high surface temperature on Venus to a “runaway greenhouse effect” due to the high CO2 content in the atmosphere of Venus. Hope this helps.

Reply to  Roger Taguchi
December 20, 2020 10:41 pm

Very interesting but over my head. But…
Is this….

”Kirchhoff’s Law says that a good absorber is a good emitter (radio telescope dishes are optimal for both transmitting and receiving radio signals). 100% absorption means 100% emission quickly follows. The result is zero NET absorption, and the temperature profile remains close to that of the adiabatic lapse rate.

….what is occuring on Earth in your opinion?

Last edited 1 month ago by Mike
Reply to  Mike
December 21, 2020 3:38 am


Reply to  Mike
December 21, 2020 11:33 am

The adiabatic rate is the limiter, it isn’t the driver.
The temperature at any given height in the atmosphere is based on the temperature at the bottom of the column. The temperature at a given point is based on the temperature at the bottom, minus the adiabatic rate. Any molecule that is above the temperature of the surrounding molecules will rise until it is in equilibrium. If it is cooler, it will sink.

John Tillman
Reply to  MarkW
December 22, 2020 8:03 am


It’s easy to show that slow rotation is primarily responsible for Venus’ high temperature. Its atmosphere is important, but not chiefly due its surface pressure.

Mercury’s orbit is eccentric, while Venus’ is nearly circular, but let’s use mean solar irradiance. On average, Mercury receives 3.77 times as much sunlight as Venus.

A simplifying assumption is that, had Venus effectively no atmosphere, like Mercury, surface albedos would be about the same..

Mercury completes one rotation in 59 Earth days. At once per 243 days, Venus spins 4.12 times more slowly.

Hence, under the albedo assumption and using average insolation, Venus’ lit side would get 1.09 times hotter than Mercury. But its dark side would have 4.12 times longer to radiate heat away, so would get cold. Hence, the atmosphere is mainly what makes both day and night sides almost equally hot. (There might also be some thermal transmission through the lithosphere, which differs between the planets.) However, it’s not mainly surface pressure from the dense air, but primarily its high winds aloft which transfer heat from the day to night side, while density and composition of the atmosphere also play a role in insulating the surface.

John Tillman
Reply to  John Tillman
December 22, 2020 9:15 am

Mercury’s day side reaches 430 degrees C, but, due to lack of atmosphere, its night side cools off to -180 C.

Venus OTOH, thanks to its dense air, stays about 460 degrees C on both the lit and dark sides, at the poles or equator. This equanimity (lack of latitudinal variation in T) owes in part to its slight axial tilt (rotational obliquity) compared to the more seasonal Earth.

Reply to  John Tillman
December 22, 2020 5:11 pm


“It’s easy to show that slow rotation is primarily responsible for Venus’ high temperature.”

You have claimed this, but have not shown it in any way shape or form. As I said, the daytime highs increase and nightime lows decrease. but the average remains the same. It is impossible to show how a slow rotation affects the AVERAGE temperature because it does not. Don’t forget that longer days are accompanied by longer nights.

Especially for Venus, whose constant temperature day/night season to season and pole to pole is demonstrable constant. Feel free to explain how a slow rotation rate explains this.

John Tillman
Reply to  co2isnotevil
December 24, 2020 11:47 am

As I said. Easy.

On Mercury, the night side cools off. On Venus it doesn’t.

John Tillman
Reply to  co2isnotevil
December 24, 2020 11:55 am

Atmospheric super rotation carries heat from lit to dark side at high speed:

Reply to  Roger Taguchi
December 21, 2020 7:47 am

Why, then, are Antarctic valleys colder? Are they merely less cold?

Roger Taguchi
Reply to  Hugh
December 21, 2020 11:32 am

Surface temperatures depend on latitude; the poles receive less Solar radiation than points on the Equator or tropics. During the long winter nights at the poles (that can last for months), loss of energy via IR radiation to outer space can be so fast that there can be a temperature inversion in the first several hundred metres from the surface.

Conduction from the atmosphere to the surface is very poor, convection cannot transfer heat stored in the daytime (summer) DOWNWARD to the surface, and heat transfer by IR radiation from hot-to-cold is not fast enough to maintain a linear temperature profile (lapse rate).

The fast-moving circular Southern Ocean isolates Antarctica, so the centrifuge effect does not produce warm winds moving radially toward the South Pole (in a centrifuge, denser material is driven to the outside, which means toward the Equator on the rotating Earth, but less dense material, i.e. warm air or water is driven toward the Poles. Combined with the Coriolis Effect which diverts flows to the right in the Northern Hemisphere, and towards the left in the Southern Hemisphere, we can understand the clockwise circulation of ocean currents in the Northern Pacific & Northern Atlantic Oceans, high and low pressure air masses, tornadoes in the flat central plains of North America, etc.).

Reply to  Roger Taguchi
December 21, 2020 10:23 am

Very good post, although too technical for most. I understand and agree with what you wrote but I taught thermodynamics at a major university for years. I have two minor comments. 1) Doppler and pressure broadening high in Venus’s atmosphere where the pressure and temperature are similar to that on Earth’s surface don’t have nearly as much effect as claimed. Why? Surface emitted IR in those absorpion bands doesn’t make it up that far. The IR all comes from re-radiated IR from lower layers of the atmosphere but the energy exchange from the lower layers is dominated by convection. 2) N2 does radiate and absorb solar energy, it’s not exactly zero in the far IR,. It’s also not zero in the visible. That’s why auroras look green, that’s N2. Not the greenhouse effect but it does radiate.

Roger Taguchi
Reply to  Meab
December 21, 2020 12:40 pm

(1) I agree that convection transfers heat vertically much more efficiently than radiation, particularly over dark solid surfaces in the daytime producing thermals. However, the linear temperature profiles (lapse rates) for the troposphere are consistent with the most probable distribution of a fixed amount of energy over a fixed number of air molecules, and that is to give each molecule, ON AVERAGE, equal amounts of energy.

The dry adiabatic lapse rate on Earth is consistent with dU/dh = -dH/dh; i.e. d(U+H)/dh= 0, so every molecule, on average, in a vertical column has the same total energy, consisting of gravitational potential + enthalpy (heat content).

When heat is injected via greenhouse gases or latent heats when clouds form, adding equal amounts of energy to each molecule, on average, means the slope of the temperature changes, but the profile is still linear. The reason is that delta H = Cp.(delta T), so that the same %change in H results in the same %change in T.

Achieving equilibrium/steady state takes time, however, so convection speeds the approach to equilibrium/steady state (radiation requires continual absorption followed by emission followed by absorption, etc., and the mean free path of photons is small – of the order of metres in the Earth’s atmosphere near the surface).

So you are right that an IR photon emitted from the surface does not make it to 50 km, let alone 10 km. But collisions between gas molecules continually produce excited state molecules; for example at 15 Celsius, collisions between air (N2 and O2) molecules and CO2 produce approx. 3% of CO2 molecules in the v=1 first vibrational excited state for bond-bending vibration. These are continually emitting 667 cm^-1 photons as they fall down to the v=0 vibrational ground state. Those photons can be absorbed by other CO2 molecules in the v=0 ground state, producing v=1 excited state molecules.
There is at any temperature an equilibrium: CO2 + 667 cm^-1 photon= CO2*, where the CO2* represents an excited molecule.

For the greenhouse effect, the solid and liquid surface of the Earth emit Planck black-body radiation at infrared (IR) frequencies, including some 667 cm^-1 photons which are absorbed by v=0 CO2 molecules, shifting the equilibrium to the right (producing more CO2* molecules). If the excess CO2* molecules simply re-emit 667 cm^-1, then there would be no greenhouse effect. It is the quenching of most of the CO2* molecules during inelastic collisions with N2, O2, and less probably Ar molecules that transfers the absorbed energy of the photons to non-emitting air molecules. That energy ends up as increased translational and rotational energy of the departing molecules, i.e. as heat. [The vibrational energy levels of N2 and O2 are too widely separated that excited states are not important at around 15 Celsius.]

I wrote MOST of the excess CO2 molecules are quenched. LeChatelier’s Principle says that when a stress is applied to a system at equilibrium, the equilibrium shifts in such a direction as to PARTIALLY relieve that stress. The stress was increased CO2* on absorption of an IR photon emitted from the surface. MOST of the excess CO2* is quenched, but not all. At the new equilibrium, there will be a slightly higher temperature, and therefore a slightly higher CO2* concentration given by the exp(-deltaH/RT) law. At 400 ppmv CO2, N2 and O2 molecules outnumber CO2 by a factor of 1,000,000:400 = 2500:1. Assuming equal molecular heat capacities at constant pressure, Cp = 7k/2, approx. 2500 times more heat will be stored in N2 and O2 than in CO2 molecules. This is why deniers of the greenhouse effect are wrong when they say that CO2 is in negligible concentration: most of the heat is stored in non-radiating molecules, not CO2.

But the equilibrium equation CO2 + 667 cm^-1 photon = CO2* also applies to every layer of the troposphere, even if the layers are fractions of a metre thick. Thousands of layers would be involved, but eventually (depending on the exact frequency), IR energy emitted by CO2* escapes to outer space from the upper atmosphere via photons that are NOT subsequently absorbed.

You correctly note that Venus has 224,000 times the CO2 concentration on Earth, so even at 50-60 km where temperatures and pressures resemble those at the Earth’s surface, the CO2 level on Venus is going to be huge. Thus the mean free path of the 667 cm^-1 photon will be considerably less than that on the Earth at 10 km, and line and bandwidths will be considerably wider.

(2) The green and red auroral lines are due to transitions of the neutral O atom (from the singlet S to the singlet D, and singlet D to triplet P states, respectively). [Reference: “Atomic Spectra and Atomic Structure” by Gerhard Herzberg, (Dover 1944); Herzberg deservedly won the 1971 Nobel Prize for Chemistry]. Neutral O atoms are formed by dissociation of O2 molecules high in the upper atmosphere, due to high energy UV photons from the Sun, and are of negligible concentration in the troposphere where the greenhouse effect is important. N2 molecules are colourless (liquid nitrogen too), meaning negligible absorption of visible radiation; liquid oxygen is pale blue, due to electronic transitions allowed since the ground electronic state is triplet (containing two unpaired electrons).

Since the amount of visible light emitted in the spectrum of a 288 K Planck blackbody is negligible, electronic transitions of N2 and O2 molecules are negligible and irrelevant for the greenhouse effect in the troposphere.

Reply to  Roger Taguchi
December 21, 2020 5:52 pm

I got it sideways, and I thank you for the correction. The green in an Aurora is caused by Oxygen, but the pinks, some reds (most is from oxygen), and some blues ARE caused by nitrogen. Look up “color of nitrogen discharge tube”. Look up “colors in an Aurora”. In any case, I don’t take issue with this not being a factor in greenhouse warming – after all that’s why I wrote (quote; “this isn’t the greenhouse effect”).

By the way, you wrote a lot of stuff, almost all correct, but most of it at best only tangential to the discussion and a bit not applicable to Venus’s atmosphere at all. It’s harder to be concise than verbose, but since few people will wade through unnecessary verbosity, the extra effort to distill your arguments to just the germaine parts is usually worth it. When you’re verbose it looks like you just did a copy from the Encyclopedia Britannica. Just friendly advice.

Dr. Meab

[please fix your mispelling of your email autofilling to avoid getting caught in spam filter-mod]

Reply to  Meab
December 21, 2020 12:55 pm

What’s key is the subsurface contribution.

Reply to  Zoe Phin
December 21, 2020 4:06 pm

Something like 0.01% of the total.

December 20, 2020 6:25 pm

What ever happened to constraining models by reality? There’s simply not enough carbon and oxygen on the planet for our atmosphere to become 90 bar of CO2, nor are we close enough to the Sun for so much water to evaporate that the planet would be covered from pole to pole by a layer of clouds nearly completely opaque to the incident solar energy. These are the necessary conditions for a Venus like climate to emerge and anyone who thinks a few hundred ppm of atmospheric CO2 can do the same thing needs to learn how to think properly.

Richard (the cynical one)
Reply to  co2isnotevil
December 20, 2020 6:59 pm

What’s this “learn how to think properly”? No! What is needed is more of a willing suspension of disbelief. Without that there would not be, could not be the necessary consensus herd mentality. Come on you lemmings! All together now!

Reply to  co2isnotevil
December 20, 2020 10:33 pm

What would the atmospheric mass be if all the stored carbonates on the planet were converted to CO2?

Reply to  Dnalor50
December 21, 2020 12:02 am

Earth’s atmosphere is 20% O2, therefore Earth could become 20% CO2 by adding a C to the O2. The 20% CO2 is denser and has same volume of 20%.
Earth crust has huge amount oxygen but it’s oxided with other elements.
So, order to make more than 20% CO2, you have somehow liberate the oxygen from the rock or from water {H2O}. One make a lot iron/steel from Iron oxide ores.
Of course that a lot CO2 in the ocean:
The oceans contain about 50 times more CO 2 than the atmosphere and 19 times more than the land biosphere.”
CO2 is .04 percent. Times 50 = 2% of atmosphere.
Which 1/10th of burning all the oxygen of Earth Atmosphere to make CO2.
It seems easiest way to get a lot CO2, is to import it from Venus.
Ie making stuff like space elevators and etc.

Reply to  gbaikie
December 21, 2020 3:24 am

The amount of CO2 sequestered in the form of carbonates is orders of magnitude greater than the CO2 stored in the sea, atmosphere, oil reserves, coal, calthrates etc. My point is that earths atmospheric mass must have been much greater at one time, before life fixed the bulk of CO2 in the form of carbonates. The ability of tectonic plate movement and volcanism to release the CO2 seems slow by comparison. Maybe at some future time a shortage of CO2 will be a problem given that life has a great capacity for CCS.

Reply to  Dnalor50
December 21, 2020 10:10 am

The Earth’s atmosphere was certainly more massive in the past, but as long as the atmosphere remained semi-transparent, rather than opaque to solar energy and surface emissions, Earth would not have been Venus like.

Reply to  gbaikie
December 21, 2020 11:43 am

The reason why there is so much oxygen forming oxides with other minerals is that photosynthesis freed the oxygen from the CO2 a billion years or so ago.

Reply to  co2isnotevil
December 21, 2020 11:35 am

Steven Hawkins believed that we could turn the Earth into Venus if we kept burning fossil fuels.

Just goes to show you how easy it is to fool smart people, when the subject is something outside their field.

Rory Forbes
Reply to  MarkW
December 21, 2020 12:25 pm

And yet, neither of Hawking’s colleagues, Eduard Teller and Freeman Dyson bought into the AGW fraud. Both were outspoken about the scientific over reach. Hawking’s advocacy was political, not scientific. He knew damned well that CO2 is not Earth’s temperature control knob.

John Tillman
Reply to  Rory Forbes
December 22, 2020 2:58 pm

Would like to see what yhou have on Teller, but Dyson most certainly did not buy into the CACA hoax.

Rory Forbes
Reply to  John Tillman
December 22, 2020 5:46 pm

Regardless of the long list of attacks by everyone Google could find, including wikipedia, Edward Teller did sign on to the Oregon Petition Project, probably for the same reason that Freeman Dyson was against climate hysteria. However one wants to slice the 97% “consensus” surveys … they don’t come close to a 31,500 signees on the petition if one ever chooses to appeal to either numbers or authority. I know that ad hominem is a favorite argument used by AGW true believers, but so far, that’s their only complaint against the petition.

Reply to  Rory Forbes
December 23, 2020 6:45 am

The one I always hear is “they’re not CLIMATE scientists”

Rory Forbes
Reply to  TonyG
December 23, 2020 9:35 am

Exactly, TonyG, “they’re not CLIMATE scientists” is one of the many ad hominems they use.Strangely they have no trouble with calling people like James Hansen or Phil Jones “climate scientists”. Jones did his PhD in hydrology..In the past, climate was always a minor interest associated with agronomy, geology and oceanography. Politics made it into a star.

Reply to  MarkW
December 21, 2020 12:46 pm

Or when they simply accept what they’re told and don’t bother looking into it.

Reply to  TonyG
December 21, 2020 5:35 pm

I have colleagues I will not discuss this with due to their having swallowed it without looking at it. When discussions do happen, they are surprised when I explain that I don’t believe the proposition has been shown to be correct. I would point out more that many things have shown to be counter to the theory, but I am not that close to retirement yet. Academia is not open minded about consensus science. In my colleagues’ defense, they are all pretty dedicated to following their data and have confidence that others do the same, so just assume that CliSci’s ducks are in a row.

December 20, 2020 6:30 pm

“Habitable” used pretty loosely, unlikely as it is to find habitants evolved to take advantage of those conditions. They propose that atmspheric temperature is the only factor required for development of life, while the only example we have of planetary habitation has entirely different conditions. Garbage in, garbage out.

December 20, 2020 6:38 pm

What would modelling show if the assumption instead was that earth in the past was the same as Venus is now?

Reply to  Kalsel3294
December 21, 2020 11:45 am

Over the first few million years, Earth was very likely quite similar to Venus. The difference was that as the heat of formation escaped, Earth was far enough from the sun for the water in the atmosphere to start condensing. Venus was too close and the water stayed in the atmosphere.

John Tillman
Reply to  MarkW
December 22, 2020 2:59 pm

And it rotated too slowly.

No one
December 20, 2020 6:56 pm

Models based on assumptions, not facts, are like graphs without legends.

Jeff Alberts
Reply to  No one
December 20, 2020 8:04 pm

It’s more like completely made up.

Bro. Steve
December 20, 2020 7:05 pm

Isn’t it a marvel how much these scientists can deduce from, well, pretty much nothing? Gone are the former days of man’s benighted ignorance when “science” meant that you had to go observe things. Now we can just write a computer model that tells us everything there is to know about the past and future — all from the comfort of home!

December 20, 2020 7:07 pm

I thought this might be about the World Ecnomic Forum using this modelling research for widely circulated story that unless we pay more tax – we’ll end up like Venus

December 20, 2020 7:40 pm

Venus is actually just outside the “habitable” zone. It’s only Earth and Mars that are technically inside the habitable zone where water can theoretically exist as a liquid (assuming all other things are suitable)

December 20, 2020 8:09 pm

This article stems not from scientific enquiry but comes direct from the Propaganda for Climate Change Department. It is full of assumptions, guesses, speculations, half-truths and the rest of the great propaganda panoply. It provides no facts drawn from reality, but then these are not needed in the World of Climate Change.

December 20, 2020 8:21 pm

According to recent climate modelling,

No point reading any further. GIGO !!

December 20, 2020 8:22 pm

Less than one billion years ago, the climate dramatically changed due to a runaway greenhouse effect.

Implausible on Earth because there is no “Greenhouse Effect”. It is fairytale. Earth’s average surface temperature lies close to the middle of the two thermostatically controlled ocean limits of 271.3K and 305K giving 288K average.

The wide distribution of water over the surface and the buoyancy of moist air in dry air give rise to cloudburst that generate highly reflective cloud able to reflect a large proportion of the incoming solar radiation. The shatters start going up once the sea surface temperature reaches 26C. The shutters are sufficiently closed by 30C that very little sea surface exceeds 30C.

Climate models are laughably naive in their parameterisation of clouds. If they could resolve the atmosphere to 100m altitude intervals they may have a chance of identifying the presence and level of free convection that gives rise to cloudburst. Clouds are a response to surface temperature and resultant water column. They are responsive to surface temperature rather than some vague preset parameter.

Screen Shot 2020-12-21 at 3.15.31 pm.png
December 20, 2020 8:24 pm

Let’s not forget the layer of sulphuric acid clouds..

I’m sure those must be part of their modelling 😉

December 20, 2020 8:26 pm

“We have created a suite of 3‐D climate simulations using topographic data from the Magellan mission, solar spectral irradiance estimates for 2.9 and 0.715 Gya”

There’s that word, “create”. No need to simulate reality, just assume and go dream.

Note that their version of Venus apparently was livable far earlier that Earth. Even though Venus is so close to the sun, these researchers assume that Venus cooled very quickly and had livable atmosphere.

Venus’s current atmosphere, has a surface atmosphere pressure of 82 BAR.

“despite an incident solar flux 46–70% higher than Earth receives. At its current rotation period, Venus’s climate could have remained habitable until at least 0.715 Gya

Note that whereas Earth’s early atmosphere was inhospitable to life as we currently know it.

These alleged researchers simply assume that Venus cooled much earlier that Earth did and started off with a lovely sweet breathable atmosphere at 1 BAR.
i.e. Gross assumptions made without evidence.

Given poor resolution altitude data, we used an indirect technique to try to recognize ancient river valleys. We demonstrated that younger lava flows from the surrounding volcanic plains had filled valleys in the margins of tesserae.

Here these alleged researchers used information from the Magellan project that mapped Venus by radar.

N.B. About those Magellan map images:

Over the next 14 years, among other observations it mapped approximately 90% of Venus at a resolution of about 10 kilometers.”

These alleged research characters assumed they could identify former water caused landscapes by studying lava flows with a 10km resolution…

  • Fantasy Venus.
  • Fantasy Venus atmosphere.
  • Fantasy similarities to Earth, after ignoring all of Earth’s primeval processes that turned Earth’s inhospitable atmosphere into our current pleasant nitrogen-oxygen atmosphere with trace other gasses; e.g. Argon at 0.934% by volume and CO₂ at 0.04% by volume.

At no point do these researchers show evidence that Venus started off with a pleasant 1 BAR atmosphere or even quantities of water.

William Haas
December 20, 2020 8:35 pm

What they are saying about Venus is all speculation. Their modeling is for the most part fantasy. What seems to be missing is Hydrogen. Despite having so much CO2, there in no radiant greenhouse effect in the atmosphere on Venus.

Gregg Eshelman
December 20, 2020 9:13 pm

Since Venus has a very slow retrograde rotation, my theory is that the crazy rotation, the lack of impact craters, and the excessive atmosphere all came from one incident, a massive impact that nearly obliterated the planet.

If Venus was originally the size of Mars and had a decently thick atmosphere, then along comes another planet approximately the difference between Venus’ former and current mass then smacks into it *just right* the impact energy could stop and reverse whatever Venus’ original prograde rotation was, combine most of their atmospheres, and the energy would make the combined mass squishy like a rock slushie, resulting in the current chaotic terrain.

Kind of similar to the “Great Whack” theory of the formation of Earth’s Moon, except for Venus it’d be a complete merger with little mass thrown loose so there would be the massive amount of energy required to result in the current slow retrograde rotation.

John Tillman
Reply to  Gregg Eshelman
December 21, 2020 4:09 am

Mercury also rotated slowly, albeit still in the standard direction. IMO this suggests that gravitational forces play a role.

Reply to  Gregg Eshelman
December 21, 2020 3:34 pm

the lack of impact craters”

Uh, no!
Venus has lots of impact craters. And those craters were identified through radar that has a 10km resolution.


Numerous impact craters >15 km in diameter on Venus have been named for famous women (last names). Some smaller impact craters <15 km in diameter have been given common female first names from various ethnic groups.”

“The Crater Database

The database tables include the name (where applied), coordinates, diameter, modification state, crater morphologic type, and mean elevation of 967 craters interpreted to be of impact origin within the area of the planet imaged by the Magellan spacecraft between 1990 and 1994.”

Three large impact craters with diameters ranging from 37 km (23 mi) to 65 km (40 mi) are visible in the fractured plains.

Venus has active volcanism, weather and erosion.

Reply to  Gregg Eshelman
December 21, 2020 6:24 pm

I’ve been trying to think how a collision like that could work. The only thing I’ve been able to come up with is this:

First off, if the collider impacts the planet head on, there will be no moon created and the rotational speed of the planet will only be changed to the extent that some of the rotational energy from the planet will have to be transferred to the mass of the collider, in order to get ithis mass spinning in the same direction as the original planet. If the collider is the same mass as the planet, then the speed of rotation will be halved. One problem with this scenario is that all of the forward momentum of the collider will be transferred to the planet. If the collider as big as the original planet, than the orbital velocity of the orginal planet will either be sped up or slowed down by a significant amount, and there is no evidence that the orbit of Venus has been perturbed by that much in the past. Another problem is that a direct hit can only slow the rotational rate of the plane, ut can’t reverse it.
So we are left with a glancing blow. To slow the rotational rate, the collider will have to hit the planet on the side that is rotating towards the collider. A glancing blow will use some of it’s forward momentum to reduce the rotational energy of the planet, and some of it to change the orbital speed of the planet. A glancing blow will also throw a lot of debris into orbit around the planet which will eventually form a moon. A collision of this type described above will create a moon that is in a retrograde orbit, travelling in the opposite direction that the planet is spinning.
Over time, rotational energy from the planet will be transferred to that moon, however since the moon is in a retrograde orbit, this energy will result in the moon’s orbital speed being reduced and eventually the moon will crash into the planet transferring the rest of the moon’s orbital momentum to the planets rotational rate.

Rory Forbes
December 20, 2020 9:22 pm

Based on my limited understanding of the tectonic dynamics of Venus, it’s fairly certain that it has been almost perpetually actively tectonic since it formed, unlike earth that formed a semi-stable crust. During the 1 billion years discussed in that modeled “study”, it’s unlikely there was ever any long lasting stable crust … at least not for long enough to allow for standing water. Even on Earth’s far more stable surface over the past 1 billion years the continents are very unlike their earlier land masses and the climates have also changed as well.

In other words, their modeled, 100% speculative venture in fantasy has N0 chance, 99 times out of 100, of providing ANY useful information. It is not only pointless driven, it hasn’t any scientific merit at all.

Jeff Alberts
Reply to  Rory Forbes
December 21, 2020 9:33 am

unlike earth that formed a semi-stable crust.”

How do we “know” that?

Rory Forbes
Reply to  Jeff Alberts
December 21, 2020 12:30 pm

We know that from empirical evidence. You’re standing on a “semi-stable crust”. Oddly enough, this planet wasn’t always like it is at present. It has passed through considerable evolution.

Hoyt Clagwell
December 20, 2020 10:18 pm

Why no mention of the fact that climate change is what made the Earth so livable? It was largely covered in snow and ice not too long ago, but climate change saved us and millions of other life forms. There’s nothing inherently “bad” about climate change.

Ken Irwin
Reply to  Hoyt Clagwell
December 21, 2020 12:20 am

Absolutely ! Thanks to climate change, the once Venus like Earth has become habitable.

And the eco-loons think that’s ba !

Climate believer
Reply to  Hoyt Clagwell
December 21, 2020 4:54 am

Hoyt Clagwell report to room 101 immediately…..

Alexy Scherbakoff
December 20, 2020 10:50 pm

I give this story an imdb score of 2.1

December 20, 2020 11:21 pm

The radiative greenhouse effect cannot explain why the temperature within the atmosphere of Venus is much the same as that on Earth at the same pressure after adjusting only for distance from the sun.
Only my convective overturning concept provides an explanation.
If there is no convective overturning then conduction results in an isothermal atmosphere.
Only convection produces the transformation to and fro between kinetic and potential energy so it is that process which delays radiative losses back to space and thereby heats the surface.
See my articles on this site and elsewhere created with the kind assistance of Philip Mulholland.

John Tillman
Reply to  Stephen Wilde
December 21, 2020 4:11 am

Right under Venus’ cloud decks, air temperature is very cold.

Peta of Newark
December 21, 2020 12:30 am

“”lack of impact craters on Venus.””

With an atmosphere as dense as Venus’, would *anything* falling even make it to the surface?

“”an intensive period of volcanism pumped enough carbon dioxide””

Am I crazy, maybe, but doesn’t the CO2 coming from earth’s volcanoes originate from ancient and tectonically subducted limestone. As per what happens in a Lime (Cement) Kiln
Limestone created by ‘Life Processes” – does it come from *anywhere* else?

“”resurfaced by volcanic activity hundreds of millions of years ago”
Considering that the tectonics and volcanoes are powered by heat from decaying radio-isotopes…
… that *they* were all created in one or more super-nova *at *least* 5 billion yrs ago
…AND that they all have ‘Half-Lives’
– what caused them to wait until a few hundred million years ago before bursting into life?

[Possibly a near miss from an errant planet-sized lump wandering the Galaxy?
Or the what-dya-call-them hi-way builders from Hitchhikers – MUCH more likely than the garbage we’re presented here]

I’d assert and have done, that volcanoes are Fountains of Ambrosia. For plants.
That the lack of tectonics on Mars explains its ‘Climate’ and that seemingly there *was* liquid water and life there – how could there not?

Also assert that the relentless expansion of deserts on Earth, accelerated by our farming, city-building and (de)forestry practices will turn Earth into another Mars
The radio isotypes that power ‘resurfacing’ are now all very old.
Modern volcanoes are few & far between *and* are feeble weak affairs compared to how they were and what created the blossoming of life.

Re the errant planet. Does that connect with the age of our oil/coal reserves, created by a massive greening of Earth circa 100mya- stuff grew so fast it couldn’t decompose fast enough and got buried?
Maybe there is a diamond in this mountain of rocks?

Otherwise *far* too many Weasel Words – can someone count them please?

December 21, 2020 12:53 am

It is currently raining in london england, A clear sign of climate change.. We don’t need venus or mars as a lesson in green houses gasses, everything is climate change, a sunny day, snow, birds singing, wind, no wind…

To bed B
December 21, 2020 12:56 am

“The Venusian surface has been altered by objects from outside the planet as well as by forces from within. Impact craters dot the landscape, created by meteorites that passed through the atmosphere and struck the surface. Nearly all solid bodies in the solar system bear the scars of meteoritic impacts, with small craters typically being more common than large ones. This general tendency is encountered on Venus as well—craters a few hundred kilometres across are present but rare, while craters tens of kilometres in diameter and smaller are common. Venus has an interesting limitation, however, in that craters smaller than about 1.5–2 km (1–1.2 miles) in diameter are not found. Their absence is attributable to the planet’s dense atmosphere, which causes intense frictional heating and strong aerodynamic forces as meteorites plunge through it at high velocities. The larger meteorites reach the surface intact, but the smaller ones are slowed and fragmented in the atmosphere. In fact, craters several kilometres in size—i.e., near the minimum size observed—tend not to be circular. Instead they have complex shapes, often with several irregular pits rather than a single central depression, which suggests that the impacting body broke up into a number of fragments that struck the surface individually. Radar images also show diffuse dark and bright “smudges” that may be have resulted from the explosions of small meteorites above the surface.”
Encyclopedia Britannica

Wind speeds on the surface are only 10 km/h but very dense. The pressure is the same as under 900 m of water. Why the need for a resurfacing event and not just erosion?

Matthew Sykes
December 21, 2020 2:01 am

And the air temp at the bottom of the grand canyon is a few degrees warmer. Boyles law. Compress gas and it warms.

Reply to  Matthew Sykes
December 21, 2020 11:54 am

The act of compressing a gas warms it. However gas at a constant pressure is neither warmed nor cooled by the pressure.
Think of it another way.
When you pump up a bicycles tire, the tire heats up. However once you stop pumping air, the tire quickly returns to the ambient temperature.

December 21, 2020 3:38 am

Junk science redefined.

Mark Whitney
December 21, 2020 4:24 am
John Tillman
Reply to  Mark Whitney
December 22, 2020 2:49 pm

It’s not their distances from the Sun but their rotation rates which explain the different fates of twin planets Venus and Earth.

While Venus gets twice as much radiation at the top of its atmosphere, its surface recieves only 20% as much sunlight (direct and indirect) as our wonderful world.

December 21, 2020 4:25 am

and a deja vu of Holdrens bullsh*t theory on venus

very old white guy
December 21, 2020 5:01 am

everyday another thing that makes you shake your head and laugh.

very old white guy
December 21, 2020 5:03 am

I am sure it has nothing to do with it’s proximity to the sun. scheesh.

Nick Schroeder
December 21, 2020 5:05 am

Venus, we are told, has an atmosphere that is almost pure carbon dioxide and an extremely high surface temperature, 750 K, and this is allegedly due to the radiative greenhouse effect, RGHE. But the only apparent defense is, “Well, WHAT else could it BE?!” (besides/also molten core volcanism)

Well, what follows is the else it could be: (Q = U * A * ΔT) aka a contiguous participating media.

Venus is 70% of the Earth’s distance to the sun, its average solar constant/irradiance is about twice as intense as that of earth, 2,602 W/m^2 as opposed to 1,361 W/m^2.

But the albedo of Venus is 0.77 compared to 0.31 for the Earth – or – Venus 601.5 W/m^2 net ASR (absorbed solar radiation) compared to Earth 943.9 W/m^2 net ASR.

The Venusian atmosphere is 250 km thick as opposed to Earth’s at 100 km. Picture how hot you would get stacking 1.5 more blankets on your bed. RGHE’s got jack to do with it, it’s all Q = U * A * ΔT.

The thermal conductivity of carbon dioxide is about half that of air, 0.0146 W/m-K as opposed to 0.0240 W/m-K so it takes twice the ΔT/m to move the same kJ from surface to ToA.

Put the higher irradiance & albedo (lower Q = lower ΔT), thickness (greater thickness increases ΔT) and conductivity (lower conductivity raises ΔT) all together: 601.5/943.9 * 250/100 * 0.0240/0.0146 = 2.61.

So, Q = U * A * ΔT suggests that the Venusian ΔT would be 2.61 times greater than that of Earth. If the surface of the Earth is 15C/288K and ToA is effectively 0K then Earth ΔT = 288K. Venus ΔT would be 2.61 * 288 K = 748.8 K surface temperature.

All explained, no need for any S-B BB LWIR RGHE hocus pocus.

Simplest explanation for the observation.

(NASA planetary data sheet, engr tool box, first principles & math)

Bill Marsh
December 21, 2020 5:10 am

Seems to me that this ‘study’ was designed to provide the answers the authors were looking for. Is there any evidence that Venus ever had as much surface water as earth at any time in it’s history? If it’s atmosphere was ‘earth-like’ wouldn’t it’s proximity to solar radiation and slow rotational speed have made it unlikely that the planet cold retain surface water of any amount? Is there any evidence that Venus’ rotational speed was ever ‘earth-like’? I think the mars sized object collision with a young earth (which created the Moon) had something to do with earth’s rotational speed?

Reply to  Bill Marsh
December 21, 2020 11:56 am

We’ve had satellites that can map the surface of Venus using radar. To date no evidence of ancient surface water has been found.

Tom in Florida
December 21, 2020 5:42 am

“It likely also had oceans, rain, perhaps snow, maybe continents and plate tectonics, and even more speculatively, perhaps even surface life. ”

Without a magnetosphere?

But at least they openly admit it is all speculative with the possibility of life “even more speculative”.

Fight Climate Fear. Warmer is Better.

December 21, 2020 5:54 am

Those silly Venusians. See what happens when you don’t pay a carbon tax? 😉

December 21, 2020 6:24 am

Study: “Earth was once more Venus-like, but climate change made it inhabitable”

In science it is often a useful exercise to turn a statement around and see if it still makes sense. The object of this exercise is to test your assumptions. If I take a telescope and look through it the wrong way what happens? I discover that I have also made a microscope.

Richard Feynman’s superb statement that we discover the laws of science by guessing carries a deeper truth, namely that we also make observations by guessing. Our guesses are comparators of what we are seeing. The first description of a biological cell when made through a microscope used the concept of a monk’s cell; this familiar name of an enclosed space was used by the observer to describe the objects being seen. Had the analogy of a bubble come to his mind we may just as easily be talking knowledgeably about the biology of bubbles.

So, what do we know about Venus and what can we deduce from our knowledge?
From astronomy we know that:
1.   Venus is closer to the Sun than the Earth.
2.   Venus is about the same size and mass as the Earth.
3.   Venus has no moon.
4.   Venus is a bright planet.
5.   From observations of the transit of Venus Mikhail Lomonosov discovered that the planet has an atmosphere.
6.   From radar studies we know that Venus has a retrograde rotation.

From direct exploration using planetary probes we know that:
7.   Venus has a thick atmosphere of carbon dioxide gas and it has a searing surface temperature.
8.   Venus has a young aged surface with few impact craters.
9.   Venus has a surface topography with two highland areas Ishtar Terra and Aphrodite Terra indicative of long-term crustal formation processes.

I will start with the interesting fact that Venus has a significant quantity of Nitrogen gas in its atmosphere (3.5% by volume) and with a surface pressure of 92 bars, this means that by Dalton’s law of partial pressures the planet has an atmospheric component of 3.22 bars of nitrogen gas. By comparison the earth has a partial surface pressure of 0.79 bars of nitrogen and so Venus has 4 times as much nitrogen by mass in its atmosphere as the earth does. This is important for a number of reasons.

First this suggests that Venus has always had a significant atmospheric pressure on its surface from its time of formation. Certainly, there would have been sufficient pressure for liquid water to exist even under the reduced insolation of the early faint Sun. This is because of its closer proximity to the Sun the planet Venus would be in the reduced radius “Goldilocks zone” at its time of planetary formation.

But where does the nitrogen gas for the supposed thick atmosphere of early Venus come from?
I believe that the suggestion by Ian Miller in his 2001 paper “Early Martian Atmosphere and Biogenesis” has application here. Metal nitrides formed in the high temperatures of the early solar system nebula provide a valid mechanism to allow nitrogen to be accumulated in solid mineral form during the accretion of the planet Venus.

So, if we have on the surface of the early Venus a nitrogen atmosphere with liquid surface water, why is Venus now a carbon dioxide world?
If we assume that the standard processes of vulcanism on a terrestrial planet such as Venus produce a continual outgassing of carbon dioxide gas into the atmosphere, and that the early ocean of Venus was acidic (all that volcanic sulphur) and further that the ocean was warm, then the only place for the carbon dioxide to accumulate would be in the atmosphere.

So, as time moved on and the Sun became brighter, if it had a low albedo earth-like, water vapour dominated atmosphere then Venus would become hotter. Eventually the increasing solar irradiance from the developing Sun would trigger planetary surface water boiling and the oceans of Venus would evaporate into space.

I discussed the timing of this idea for the transformation of Venus in section 4.4 of our paper <a href=””>Inverse Climate Modelling Study of the Planet Venus

Reply to  Philip Mulholland
December 21, 2020 6:31 am

Ho hum, I see there are new rules for posting links here.
Inverse Climate Modelling Study of the Planet Venus

Reply to  Philip Mulholland
December 22, 2020 3:32 am

You forgot to mention that the Solar Irradiance on Venus is almost exactly twice that of Earth.
We get 1300 W/m^2. Venus gets 2600 W/m^2.

Reply to  JCalvertN(UK)
December 22, 2020 8:48 am

“You forgot to mention that the Solar Irradiance on Venus is almost exactly twice that of Earth”
That is one of those “Yes, but” issues. I said Venus is closer to the Sun so the irradiance must be higher and that is why I said ancient Venus was inside the Goldilocks zone of a weaker early Sun.
But, the albedo of the modern sulphuric acid clouded Venus (0.77) is much higher than the water dominated albedo of the Earth (0.306)
Earth captures 1361*(1-0.306) = 944 W/m^2
Venus captures 2601*(1-0.77) = 598.3 W/m^2
So Earth is clearly going to be warmer than Venus (Yeah right, … it’s complicated).

Reply to  Philip Mulholland
December 22, 2020 10:25 pm

I must admit I should have read your post more carefully. (But I don’t buy the albedo argument. Albedo effect doesn’t happen at top of atmosphere)

Reply to  JCalvertN(UK)
December 23, 2020 2:56 am

“Albedo effect doesn’t happen at top of atmosphere”
It absolutely and emphatically does happen at the top of the Venusian atmosphere, that is where the reflective clouds are!. That is also why Venus is the brightest planet we see from the Earth.
The sunlight here on Earth does not get dimmer on a cloudy day?
Where does the reflected (and therefore not absorbed) light go to?

December 21, 2020 6:42 am

”… more Earth-like …” ?

The Earth is more Heaven-like than Hell

David S
December 21, 2020 7:12 am

“It can be speculated that an intensive period of volcanism pumped enough carbon dioxide into the atmosphere to cause this great climate change event that evaporated the oceans and caused the end of the water cycle.”

t can also be speculated that the authors are using the WAG method.. Wild A** Guess,

The authors haven’t yet claimed that this is earth’s future unless we change our wicked ways. But give them a while and they will make that claim.

December 21, 2020 7:33 am

There is little or no water vapor in the Venus atmosphere, so where did that ocean go? The clouds are sulfuric acid aerosol created from sulfur dioxide and water that is measured in ppm.

December 21, 2020 8:47 am

“Venus was once more Earth-like, but climate change made it uninhabitable”
So, someone either thinks that Venus WAS habitable, or they are too ignorant to understand their own heading, or they are intentionally trying to exaggerate (lie) and mislead.

The heading is a lie … the only to reason to continue with the article is to find more lies.

December 21, 2020 8:49 am

All previous models found that Venus never cooled down enough for oceans to form.
Please explain why all previous models were wrong and yours is correct.

John Endicott
Reply to  MarkW
December 21, 2020 9:56 am

First they need to prove *any* of the models are capable of being correct. Doesn’t matter what the models say when you have no reason to believe the models are accurately modeling what they claim to be modeling.

December 21, 2020 8:58 am

Likely, Venus initially had comparable amounts of H2O, N2, and CO2 as does Earth.
But Venus lacks a magnetic field. Earth’s magnetic field protects its upper atmosphere from charged solar particles and disassociation of the H2O molecule. Atmospheric water on Venus, not so protected, slowly disassociated, and the H2 formed, having a greater molecular velocity than the Venusian escape velocity, was gradually lost over time. Evidence that such mass fractionation occurred is observed today in the much greater D/H isotopic ratio of hydrogen on Venus.

On Earth, atmospheric water vapor produces most of the greenhouse warming effect, sometimes estimated at some 30 degree-C. Loss of Earth’s atmospheric water vapor (assuming all other parameters constant, including cloud albedo) would cause Earth to cool. Presumably, loss of water vapor from Venus also had a cooling effect.

Venus’ inventory of CO2 is concentrated in its atmosphere, in large part because its high surface temperature disassociates the common condensed species, carbonate. On Earth, much of the near-surface carbon exists in carbonate. The massive atmospheric CO2 contributes to Venus’ elevated temperature, and this effect greatly outweighs greenhouse cooling from loss of water vapor.

John Endicott
December 21, 2020 9:57 am

<I>According to recent climate modelling, </I>

No need to read past that sentence because you know anything that follows is pure speculation based on no real data.

December 21, 2020 10:00 am

Mars has an atmosphere comprised of 95% CO2, but temperatures range from -150°C to 20°C.

Surely if CO2 was the temperature control knob it to would have the same surface temperature as Venus.

Tom in Florida
Reply to  Rusty
December 21, 2020 2:19 pm

The atmosphere of Mars is very thin so 95% of squat is still squat. The two are not comparable.

Fight Climate Fear. Warmer is Better.

December 21, 2020 10:06 am

They may not be trying to SAY it, but with the headline (which is all that most read) they’re certainly trying to frighten people into believing it.

Robert of Texas
December 21, 2020 4:03 pm

“we assume”

That pretty much wraps up their entire story.

December 22, 2020 3:21 am

“…an interesting intellectual exercise…”, also known as “mental masturbation”. Sorry to offend, but there’s no other way to adequately describe this work of fiction pretending to be science.

Another point – claiming that the lack of surface features at the bottom of such a heavy atmosphere must mean volcanic action resurfaces the planet regularly is just complete ignorance. One big likelihood is that no meteorites (etc) can get through the atmosphere in order to impact the surface.

A final question – how do the “know” that Venus changed 1 billion years ago? What evidence do they have that it was ever any different than today?

John Tillman
Reply to  Hivemind
December 22, 2020 12:49 pm

To fit their narrative, the GIGO modelers assume that the reworking of Venus’ surface occurred in a short period about a billion years ago. The evidence suggests however that resurfacing is a continuous process, the Venusian equivalent of tectonics.

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