From Harvard University Science: Scientists find signs of ‘snowball Earth’
Research suggests global glaciation 716.5 million years ago
Steve Bradt
Harvard Staff Writer
Geologists have found evidence that sea ice extended to the equator 716.5 million years ago, bringing new precision to a “snowball Earth” event long suspected of occurring around that time.
Led by scientists at Harvard, the team reports on its work in the latest edition of the journal Science . The new findings — based on an analysis of ancient tropical rocks in remote northwestern Canada — bolster the theory that the planet has, at times in the past, been covered with ice at all latitudes.
“This is the first time that the Sturtian glaciation [the name for that ice age] has been shown to have occurred at tropical latitudes, providing direct evidence that this particular glaciation was a ‘snowball Earth’ event,” said lead author Francis A. Macdonald, an assistant professor in Harvard’s Department of Earth and Planetary Sciences. “Our data also suggests that the Sturtian glaciation lasted a minimum of 5 million years.”
The survival of eukaryotic life — organisms composed of one or more cells, each with a nucleus enclosed by a membrane — throughout this period indicates that sunlight and surface water remained available somewhere on the surface of Earth. The earliest animals arose at roughly the same time, following a major proliferation of eukaryotes.
Even on a snowball Earth, Macdonald said, there would be temperature gradients, and it is likely that ice would be dynamic: flowing, thinning, and forming local patches of open water, providing refuge for life.
“The fossil record suggests that all of the major eukaryotic groups, with the possible exception of animals, existed before the Sturtian glaciation,” Macdonald said. “The questions that arise from this are: If a snowball Earth existed, how did these eukaryotes survive? Moreover, did the Sturtian snowball Earth stimulate evolution and the origin of animals?”
“From an evolutionary perspective,” he added, “it’s not always a bad thing for life on Earth to face severe stress.”
The rocks that Macdonald and his colleagues analyzed in Canada’s Yukon Territory showed glacial deposits and other signs of glaciation, such as striated clasts, ice-rafted debris, and deformation of soft sediments. The scientists were able to determine, based on the magnetism and composition of these rocks, that 716.5 million years ago they were located at sea level in the tropics, at about 10 degrees latitude.
“Because of the high albedo [light reflection] of ice, climate modeling has long predicted that if sea ice were ever to develop within 30 degrees latitude of the equator, the whole ocean would rapidly freeze over,” Macdonald said. “So our result implies quite strongly that ice would have been found at all latitudes during the Sturtian glaciation.”
Scientists don’t know exactly what caused this glaciation or what ended it, but Macdonald says its age of 716.5 million years closely matches the age of a large igneous province stretching more than 930 miles from Alaska to Ellesmere Island in far northeastern Canada. This coincidence could mean the glaciation was either precipitated or terminated by volcanic activity.
Macdonald’s co-authors on the Science paper are research assistant Phoebe A. Cohen; David T. Johnston, assistant professor of earth and planetary sciences; and Daniel P. Schrag, Sturgis Hooper Professor of Geology and Professor of Environmental Science and Engineering, all of Harvard. Other co-authors are Mark D. Schmitz and James L. Crowley of Boise State University; Charles F. Roots of the Geological Survey of Canada; David S. Jones of Washington University in St. Louis; Adam C. Maloof of Princeton University; and Justin V. Strauss.
The work was supported by the Polar Continental Shelf Project and the National Science Foundation’s Geobiology and Environmental Geochemistry Program.
This was published some years ago by the BBC through the open university in the UK. It’s a very poorly researched piece with the same sort of evidence as the current CO² debate.
As Erik has noted, this cooling episode is consistent with the theory laid out by Svensmark and Calder in “The Chilling Stars” that cosmic rays have a major effect on our climate. They enter our atmosphere and form condensation sites for low clouds. The clouds cause cooling by reflecting away sunlight. When our solar system passes through the spiral arms of our galaxy, which happens with a period of about 145 million years, we are subjected to a higher flux of cosmic rays because of greater exposure to supernovae. And sure enough the Earth goes through cooling periods every 145 million years. This Stuartian cooling fits the pattern, although it was very severe.
[Actually, we pass through spiral arms every 75 million years, though others have cited other numbers, including 30 million years as an explanation for the cycle of mass extinctions. 75 MYr is the most frequent cited number. – Astromod]
CO2: the god of the XXI century.
Well I don’t believe it because nowhere does it have qualifiers such as “likely” or “very likely”. These are imperitive scientific terms aren’t they? lol
Trying to discover what happened millions of years ago reminds me of the old Zen problem of how to get a goose out of a bottle without injuring the goose or breaking the bottle?
Things were very different then. Without sufficient factual evidence of what was happening 716.5 million years ago and the ‘context’ of the assumed event, the proposed hypothesis is mere speculation.
“Tens of millions of years” is a short period of time with respect to the past changes in the Earth’s atmospheric chemical composition. Carbon dioxide has been on a declining trend for about the past 148 million years. This ~148 million year trend is a small segment of the Earth’s more than 4,600 million year past. The Earth’s atmosphere was about 15 percent carbon dioxide in its early period, and life subsequently reduced those levels to below one percent over the past 2 billion years or more.
Carbon dioxide levels started to rise a very small amount about the time of the K-T boundary and the suspected 9 mile diameter asteroidal impact event. However, the present Quaternary Ice Age began about 30 million years ago (0.65 percent of the Earth’s existence), and the levels continued to decrease overall during this ice age. During the Karoo Ice Age of the Carboniferous, temperatures and carbon dioxide levels plummeted and then increased somewhat after the ice age. During the even earlier Andean-Saharan Ice Age of the Ordovician-Silurian, the temperature plummeted, but the carbon dioxide did not plummet until after the ice age and while the temperatures began to soar again. Nonetheless, carbon dioxide levels increased again, but not to their former levels.
Carbon dioxide can be expected to return to higher levels than today or even the levels which existed before the Quaternary Ice Age, because they did so after the past ice ages. If life is continuing to change and evolve the chemical composition of the atmosphere as before, perhaps carbon dioxide may never return to levels greater than 600-1000ppm until and unless aerobic life on Earth is extinguished. In any event, past history implies the end of this ice age should result in a substantial increase of carbon dioxide levels.
Ultimately, extraterrestrial events must extinguish most or virtually all life on the Earth. Without aerobic lifeforms to consume the carbon dioxide, the Earth’s continuing vulcanism must eventually accumulate substantial increases of carbon dioxide in the atmosphere.
Incidentally, I think the diagram should say “increased reflectivity” rather than “lowered reflectivity”.
Lower reflectivity means more heat absorbed and temperatures increasing.
While they talk about climate modeels, they don’t say CO2 and to be honest, I don’t see that CO2 has anything to do with it.
The conjecture is that volcanic activity may have either started or ended the glacial period.
We are supposed to be thinking here of something like Yellowstone park blowing up…. as I understand it, a one off volcanic event leaves a huge amount of ash and SOX in the atsmopshere at high altitudes which persists long after the event and blocks solar energy and we get a lot of cooling.
However, and I am assuming this is the thinking, if you get a massive caldera type eruption (the lid blowing off Yellowstone is the next such event but as I recall the event here was something much bigger) then you have huge amounts of ash etc in the atmosphere but continuing volcanic action below. In this case I would imagine the solar energy is mostly blocked and CO2 has litte to do with anything. The heat from volcanic activity would be ongoing and the heat released would be trapped due to that same ash etc. that is blocking solar energy; while solar energy isn’t getting in, volcanic energy isn’t getting out. In either case the effects of CO2 are going to be negligeable compared to the other effects.
So I can see the potential for volcanic activity being a possible factor eexcept that as the activity subsides, there is still the debris and particulates that persist in the atmosphere after the event blocking solar radiation. If the volcanic activity ceases, then there would be some major cooling. It all depends how hot it got, how long it lasted and so on. Of course, a transeint volcanic event wont’ produce much heating but a long term caldera type event? perhaps the oceean temperature were significantly elevated over time so that termination of volcanic activity would cool the planet but to a comfortable level?
PS I assume that during this time we would have also been subjected to meteor impacts…. its a long time frame and more debris in the system back then.
Perhaps some such event either triggered the ice ball (ejector in the atmosphere) or relieved it….. the thermal energy of the impact…. there are all sorts of mechanisms one could propose but the evidence would be slight.
It depends what evidence they have found or were looking for.
Meteor impact would be revealed the same way they inferered the Yucatan impact, from ejector material in the sediment, in this case either above or below. Meteor impact could also trigger volcanic events but was there any evidence of significant volcanic activity following Yucatan?
Did anyone look?
So far as I can see, the paper discloses evidence of the possible snowball earth and puts a date on it. It doens’t say CO2 has anything to do with anything. It spculates on possible triggers for the feezing and warming. There are lots of possibilities. The importance is that with a date, scientists know where to look in the geologocal records and evaluation of the strata imediately before and after is going to reveal clues to causal effects.
It is theorized that millions of years ago the solar irradiance for was lower than it is now, and this is plausible, based on astronomical observations of other stars in our galaxy. “Theoretical models of the Sun’s development suggest that 3.8 to 2.5 billion years ago, during the Archean period, the Sun was only about 75% as bright as it is today.” [Source: Wikipedia]. A slightly cooler sun itself (“Faint Young Sun” model) can contribute to an earlier cooler earth, however cannot explain “Snowball Earth” as recently as 0.7 billion years ago. What’s left? Rather than theorizing about a diminutive greenhouse gas (CO2), think catastrophic events!
– Massive volcano activity on the surface of the earth.
– Collision(s) between earth and asteroid(s) causing the atmosphere to be filled with massive amounts of light blocking & reflecting solid particles (dust).
– Substantial occlusion of solar radiation outside of the earth’s atmosphere, caused by massive quantities of comets, asteroid fields and /or a dense interstellar gas cloud traversing the solar system.
What we consider as “catastrophic” is business as usual for the universe, as the smoothness that we observe today in our solar system and elsewhere is in actuality an anomaly in terms of the long term processes that occur over millions of years. This idea has been advanced by Stephen Hawking in his discussion of the “Weak Anthropic Principle” in his book “A Brief History of Time”.
Nowhere in the article above did i find any reference to CO2 and while it may be expected as a result of volcanism, it doesn’t mean that it has a significant effect compared to the other factors. There must be something extreme going on to cause snowball earth.
It also doesn’t mean that just because we suspect some scientists and others of fudging AGW, we don’t throw out the whole of climate science.
A snowball earth lasting 5 million years is a major climate event and not just weather.
It seems quite reasonable that if you get ice extending far enough, sans other factors, then reflectivity will impact severely on the solar radiation budget.
The problem is to know the causes, what initiated it and what ended it. Major events must also have major causes.
That doesn’t have anything to do with AGW theories and however much we may think the theories of AGW are a crock, it doesn’t invalidate the entirety of climate science.
Like a lot of things, the snowball earth conceept has gone through some phases from theory to possibility to probability and now to some good evidence that it did happen and when it happened.
The sort of volcanic activity needed to have a significant causal effect is going to be massive. The impact of CO2 isn’t going to be a dominat effect and it says nothing about AGW.
I hate to be nitpicky but don’t I get a H/T for suggesting the article? Or did you find it on your own? Or did some one else suggest it first?
Reply: I dunno. ~ ctm
Dave Wendt (20:34:40) :
Am I correct in assuming that the illustration was not part of the PR, but added here.
The illustration was part of the PR.
The iceplanet Hoth 🙂
Thanks for posting this article! I find it very interesting.
Never before seen a drawing with the land-area as a belt around equator like that.
hehe.
No doubt such changes must have a huge impact on climate. Imagine all the big sea-currents we have today, gone.
No more heat transport from equator and towards the poles.
And a different level of cosmic rays from space. Yes, its nice on the planet today.Thats why we are here now. We fit in.
BUT, they should have skipped this very unscientific statement;
“…climate modeling has long predicted that if…”
They probably felt forced to put it in….otherwise, no grants?
I have invented a new concept;
“grant-forcing”, as opposed to water-vapout-forcing.
sorry; Water-vapour-forcing. (nit-picking)
Forgive me for not jumping on board a theory that begins with “for some reason it got colder”.
As CO2 has obtained the (I believe undeserved) status of “usual suspect” for any planetary warming event, I would really like to see if there are any other good theories for what might have caused of the end of the ‘Snowball Earth’ condition.
Nanny-Govt-Sucks
You need to do a rethink. Charles has it right.
The ocean floors are recycled at subduction zones. But from time to time slivers of ocean crust get incorporated, by complex faulting, into the edges of the continents. This is what most of the worlds Ophiolite Belts are made from (old oceanic crust). So there is plenty of evidence of ancient oceans that were way older than 200 myr. This has been confirmed by a multitude of independent lines of evidence. Its very tight science (rather unlike some parts of climate science). Further we can also tell how old these areas of ocean were using a variety of radiometric dating techniques. We can tell what types of fish and other sea creatures were about at the time via the associated fossil record. Open up a modern geology textbook for a general introduction.
CROSSPATCH and others,
We have hashed out on another post the effects of land masses at the poles. According to the geological record (Douglass McDougall, Frozen Earth) the snowball earth episode(s) occurred when the poles were land free.
Most people, especially climate scientists, equate polar ice build-up with cooling earth. In fact, the opposite it true. Polar ice actually reduces the rate at which the earth loses heat. That is the key… the RATE of cooling. Ask yourself this question. Which pole is currently cooling the earth more, the arctic or the antarctic? The answer is the arctic. Sure, the antarctic is cooler, which is why there is so much confusion. When ice forms on the arctic, not as much heat can be radiated into space, or transferred to the atmosphere then radiated into space. The temperature at the surface is cooler, of course, with ice formation over the water, but this is not the important piece. The net heat balance of the entire planet is maintained with this insulating cap over the warmer water. Please remember that polar ice does not affect the albedo of the earth significantly, because of the tiny sun angle. Just think, how much sun gets reflected off the arctic ice in the winter? Zero. How about in the summer? Very little. The ice at the equator has a much more significant impact on the albedo, and represents a net heat loss. This is why paleo climatologists “blame” the current ice age on the raising of the Himalayas.
You alluded to these ideas in your post, CROSSPATCH, so I think you will have no problem grasping it. The same cannot be said for the head of the Climate department at my local university. We have gone round and round on this topic, as well as others like positive feedback loops and other ideas that violate the temperature record of Earth’s past.
(rant): it should be a requirement for all climate scientists to take (and more importantly pass) courses in thermodynamics and engineering process control.
The CO2 Theory in this study is hogwash.
If the theory were that possibly a meteor struck the ocean and created massive evaporation and water vapour, then I could buy that.
Our solar system travels through space at a very high rate of speed and our planet rotates in front and sides of the sun. This would make our tiny planet a target 8 months of the year. The distance changes of the sun to planet of our orbit is not ellipical like scientists think. The mass of the sun is constantly moving forward and as we rotate, our planet catches up with the sun. When our plant is in front of the sun, the sun is moving closer to our planet.
So, if these scientists are correct, our CO2 levels are at the highest in recorded history….hmmm.
Almost all the continents were locked together over the south pole in Supercontinents Rhodinia and Pannotia at the time. The climate scientists do their best to ignore Continental Drift.
There were two extreme Snowball periods around 715 million years ago and again at 635 million years ago (and at least two others at 2.4 and 2.2 billion years ago).
What would happen if all the continents were locked together where Antarctica is now.
So much ice builds up and spreads out across all the land which is now connected that Albedo increases to close to 0.5 (50% of the sunlight is reflected versus 30% today). That is enough to drop the average temperatures to -20C, just the amount needed to freeze over most of the Earth except for the tropics.
http://www.marathon.uwc.edu/geography/100/rad-te1.gif
Snowball ends when continental drift breaks apart the Supercontinent and the continents move away from the pole.
http://en.wikipedia.org/wiki/File:SnowballGeography.gif
http://www.meteo.mcgill.ca/~tremblay/Courses/ATOC530/Hyde.et.al.Nature.2000.pdf
CO2 levels were only about 12,000 ppm at the end of the last Snowball 635 million years ago and only about 6,000 ppm during the previous Snowball 715 million years ago (while the GHG theory would have required at least 286,000 ppm or 29% of atmosphere as CO2 to end the Snowballs – or even 2 or 3 times higher than this).
http://www.snowballearth.org/Bao08.pdf
Complete nonsense!
James Ussher (1581-1656) Archbishop of Ireland sorted this out a very long time ago.
The Earth was created on October 23rd, 4004 BC.
So no snowballs, just AGW.
I’m not sure we know enough about how snow, ice and frost melt, there are definitely other factors than just air temperatures involved; insolation, wind speed and relative humidity seem to be big factors. Crediting CO2 seems a stretch, hoarfrost captures a lot of photons and 5 million years is a long time for subtle effects to accumulate.
Bill Illis (05:40:08)
The speculation has omitted one gigantic event in the evolution of the atmosphere, the great oxygen catastrophe or Great Oxygenation Event (GOE) of the Huronian Ice Age. The role of oxygen, chemical evolution of the lithospshere and atmosphere, and aerobic lifeforms are being largely disregarded in favor of a far less influential carbon dioxide yet vital chemical component.
Some elements of the hypothesis are and must inherently be speculative. Nonetheless, substantial parts of this hypothesis and similar hypotheses are supported by a large array of well established factual evidence. Dropstones and tilllites in the geological strata indicate glacial conditions. Banded Iron Formations (BIF) provide indications of oxygenation events. Paleomagentic evidence while difficult to obtain without a potential for errors does provide at least one geological formation without the possible errors. Geochemical signatures provide rock solid evidence. Radioisotopic ratios for carbon provide strong indicators. While the evidence is still in the incomplete and early stages of the investigation, what is already known cannot be dismissed as only speculation, because a significant body of the evidence is not speculation at all. Severe ice ages lasting hundreds of millions of years instead of the more recent tens of millions of years certainly did occur. The extent to which those monumental ice ages resulted in a true Snowball Earth or a quasi-Snowball Earth is uncertain, but the research is still in the early stages which can hugely benefit one way or the other from further research and discoveries in the future.