From the University of Colorado at Boulder a claim that computer modeling has solved the problem, with an atmosphere that is 20,000 parts per million of CO2 and 1,000 ppm of methane.
CU study shows how early Earth kept warm enough to support life
Scientists tackle faint young sun paradox with 3-D climate models
Solving the “faint young sun paradox” — explaining how early Earth was warm and habitable for life beginning more than 3 billion years ago even though the sun was 20 percent dimmer than today — may not be as difficult as believed, says a new University of Colorado Boulder study.
In fact, two CU-Boulder researchers say all that may have been required to sustain liquid water and primitive life on Earth during the Archean eon 2.8 billion years ago were reasonable atmospheric carbon dioxide amounts believed to be present at the time and perhaps a dash of methane. The key to the solution was the use of sophisticated three-dimensional climate models that were run for thousands of hours on CU’s Janus supercomputer, rather than crude, one-dimensional models used by almost all scientists attempting to solve the paradox, said doctoral student Eric Wolf, lead study author.
“It’s really not that hard in a three-dimensional climate model to get average surface temperatures during the Archean that are in fact moderate,” said Wolf, a doctoral student in CU-Boulder’s atmospheric and oceanic sciences department. “Our models indicate the Archean climate may have been similar to our present climate, perhaps a little cooler. Even if Earth was sliding in and out of glacial periods back then, there still would have been a large amount of liquid water in equatorial regions, just like today.”
Evolutionary biologists believe life arose on Earth as simple cells roughly 3.5 billion years ago, about a billion years after the planet is thought to have formed. Scientists have speculated the first life may have evolved in shallow tide pools, freshwater ponds, freshwater or deep-sea hydrothermal vents, or even arrived on objects from space.
A cover article by Wolf and Professor Brian Toon on the topic appears in the July issue of Astrobiology. The study was funded by two NASA grants and by the National Science Foundation, which supports CU-Boulder’s Janus supercomputer used for the study.
Scientists have been trying to solve the faint young sun paradox since 1972, when Cornell University scientist Carl Sagan — Toon’s doctoral adviser at the time — and colleague George Mullen broached the subject. Since then there have been many studies using 1-D climate models to try to solve the faint young sun paradox — with results ranging from a hot, tropical Earth to a “snowball Earth” with runaway glaciation — none of which have conclusively resolved the problem.
“In our opinion, the one-dimensional models of early Earth created by scientists to solve this paradox are too simple — they are essentially taking the early Earth and reducing it to a single column atmospheric profile,” said Toon. “One-dimensional models are simply too crude to give an accurate picture.”
Wolf and Toon used a general circulation model known as the Community Atmospheric Model version 3.0 developed by the National Center for Atmospheric Research in Boulder and which contains 3-D atmosphere, ocean, land, cloud and sea ice components. The two researchers also “tuned up” the model with a sophisticated radiative transfer component that allowed for the absorption, emission and scattering of solar energy and an accurate calculation of the greenhouse effect for the unusual atmosphere of early Earth, where there was no oxygen and no ozone, but lots of CO2 and possibly methane.
The simplest solution to the faint sun paradox, which duplicates Earth’s present climate, involves maintaining roughly 20,000 parts per million of the greenhouse gas CO2 and 1,000 ppm of methane in the ancient atmosphere some 2.8 billion years ago, said Wolf. While that may seem like a lot compared to today’s 400 ppm of CO2 in the atmosphere, geological studies of ancient soil samples support the idea that CO2 likely could have been that high during that time period. Methane is considered to be at least 20 times more powerful as a greenhouse gas than CO2 and could have played a significant role in warming the early Earth as well, said the CU researchers.
There are other reasons to believe that CO2 was much higher in the Archean, said Toon, who along with Wolf is associated with CU’s Laboratory for Atmospheric and Space Physics. The continental area of Earth was smaller back then so there was less weathering of the land and a lower release of minerals to the oceans. As a result there was a smaller conversion of CO2 to limestone in the ocean. Likewise, there were no “rooted” land plants in the Archean, which could have accelerated the weathering of the soils and indirectly lowered the atmospheric abundance of CO2, Toon said.
Another solution to achieving a habitable but slightly cooler climate under the faint sun conditions is for the Archean atmosphere to have contained roughly 15,000 to 20,000 ppm of CO2 and no methane, said Wolf. “Our results indicate that a weak version of the faint young sun paradox, requiring only that some portion of the planet’s surface maintain liquid water, may be resolved with moderate greenhouse gas inventories,” the authors wrote in Astrobiology.
“Even if half of Earth’s surface was below freezing back in the Archean and half was above freezing, it still would have constituted a habitable planet since at least 50 percent of the ocean would have remained open,” said Wolf. “Most scientists have not considered that there might have been a middle ground for the climate of the Archean.
“The leap from one-dimensional to three-dimensional models is an important step,” said Wolf. “Clouds and sea ice are critical factors in determining climate, but the one-dimensional models completely ignore them.”
Has the faint young sun paradox finally been solved? “I don’t want to be presumptuous here,” said Wolf. “But we show that the paradox is definitely not as challenging as was believed over the past 40 years. While we can’t say definitively what the atmosphere looked like back then without more geological evidence, it is certainly not a stretch at all with our model to get a warm early Earth that would have been hospitable to life.”
“The Janus supercomputer has been a tremendous addition to the campus, and this early Earth climate modeling project would have impossible without it,” said Toon. The researchers estimated the project required roughly 6,000 hours of supercomputer computation time, an effort equal to about 10 years on a home computer.
h/t to Dr. Leif Svalgaard
@Janice Moore –
Leif’s 30 percent increase in solar luminosity is certainly more nearly correct than the 20 percent in the paper, or my entirely conjectural guess at it.
You may be interested to know that there are a great many stars in the Milky Way that are cirtually identical to the Sun in size, mass, temperature, age and energy output. However, there are certain to be fewer habitable planets around those stars than the stars themselves, And even if an otherwise Earth-like planet exists in the habitable zone, certain other conditions apply: the presence of the Moon and especially of Jupiter and Saturn has assuredly protected Earth from the sort of continual asteroidal bombardment that would have put a quick end to any advanced life, if not all life, by the gravity of the gas giants shepherding all the larger asteroids into orbits well away from Earth. There was a book out some years ago title “Rare Earth” which examined all the contingencies that had to be met before life could advance; unfortunately I do not recall the authors, but I have the book somewhere and if I find it I will post the info on it. This study drew the conclusion that the odds were that no more than one or two planets in a galaxy the size of tre Milky Way (a conclusion n that I can neither confirm or deny).
@lsvalgaard – I would offer one caution: stellar evolution, while welll established in the generality and generally agreed on, and certainly more precisely decfined than the evolution of life, like any science is still subject to new discoveries and refinements that might change some of the “:settled” theoretical understanding. “Settled” is, like “consensus,” a term that has no place in scientific discourse
lsvalgaard says:
“It most certainly is of CPU time. If they used only 100 cores all running at full speed, then in 60 hours they will have used 6000 hours of CPU time. But they don’t need a Janus to do that, 25 PCs each with 4 cores could do that as well in 60 hours, not 10 years.”
Actually, they probably couldn’t do it in 60 hours with 25 quad core PCs. There are a couple of reasons why.
With that kind of computing, signal transit times in the wires starts to become a significant factor. Massive core count supercomputers are generally laid out to minimize wire distances between cores to optimize signal lag. With a network of 25 PCs even if they are in the same physical room on the same LAN segment, signal lag will start to become significant vs the supercomputer.
The other issue is that managing that kind of process across multiple PCs entails more overhead than running a similar process across multiple cores on a single massive core supercomputer. With that much CPU time, the extra overhead starts to add up.
The difference might not be huge, but you won’t get quite the same performance operating over multiple networked PCs.
@Janice Moore –
My apologies: I didn’t complete my last sentence – the conclusion of it should be, ” . . . Milky Way that could sustain life long enough for advanced life such as on Earth could evolve; microbial life might develop on some but then soon be wiped out by asteroidal impacts.”. Please forgive the confusion.
Nothing but UNFCCC conform story telling?
The comment about methane in the atmosphere being 20-21 times as powerful as CO2 is nonsense. It shows that those making that comment have no understanding of reaction kinetics and heat & mass transfer (which are engineering subjects). Also, one should add that they have no experience with the design, operation and control of industrial processes where it is necessary to have some understanding of these subjects but then “climate science” is a pseudo-science in involving beliefs and politics.
Chad Wozniak says:
July 9, 2013 at 10:31 pm
“Settled” is, like “consensus,” a term that has no place in scientific discourse
All science is subject to revision, improvement, and refinement. There comes a point, though, where such refinements are of little import for the application of science to real life. E.g. General Relativity is not used in the calculation of parameters for the load on a bridge. Engineers use ‘settled’ science every day. An example from my own work: there has been vigorous debate about the magnitude of the solar magnetic field dragged out into space for times before spacecraft measurements. Different techniques by different groups using different proxies gave very discordant results. These differences have largely been resolved due to diligent research over the last decade and the various groups working on this problem have reached a consensus [and that is the right word here] as to what the values most likely have been for the last hundred years. Consensus here simply means that people no longer disagree on the issue [not that the consensus values necessarily are correct].
MattS says:
July 9, 2013 at 10:36 pm
The difference might not be huge, but you won’t get quite the same performance operating over multiple networked PCs.
That is why we have supercomputers. The ‘flaw’ in the report was to compare 6000 hours [2/3 year] to 10 years as that does not give a real measure of the power of the supercomputer. Probably they did the calculation in a few hours and that is what should be compared to 10 years.
Quite agree, now do we know with reasonable certainty the thickness/density/pressure of the atmosphere back then ?
what about the ammonia?
Janus is not that impressive. I have ten four-node machines in one rack with that kind of power. Of course, they each have a GPU card and a Fusion IO card and 512GB of RAM and sit on a 40Gbps backbone…
I’m confused as to why there is a paradox at all?
Sure if you average insolation and treat it as a constant across the globe you’d get the effective black body temp of earth dropping from today’s 255K to about 234K, which is pretty darn cold. But that’s my objection to averaging such a thing in the first place.
Take axial tilt and albedo out of it for simplicity. You’ve got a peak at high noon at the equator of 1368 w/m2 declining to 0 w/m2 at the poles. Drop insolation by 30% and you have a peak at high noon at the equator of 958 w/m2 declining to zero at the poles. My point being that the poles don’t change much and 958 w/m2 is still enough to keep the equatorial regions pretty toasty?
Gary, I already had a fine linear model of GCMs back in 2008. See the equation below Figure 2a in my Skeptic 14(1) article, here.
Our hydrogen based sun is similar to other hydrogen stars of the same size and age. Hydrogen fussion stars are going to behave to the same physical laws. Liken it to burning a match. They start the same and they end the same. Based on the billions of stars we see at various ages we conclude our star had a past that matches our observation of those other stars. It’s future can also be presumed. Earth is doomed. Period.
lsvalgaard says:
July 9, 2013 at 9:48 pm
Gary Hladik says:
July 9, 2013 at 8:45 pm
Can anyone explain to me why methane is so much more of a so-called “greenhouse gas” than carbon dioxide?
Roughly speaking the efficiency of a greenhouse gas depends on the number of different ways the molecules can vibrate, stretch, and shake. That is why N2 [with only two atoms] is not a GHG, H2O, O3, and CO2 [with three atoms] are GHGs, and Methane CH4 [with four atoms] is a very strong GHG, because it has many more ways to ‘shake and bake’, stretch and bend, etc.
This is correct so far as it goes but it doesn’t address the first part of Gary’s comment regarding the overlap of methane’s absorption spectrum with water.
“Methane is considered to be at least 20 times more powerful as a greenhouse gas than CO2…”. I’ve seen this claim before, but I see the IR absorption spectrum of methane partially overlaps water vapor’s spectrum. Can anyone explain to me why methane is so much more of a so-called “greenhouse gas” than carbon dioxide?”
Yes this study misses the point of the faint sun paradox. Nobody doubts that if you assume a highly sensitive atmosphere with positive feedbacks you can get a viable surface temperature. The problem is that as the sun warms you should get CO2 outgassing from the oceans followed by warmer temperatures today. Also we know there were periods billions of years ago when CO2 was much lower than 20ppt which sends models into icehouse conditions from which they cannot recover.
In summary: the actual paradox has not been addressed.
3 billion years ago the Earth was in an orbit closer to the sun. An inner solar system collision separated large chunk called ‘moon’ and under the impact the Earth drifted into more distant orbit.
If since the solar output increased by 20%, for the near constant insolation, using the power of 3 law, the orbit would have to move only by 6% further away, from 0.94AU to the present 1AU. No need for the CO2 ‘agent’.
So, way back when:
1. The Earth was much closer to the Sun,
2. Atmospheric pressure was much greater than today,
3. The Earth’s crust was much thinner and there was greater volcanic activity,
4. The Eart’h’s orbit was more, or less, elliptic and its tilt was different,
5. The earth was regularly being zapped by many more meteorites and asteroids,
6. The continents were a different shape, and finally
7. The composition of the Earth’s atmosphere was different.
Conclusion: this research is a pale, simplistic reflection of reality, just like all of today’s computer climate models.
The assumption made is that the atmosphere had the same extent umpty billion years ago as it has now, that is with a surface pressure of 1kg/cm2. At the current thickness the blanketing is good for 33-34C “greenhouse” warming. If you crank up the opacity by increasing the CO2 content you can increase the blanketing by the few degrees needed to compensate for lower solar luminosity. However, I notice that the modelers do not include convective transport and a CO2 rich atmosphere would be as convective as you can get and throw a spanner in your estimates.
The alternative is that the atmosphere simply was a bit thicker. At the same composition as now you need only 20% more, that is a surface pressure of 1.2 bar, to get the extra 6-8 degrees blanketing needed. This raises an interesting question about how the planet has lost just the right quantity of atmosphere over time to keep up with the Sun’s changes. Perhaps there is some feedback there that we don’t know anything about, yet.
Not sure if this has been mentioned yet, but in my Astrobiology unit a few years ago it was stated that CO2/methane had been discredited due to little evidence found in rocks. More likely reasons were: 1) with little landmass, the much larger oceans would absorb more energy; 2) fewer clouds would exist as most nuclei are formed by plants or animals; 3) neutrino researchers at KamLAND, suggest that radioactive decay may have been sufficient to warm the planet.
Cheers
Chad Wozniak July 9 10:31:
The paper says the Sun was 20% dimmer then; Mr Svalgaard says the Sun has brightened by 30%. They are (roughly) the same thing, depending where you start.
Janice Moore July 9 9:49:
You were right:WD40 is very important. It’s the answer to most things.
By the way – anybody – I should have thought that 80% luminosity would be warm enough in the Tropics. Am I missing something?
And the answer is … CO2!
A computer model which was programmed to find that CO2 warmed the planet, found that CO2 warmed the planet! This is what we call settled science.
The real conclusion to emerge from the dim sun paradox is something closer to James Lovelock’s Daisyworld hypothesis, a demonstration of the powerful effect of the biosphere to regulate the earth’s climate, and the negative feedbacks causing remarkable stability of climate over earth’s history. Warmth in the very early archaean period was provided by extreme volcanism and transuranic radioactive decay, possibly even natural nuclear reactors (where 235U achieved high enough concentrations, as it did even in much more recent times in Oklo in Africa where a U seam depleted in 235U was found together with evidence of natural fission for several million years).
Once bacterial life became established, especially photosynthesizing cyanobacteria, then the ingredients were present for climate stabilization by the biosphere itself. Planktonic cyanobacteria could for instance change albedo, as possibly could stromatolites.
But if you are a scientist interested in the question, this is all you have.
Then please don’t bother. Go find a real job that contributes to the well being of your fellow travelers on this planet. Pathetically stupid. Get a model, ramp up the co² parameters and, there you are, you have proof.
The only thing about this 3D model that in anyway is comparable to reality of the Earth 2.8bya that we can be sure of is that the Earth, is a SPHERE! The rest is pure simulation.
Ed Zuiderwijk says:
The alternative is that the atmosphere simply was a bit thicker. At the same composition as now you need only 20% more, that is a surface pressure of 1.2 bar, to get the extra 6-8 degrees blanketing needed. This raises an interesting question about how the planet has lost just the right quantity of atmosphere over time to keep up with the Sun’s changes. Perhaps there is some feedback there that we don’t know anything about, yet.
Smart comment. There is a relationship between the diameter of atmospheres and rotation rates.
http://tallbloke.wordpress.com/2013/01/24/tim-cullen-planetary-rotation-part-3-mars-earth-and-venus/
And a relationship between rotation rates and orbital distance. We are working on this and hope to complete a paper by next year.
Talking about the weather 3 billion years ago? Plus ca change, eh?
Still, what I *can* tell you for certain is that Britain in the 2020’s will be flooded repeatedly and catastrophically. How do I know this?
Because the UK government’s climate change advisory body has just predicted droughts for that period …
http://www.guardian.co.uk/environment/2013/jul/10/droughts-hot-dry-summers-england