From the AGU weekly highlights:
Evaluating solutions to the faint young Sun problem
During the Archean eon, between about 3.8 billion years ago and 2.5 billion years ago, the Sun was about 20 to 25 percent fainter than it is today. With less sunlight to warm the Earth, the oceans should have been frozen over, but geological evidence suggests that this was not the case.
Some proposed solutions to this problem, known as the faint young Sun problem, include an atmospheric composition with higher concentrations of greenhouse gases, higher atmospheric pressure, increased cloud droplet size, and changes in land distribution and Earth’s rotation rate.
Charnay et al. used a three-dimensional global climate model coupled to a dynamic ocean model to examine these possible solutions.
They find that an atmosphere that had 100 millibars of carbon dioxide and 2 millibars of methane 3.8 billion years ago, and 10 millibars of carbon dioxide and 2 millibars of methane 2.5 billion years ago—levels corresponding to 25 to 250 times the present level of carbon dioxide and 1000 times the present level of methane—would have made it possible for Earth to have had a temperate climate with a mean surface temperature between 10 and 20 degrees Celsius (50 and 68 degrees Fahrenheit), close to the current climate.
The authors suggest that these levels of greenhouse gases are consistent with geological data, making such an atmospheric composition a viable solution to the faint young Sun problem. Cloud feedbacks were also shown to prevent a full snowball Earth from developing during that time period. The authors find that some of the other potential solutions could have produced some warming during the Archean, but none individually produced enough warming to avoid widespread glaciation.
Source: Journal of Geophysical Research-Atmospheres, doi:10.1002/jgrd.50808, 2013 http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50808/abstract
Exploring the faint young Sun problem and the possible climates of the Archean Earth with a 3-D GCM
[1] Different solutions have been proposed to solve the “faint young Sun problem,” defined by the fact that the Earth was not fully frozen during the Archean despite the fainter Sun. Most previous studies were performed with simple 1-D radiative convective models and did not account well for the clouds and ice-albedo feedback or the atmospheric and oceanic transport of energy. We apply a global climate model (GCM) to test the different solutions to the faint young Sun problem. We explore the effect of greenhouse gases (CO2 and CH4), atmospheric pressure, cloud droplet size, land distribution, and Earth’s rotation rate. We show that neglecting organic haze, 100 mbar of CO2 with 2 mbar of CH4 at 3.8 Ga and 10 mbar of CO2 with 2 mbar of CH4 at 2.5 Ga allow a temperate climate (mean surface temperature between 10°C and 20°C). Such amounts of greenhouse gases remain consistent with the geological data. Removing continents produces a warming lower than +4°C. The effect of rotation rate is even more limited. Larger droplets (radii of 17 μm versus 12 μm) and a doubling of the atmospheric pressure produce a similar warming of around +7°C. In our model, ice-free water belts can be maintained up to 25°N/S with less than 1 mbar of CO2 and no methane. An interesting cloud feedback appears above cold oceans, stopping the glaciation. Such a resistance against full glaciation tends to strongly mitigate the faint young Sun problem.
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Given that the moon was supposedly created by a massive planetary collision I’d be very surprised if this had not force an orbital change upon the earth.
Further, as is mentioned above in comments, a partially formed, mobile crust would have released large amounts of internal heat.
Working on this problem with a climate model would appear to be terribly limiting.
If the sun was “25% fainter”, then presumably the ancient earth would have received about 1020 watts per square metre, rather than the current 1360. Thus the equilibrium black body temperature at the subsolar point (ignoring atmospheric transmission effects) would have been around 93°C, rather than 120° as at present. Either of these rates of energy input is easily sufficient to ensure that the earth’s water thermostat (© Willis) controls the overall temperature in the long term. What’s the problem, or have I missed something centrally important here?
they used a climate model ?why ? would have been a lot quicker and less expensive to use a pack of tarot cards.the results would be at least as robust as those from the climate model.
What happened to the turtles? I liked them better than the models, all the way down.
At the time the oceans were acidic, anaerobic and contained huge levels of dissolved transition metal salts. Many of these, like iron, nickel, cobalt, copper and manganese are colored and the oceans would have been dark brown and not blue. The difference in albedo would be substantial and the very top few centimeters of the oceans would absorb most of the incoming solar energy..
The land would have consisted of dark sulphides and not the lighter oxides.
The land and ocean albedos would have been quite different from now.
Nir Shaviv has a partial explanation based upon cosmic rays. He wrote:
The sun, like other stars of its type, is slowly increasing its energy output as it converts its Hydrogen into Helium. 4.5 Billion years ago, the sun was 30% fainter than it is today and Earth should have been frozen solid, but it wasn’t. This problem was coined as the “Faint Sun Paradox” by Carl Sagan.
If the Cosmic Ray Flux climate link is real, it significantly extenuates this discrepancy. This is because the young sun, which was rotating much faster, necessarily had a much stronger solar wind. This implies that less cosmic rays from the galaxy could have reached Earth because cosmic rays lose energy in the solar wind as they propagate from the interstellar medium to Earth. Since less cosmic rays implies a higher temperature, this effect will tend to compensate for the fainter sun.
Plugging in the numbers reveals that about 2/3’s of the temperature increase required to warm the young Earth to above today’s temperature, can be explained with this effect. The remaining 1/3 or so, can be explained with moderate amounts of greenhouse gases, such as 0.01 bar of CO2 (amounts which are consistent with geological constraints), or some NH3 or CH4.
See: http://www.sciencebits.com/ice-ages
Too many differences from the present for this thread to have any point other a bit of fun.
Sorry, we cannot mimic the climate of the last 10 years with GCM’s. How could we possibly use them to mimic a different planet , which Earth was, 3 billion years ago?
Can I get a refund!
mkelly says:
September 24, 2013 at 1:44 pm
No, methane alone wouldn’t confirm the existence of life on Mars, but it would tend to support the hypothesis.
Duster says:
September 24, 2013 at 2:05 pm
There is evidence of seasons in both the Paleozoic & Mesozoic Eras. Dinosaurs, crocodilians & even amphibians near the Poles is evidence of a warmer, more equable climate, not a falsification of seasonality. By equable in this case is meant a less steep gradient in temperature from the Equator to the Poles.
BTW, GCMs cannot reproduce Cretaceous climate without assuming preposterously high ECS, even with the much higher CO2 levels of the Period. A proposed fix is less cloudiness due to less biological productivity in the then very warm tropical oceans, which of course the models can’t handle.
PS: Which is not to say that it didn’t get cold at the Poles in the Mesozoic. It did, naturally, with dark winters then as now. But dinosaurs & crocodilians (archosaurs) have four-chambered hearts (down-rated with a hole for modern, aquatic crocs), while the amphibians hibernated.
The “faint sun paradox” is a farce.
Three point eight to 2.5 billion years ago planet Earth was releasing far greater amounts of the heat of formation than it does today.
In addition to this, the amounts of radioactively-generated heat in the core were also much greater.
This is the reason why the ocean was warm and liquid; the ocean was being heated from the top down by a fainter sun than we have today, and it was also being heated from the bottom up by a much hotter planet.
The situation didn’t have anything to do with an imaginary “greenhouse effect” that definitely does not exist or any of the other suggestions.
As an aside, the thermal structure of the ocean was also much different back then, being coolest in the mid-depths and warmer both above and below.
Planet Earth was a much different place back then.
jjfox says:
September 24, 2013 at 4:30 pm
Then there’s this:
http://wattsupwiththat.com/2010/04/07/faint-sun-paradox-explained-by-stanford-greenhouse-effect-not-involved/
@GlynnMhor says:
>What assumptions were used for the cloud feedbacks, given that there is doubt as to the magnitude and even the sign of cloud effects?
Well, I had a similar question right off the bat: What forcing value was used to calculate how much CO2 was needed to get that equilibrium temperature? Was it 0.8? 1.0? 3.2?
“””Evaluating solutions to the faint young Sun problem
During the Archean eon, between about 3.8 billion years ago and 2.5 billion years ago, the Sun was about 20 to 25 percent fainter than it is today. With less sunlight to warm the Earth, the oceans should have been frozen over, but geological evidence suggests that this was not the case.”””
FWIW
Where was the faint sun located?
Near its own star forming region or near another?
The higher energetic level of GCR and Dust.
Like GCR at the Peta and Giga and Mega electron volt range of energy might also ionize some Earthly atmospheric gaseous.
Not to mention what it would do to the inner solar system.
It would appear from the collective wisdom of the WUWT commenters here that it does not need a Green House Gas explanation from another highly suspect climate model to solve the Faint Sun Paradox and the failure of the global oceans to freeze over due to Solar radiation levels being some 20% to 25% lower during the later Archean period.
There is a whole gamut of explanations for solving the Faint Sun Paradox, none of which are likely to be the sole explanation but most or all of which operated collectively to negate and counter the lack of or lower solar radiation of the late Archean period and which led to an Earth temperature that maintained water as a fluid and therefore created the conditions for life to evolve and exist..
I just collected a few of the comments from the above WUWT posts that provide the various and alternative reasons as explanations for solving the FSP.. Other commenters have made very similar points to those quoted.
Carrick 12.26 pm
Sun’s interior rotation rates more rapid leading to a flatter lumnosity curve during this era.
Thomasinga 11.30 am and a number of other commenters
Gravitational force heating due to ;
Earth’s orbit more elliptical and elongated.
Earth’s orbit much closer to the Sun
Moon’s orbit close into Earth and far more elliptical and elongated
Planetary orbits more elongated and probably swinging in much closer to Earth at various points in their various orbits around the Sun
Therefore planetary orbits being far more elliptical and elongated led to high variations in gravitational tidal forces acting on the Earth leading to heating of the Earth’s interior..
Jupiter’s “Io” moon with it’s numerous volcanoes is the classic present example of gravitational tidal forces from both Jupiter’s mass and the mases of Jupiter’s other moons all creating strong gravitationally induced tidal forces on Io leading to interior heating of that planet and the presence of a number of volcanoes on Io.
Earth’s mantle was far thinner and far more plastic allowing much greater tectonic movement due to gravitationally induced tidal forces from other planets, the Moon and the Sun and planets.
bubbagyro 11.46am
Radioactive isotope decay.
Radioactive isotopes 3.8 billion years ago were obviously in much higher concentrations than today.
The 2 billion year old OKLA fossil fission reactors in Gabon are the only surviving remnants of what could have been a number of these natural nuclear fission reactors existent in early Earth that ran on the concentrations of radio active isotopes for some hundreds of millions or a couple of billion years during Earth’s early eras whenever local climatic conditions [ rainfall ] were suitable.
http://oklo.curtin.edu.au/
And it is of interest to quote Wiki here;
The Archean is one of the four principal eons of Earth history. When the Archean began, the Earth’s heat flow was nearly three times as high as it is today, and it was still twice the current level at the transition from the Archean to the Proterozoic (2,500 Ma). The extra heat was the result of a mix of remnant heat from planetary accretion, heat from the formation of the Earth’s core, and heat produced by radioactive elements.
Barry Cullen; 12.09 pm
Atmospheric density much higher and therefore a different adiabatic lapse rate and consequent lower storm heights leading to considerably less energy being radiated back into space than presently theerby countering the reduced radiation emissions from the Sun.
Raindrop studies support the Archean higher density atmosphere hypothesis.
It seems that one does not have to rely on some unproven climate modeled green house effect to account for and solve the Faint Sun Paradox..
All the above explanations of course are unproven and just hypothesis as is the climate modeled green house effect.
But all the above hypothesis are an equal and I suspect, a much more acceptable explanation for explaining and solving the Faint Sun Paradox than any climate modeled green house effect which at best might have been a minor contributor compared to gravitation tidal forces and the isotope decay contribution to the warming of the Earth during the long Archean era.
I vote for the gravitational force heating due to a nearer moon and more elliptical orbit of Earth and moon around the sun. We can affirm today that this is a significant factor just by observing Saturn’s inner moon temps. These moons are a long, long way from Old Sol, which is small indeed in their sky.
Now wait a minute. Do we know how much “organic haze” there was? Was this volcanic ash? Dust? Smoke from fires? This kind of atmospheric stuff cannot be ignored, especially if it is nonstop. If the Sun were fainter, any amount of haze would prevent much needed warmth from getting into the oceans around the equatorial belt.
So it appears to me they ignored a most important factor. Why?
The faint young sun appears to be a real problem.
But life did evolve 4.0 to 3.6 billion years ago and there really was a great oxidization event starting at 2.6 billion years ago lasting to 1.0 billion years ago and there really was at least 4 large snowball Earth episodes starting at 2.4 billion years ago and complex lifeforms really did start appearing about 620 million years ago.
And we are most certainly here 4.45 billion years after the Earth formed so the faint young sun is not so much a paradox, but something that was overcome (either easily or just barely but it was nevertheless).
If we could trust the climate models to accurately represent the climate then we would have to rely on the scenarios they present. But we can’t. We must rely on what really happened and what really is happening today.
@shenanigans24
Rain-dance denier.
But there is no real problem about why the Earth was warm during the Achaean era. We know that both the Achaeans and the Trojans burnt their dead during the ten-year long war, so we know that huge amounts of CO2 would have been produced to keep the Earth warm.
and if the models could not explain the paradox folks would of course reject them.
Absent a different explanation ( in numbers not in words ) one is left with the conclusion that the paradox is solvable under certain assumptions. The presence of a good explanation does not rule out the possibility of a better explanation. The course of science is for other people to know offer better solutions.
I feel their statement “Larger droplets (radii of 17 μm versus 12 μm) and a doubling of the atmospheric pressure produce a similar warming of around +7°C.” is way, way off in the case of pressure, about one magnitude to low. Both Earth’s atmosphere and Venus’s are only 6.7 times of doubling in pressure terms (mass) and both are totally opaque (so very near to totally) to both water vapors and carbondioxide’s lines from the surface upward and bands. I need to revisit the Beer-Lambert law and optical depth in releation to what they are claiming of both incoming solar radiation absorbed by the atmosphere itself or reflected and the outgoing infrared from the surface. Wish I could see their calculation or logic explaining how they came up with this +7°C figure for a pressure doubling.
Mosher writes “The course of science is for other people to know offer better solutions.”
There is so very much about the distant past that we dont and cant ever know. This study is based on assumption after assumption. At some point one leaves the realm of science and it becomes something else.
“””””……MattS says:
September 24, 2013 at 11:53 am
Latitude,
“I thought it was logarithmic”
Yes it is, but the authors are talking about a 1 to 2 order of magnitude increase from current CO2 levels. That is going to make a noticeable difference even if the effect is logarithmic……..””””””
I wish people would stop saying “it” is logarithmic.
The problem with that is it doesn’t make any difference whether you take the logarithm of the CO2 data or whether you take the logarithm of the Temperature data; or for that matter if you do both; or if you do neither. The resulting plots are equally uncertain.
Please look up the power series for Ln(1+x). or e^x for small x .
And don’t give me any Beer’s Law claim of a theoretical foundation. Beer’s law is a law for ABSORPTION of radiant energy, as a function of absorbing species concentration.
It is NOT a law for TRANSMISSION of radiant energy as a function of absorbing species concentration.
Beer’s law ASSUMES that absorbed radiant energy stays dead.
Absorbed radiant energy NEVER STAYS DEAD; it is re-emitted at some other (longer) wavelength, and gets transmitted anyway.
“Beer’s law is a law for ABSORPTION of radiant energy, as a function of absorbing species concentration.”
and
“And don’t give me any Beer’s Law claim of a theoretical foundation. Beer’s law is a law for ABSORPTION of radiant energy, as a function of absorbing species concentration.”
Whew… if you are saying that the absorbance becomes linear with the concentration, true, opaque is total absorption. But the transimttance is dependent on the concentration times length of path through the media (exponentially), the optical mass that hinders passage that can be via scattering, refection or absorption, the tau.s in I = I0 * exp(-m(τa + τb + τc + … )). Am I not right? Seems something hit a raw nerve with you George since I think I was the only commenter above that even mentioning it, be assured if I do use that law, and I will, I will be careful to do so properly. If you are saying it can be misused or misinterpreted easily, I agree. But come on, the ratio of the intensities are the transmissivity and it is embedded in the definition of the law. Or have I misstated something, used a wrong word above. I usually speak here loosely and don’t take the time to check that every single term is perfect. Or, am I missing something you are trying to say?