Note: I’m going to leave this as a sticky “top post” for a day or so. new stories appear below.
Nigel Calder asks us to republish this post for maximum exposure. He writes:
Today the Royal Astronomical Society in London publishes (online) Henrik Svensmark’s latest paper entitled “Evidence of nearby supernovae affecting life on Earth”. After years of effort Svensmark shows how the variable frequency of stellar explosions not far from our planet has ruled over the changing fortunes of living things throughout the past half billion years. Appearing in Monthly Notices of the Royal Astronomical Society, it’s a giant of a paper, with 22 figures, 30 equations and about 15,000 words. See the RAS press release at http://www.ras.org.uk/news-and-press/219-news-2012/2117-did-exploding-stars-help-life-on-earth-to-thrive
By taking me back to when I reported the victory of the pioneers of plate tectonics in their battle against the most eminent geophysicists of the day, it makes me feel 40 years younger. Shredding the textbooks, Tuzo Wilson, Dan McKenzie and Jason Morgan merrily explained earthquakes, volcanoes, mountain-building, and even the varying depth of the ocean, simply by the drift of fragments of the lithosphere in various directions around the globe.
In Svensmark’s new paper an equally concise theory, that cosmic rays from exploded stars cool the world by increasing the cloud cover, leads to amazing explanations, not least for why evolution sometimes was rampant and sometimes faltered. In both senses of the word, this is a stellar revision of the story of life.
Here are the main results:
- The long-term diversity of life in the sea depends on the sea-level set by plate tectonics and the local supernova rate set by the astrophysics, and on virtually nothing else.
- The long-term primary productivity of life in the sea – the net growth of photosynthetic microbes – depends on the supernova rate, and on virtually nothing else.
- Exceptionally close supernovae account for short-lived falls in sea-level during the past 500 million years, long-known to geophysicists but never convincingly explained..
- As the geological and astronomical records converge, the match between climate and supernova rates gets better and better, with high rates bringing icy times.
Presented with due caution as well as with consideration for the feelings of experts in several fields of research, a story unfolds in which everything meshes like well-made clockwork. Anyone who wishes to pooh-pooh any piece of it by saying “correlation is not necessarily causality” should offer some other mega-theory that says why several mutually supportive coincidences arise between events in our galactic neighbourhood and living conditions on the Earth.
An amusing point is that Svensmark stands the currently popular carbon dioxide story on its head. Some geoscientists want to blame the drastic alternations of hot and icy conditions during the past 500 million years on increases and decreases in carbon dioxide, which they explain in intricate ways. For Svensmark, the changes driven by the stars govern the amount of carbon dioxide in the air. Climate and life control CO2, not the other way around.
By implication, supernovae also determine the amount of oxygen available for animals like you and me to breathe. So the inherently simple cosmic-ray/cloud hypothesis now has far-reaching consequences, which I’ve tried to sum up in this diagram.
By way of explanation
The text of “Evidence of nearby supernovae affecting life on Earth” is available via ftp://ftp2.space.dtu.dk/pub/Svensmark/MNRAS_Svensmark2012.pdf The paper is highly technical, as befits a professional journal, so to non-expert eyes even the illustrations may be a little puzzling. So I’ve enlisted the aid of Liz Calder to explain the way one of the most striking graphs, Svensmark’s Figure 20, was put together. That graph shows how, over the past 440 million years, the changing rates of supernova explosions relatively close to the Earth have strongly influenced the biodiversity of marine invertebrate animals, from trilobites of ancient times to lobsters of today. Svensmark’s published caption ends: “Evidently marine biodiversity is largely explained by a combination of sea-level and astrophysical activity.” To follow his argument you need to see how Figure 20 draws on information in Figure 19. That tells of the total diversity of the sea creatures in the fossil record, fluctuating between times of rapid evolution and times of recession.
The count is by genera, which are groups of similar animals. Here it’s shown freehand by Liz in Sketch A. Sketch B is from another part of Figure 19, telling how the long-term global sea-level changed during the same period. The broad correspondence isn’t surprising because a high sea-level floods continental margins and gives the marine invertebrates more extensive and varied habitats. But it obviously isn’t the whole story. For a start, there’s a conspicuous spike in diversity about 270 million years ago that contradicts the declining sea-level. Svensmark knew that there was a strong peak in the supernova rate around that time. So he looked to see what would happen to the wiggles over the whole 440 million years if he “normalized” the biodiversity to remove the influence of sea-level. That simple operation is shown in Sketch C, where the 270-million-year spike becomes broader and taller. Sketch D shows Svensmark’s reckoning of the changing rates of nearby supernovae during the same period. Let me stress that these are all freehand sketches to explain the operations, not to convey the data. In the published paper, the graphs as in C and D are drawn precisely and superimposed for comparison.
There are many fascinating particulars that I might use to illustrate the significance of Svensmark’s findings. To choose the Gorgon’s story that follows is not entirely arbitrary, because this brings in another of those top results, about supernovae and bio-productivity.
The great dying at the end of the Permian
Out of breath, poor gorgon? Gasping for some supernovae? Named after scary creatures of Greek myth, the Gorgonopsia of the Late Permian Period included this fossil species Sauroctonus progressus, 3 metres long. Like many of its therapsid cousins, near relatives of our own ancestors, it died out during the Permo-Triassic Event. Source: http://en.wikipedia.org/wiki/Gorgonopsia
Luckiest among our ancestors was a mammal-like reptile, or therapsid, that scraped through the Permo-Triassic Event, the worst catastrophe in the history of animal life. The climax was 251 million years ago at the end of the Permian Period. Nearly all animal species in the sea went extinct, along with most on land. The event ended the era of “old life”, the Palaeozoic, and ushered in the Mesozoic Era, when our ancestors would become small mammals trying to keep clear of the dinosaurs. So what put to death our previously flourishing Gorgon-faced cousins of the Late Permian? According to Henrik Svensmark, the Galaxy let the reptiles down.
Forget old suggestions (by myself included) that the impact of a comet or asteroid was to blame, like the one that did for the dinosaurs at the end of the Mesozoic. The greatest dying was less sudden than that. Similarly the impressive evidence for an eruption 250 million years ago – a flood basalt event that smothered Siberia with noxious volcanic rocks covering an area half the size of Australia – tells of only a belated regional coup de grâce. It’s more to the point that oxygen was in short supply – geologists speak of a “superanoxic ocean”. And there was far more carbon dioxide in the air than there is now.
“Well there you go,” some people will say. “We told you CO2 is bad for you.” That, of course, overlooks the fact that the notorious gas keeps us alive. The recenty increased CO2 shares with the plant breeders the credit for feeding the growing human population. Plants and photosynthetic microbes covet CO2 to grow. So in the late Permian its high concentration was a symptom of a big shortfall in life’s productivity, due to few supernovae, ice-free conditions, and a lack of weather to circulate the nutrients. And as photosynthesis is also badly needed to turn H2O into O2, the doomed animals were left gasping for oxygen, with little more than half of what we’re lucky to breathe today.
When Svensmark comments briefly on the Permo-Triassic Event in his new paper, “Evidence of nearby supernovae affecting life on Earth,” he does so in the context of the finding that high rates of nearby supernovae promote life’s productivity by chilling the planet, and so improving the circulation of nutrients needed by the photosynthetic organisms.
Here’s a sketch (above) from Figure 22 in the paper, simplified to make it easier to read. Heavy carbon, 13C, is an indicator of how much photosynthesis was going on. Plumb in the middle is a downward pointing green dagger that marks the Permo-Triassic Event. And in the local supernova rate (black curve) Svensmark notes that the Late Permian saw the largest fall in the local supernova rate seen in the past 500 million years. This was when the Solar System had left the hyperactive Norma Arm of the Milky Way Galaxy behind it and entered the quiet space beyond. “Fatal consequences would ensue for marine life,” Svensmark writes, “if a rapid warming led to nutrient exhaustion … occurring too quickly for species to adapt.”
One size doesn’t fit all, and a fuller story of Late Permian biodiversity becomes subtler and even more persuasive. About 6 million years before the culminating mass extinction of 251 million years ago, a lesser one occurred at the end of the Guadalupian stage. This earlier extinction was linked with a brief resurgence in the supernova rate and a global cooling that interrupted the mid-Permian warming. In contrast with the end of the Permian, bio-productivity was high. The chief victims of this die-off were warm-water creatures including gigantic bivalves and rugose corals.
Why it’s tagged as “astrobiology”
So what, you may wonder, is the most life-enhancing supernova rate? Without wanting to sound like Voltaire’s Dr Pangloss, it’s probably not very far from the average rate for the past few hundred million years, nor very different from what we have now. Biodiversity and bio-productivity are both generous at present.
Svensmark has commented (not in the paper itself) on a closely related question – where’s the best place to live in the Galaxy?
“Too many supernovae can threaten life with extinction. Although they came before the time range of the present paper, very severe episodes called Snowball Earth have been blamed on bursts of rapid star formation. I’ve tagged the paper as ‘Astrobiology’ because we may be very lucky in our location in the Galaxy. Other regions may be inhospitable for advanced forms of life because of too many supernovae or too few.”
Astronomers searching for life elsewhere speak of a Goldilocks Zone in planetary systems. A planet fit for life should be neither too near to nor too far from the parent star. We’re there in the Solar System, sure enough. We may also be in a similar Goldilocks Zone of the Milky Way, and other galaxies with too many or too few supernovae may be unfit for life. Add to that the huge planetary collision that created the Earth’s disproportionately large Moon and provided the orbital stability and active geology on which life relies, and you may suspect that, astronomically at least, Dr Pangloss was right — “Everything is for the best in the best of all possible worlds.”
Don’t fret about the diehards
If this blog has sometimes seemed too cocky about the Svensmark hypothesis, it’s because I’ve known what was in the pipeline, from theories, observations and experiments, long before publication. Since 1996 the hypothesis has brought new successes year by year and has resisted umpteen attempts to falsify it.
New additions at the level of microphysics include a previously unknown reaction of sulphuric acid, as in a recent preprint. On a vastly different scale, Svensmark’s present supernova paper gives us better knowledge of the shape of the Milky Way Galaxy.
A mark of a good hypothesis is that it looks better and better as time passes. With the triumph of plate tectonics, diehard opponents were left redfaced and blustering. In 1960 you’d not get a job in an American geology department if you believed in continental drift, but by 1970 you’d not get the job if you didn’t. That’s what a paradigm shift means in practice and it will happen sometime soon with cosmic rays in climate physics.
Plate tectonics was never much of a political issue, except in the Communist bloc. There, the immobility of continents was doctrinally imposed by the Soviet Academy of Sciences. An analagous diehard doctrine in climate physics went global two decades ago, when the Intergovernmental Panel on Climate Change was conceived to insist that natural causes of climate change are minor compared with human impacts.
Don’t fret about the diehards. The glory of empirical science is this: no matter how many years, decades, or sometimes centuries it may take, in the end the story will come out right.
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For those who would doubt our cosmic connections, Svenmark’s work and Calder’s article reminds me to remind you of this well known quote:
The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff. – Carl Sagan
Super-Novae decoded:
http://www.holoscience.com/news.php?article=re6qxnz1#top
“Evidence of nearby supernovae affecting life on Earth,” he does so in the context of the finding that high rates of nearby supernovae promote life’s productivity by chilling the planet, and so improving the circulation of nutrients needed by the photosynthetic organisms.”
Classic negative feedback that governs (in the mechanical sense a la Willis Eschenbach) our planets comparatively stable temperature and atmospheric chemistry.
Only thing Nigel Calder: your heroes of the 1960s regarding plate tectonics (a dental mechanic’s term?) – invented the term itself to hide the more poetic term ‘continental drift’ which was ignominiously buried with its propounder Wegener, who was thoroughly vilified by the elite of the geological professsion 40 years before the middle 1960s. Evidence for this heresy began to mount, first among South African geologists who identified similarities in the geology and fossil species in South America. Even diamonds were found in Brazil before finding them in Africa. Finally it could no longer be ignored.
Willis Eschenbach says:
April 25, 2012 at 12:30 am
“… so sue me.”
I wasn’t aware that you had gobs and gobs of money. And if not, what’s the point of sueing you?
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Personally, I thank you, Willis, and Leif and others for the contributions you make in these postings. And Anthony for providing the place to do it. And those doing the real-time moderating. So I’m a little confused by how the world works. I can live with that. It is a beautiful day for feeding the horses, digging a hole for a new post and gate, and watching my cherry trees blossom. I’ll catch up with y’all when the Sun goes down.
adolfogiurfa says:
April 25, 2012 at 9:15 am
Super-Novae decoded
That people in this day and age can fall for this nonsense is a demonstration of the low science- literacy and gullibility of the populace at large. Sad, indeed. Perhaps you can get tallbloke to sign on to your faith, it seems he will believe anything weird, so you can continue your indulgency over there.
Steve from Rockwood (5:53 am), sophocles, Willis . . .
A little background reading:
How the Isthmus of Panama Put Ice in the Arctic
Drifting continents open and close gateways between oceans and shift Earth’s climate
http://www.whoi.edu/cms/files/dfino/2005/4/v42n2-haug_2272.pdf
Also, see the quote provided by Gail Combs @8:09 pm.
Learning a lot from Dr. Svalgaard’s comments. Thank you!
Reblogged this on Bohls Neighborhood Talk and commented:
Thisis a reblog.
Leif Svalgaard says:
April 25, 2012 at 5:11 am
Many thanks as always, Leif. My point is that the claim, that the sky should be a featureless grey at Tev scales, which has been believed to be true up to now, has been shown not to be true. This indicates that our understanding of the processes controlling the generation and evolution of cosmic rays is not complete.
In addition, there is the unanswered question … where are the supernova remnants? Theory and models indicate that we should see lots of them in the Milky Way. We don’t see them. This indicates that our understanding of the processes controlling supernovas is not complete.
Both of those bear on Svensmark’s work, which rests heavily on the assumption that we do understand those processes, and not only that, but that we understand them well enough to model them accurately over a half billion years …
w.
L. Louis Lancaster: The controversy surrounding climate change is being exploited by those industries most affected by any regulations to reduce industrial emissions. Of course those industries will work to keep the controversy alive in order to stall those regulations.
That is only part of the story. Other parts of the story include the companies who stand to gain great rewards from redirecting investment towards reducing CO2: Siemens and GE and other manufactureres of wind turbines and PV panesl; Archer Daniels Midland and other industrial agriculture who manufacture biofuels. These companies invest a lot of money in promoting the idea that AGW must be halted and reversed. Even fossil fuel companies promote the idea of AGW to gain subsidies for new ventures and promote their brands in the fossil fuel market (e.g. BP calling itself “green” to boost its fuel sales.)
What I’m impressed with is the fact that the Wilson Cloud Chamber, which was used to detect GCR and other particles in 1911 (101st birthday nearby?) didn’t impress the Luddites that are so negative on Svensmark’s theory.
I see a lot of querying of the details and timescales, etc. All we have to really do is keep track of the GCR flux now and see if we can see what happens. Svensmark may not be right on as regards geological, biological and extra-terrestrial events – but he may be in terms of the effect of GCRs on climate.
I would like to comment on the process here. Me, I’d like nothing better than if Svensmark’s work were shown to be 100% correct. The idea that cosmic rays affect the climate is one that could be true. By that, I mean that there is a proposed mechanism which doesn’t require any new science, and that doesn’t break any of scientific laws.
In fact, I have said in the past that cosmic rays are a possible mechanism for long-term drift of what I see as a pretty tightly governed system.
But I guess my head works differently than most folks here. For me, the theories that we should examine the most closely, the theories that we should hold up in the most unfavorable light to look for flaws, are precisely those that we would like very much to be true.
Steven Mosher commented on this issue earlier in the thread, saying:
But people misunderstood him, saying if Mann would only show his work and his data that he wouldn’t get attacked. That’s not Mosh’s point.
His point is that we should investigate things we would like to be true as thoroughly and with the same energy as we investigate things we believe to be false.
I couldn’t agree more. Svensmark has made what are to me a number of dubious choices, such as the choice of the WEBDA database, that he has neither justified nor explained. His claimed correlations are very dependent on those choices, including such things as the choices for the parameters of the decay function. If those decay parameters are changed even slightly, his claimed correlation disappears. The same is true about his curious choice of an 8 million year bin size. It greatly exaggerates the period 16-8 million years ago, because it happens to coincide with a clump of cluster formation. Things look quite different when you use say a 1 million year bin size.
How do I know that? Well … I went and looked at it. Boring stuff, calculate the logarithms of the ages you need, then sit there with the WEBDA open cluster search tool, one Myr period after another … but that’s the kind of dull grunt work that science requires, and I don’t have any graduate students to put on the task … here’s that result:
See, for Svensmark’s theory to pan out, he needs a big bump in the number of supernovas about 10 Myr ago. If you use 8 million year (Myr) bins, the 8-16 Myr bin gets the whole clump, and there’s the big bump his theory depends on … whereas if you used say 12 Myr bins, that doesn’t happen, the first bin is the largest.
Now, it may be that there are valid reasons for choosing 8 Myr bins. But at a minimum, Svensmark needs to investigate the effects of his various choices of parameters. Steve Mosher made this point above regarding Svensmarks choice of the WEBDA database, saying:
The same is true with his graphs that claim to show correlations. I digitized his graph and show above that the correlation between supernovas and paleosol CO2 is quite poor, R^2 = 0.17 … but Svensmark never even calculates the R^2 value, he just shows a pretty picture.
Now, please be clear that I don’t think Svensmark is setting out to fool people. I think instead that he is an honest scientist who is fooling himself. At each turn and each choice he is selecting, consciously or unconsciously, the most favorable method or the best parameter setting … but when you have a host of free parameters and open choice of methods, that can add up without you knowing it to the point where the whole edifice is built on sand.
Like I said … I’d like very much for his claim to be true, which is why I am looking so closely at it.
All the best,
w.
L. Louis Lancaster said “the steps suggest to address climate change are the same ones that would reduce the toxic and particulate emissions that degrade” our environment. I call BS. Reducing CO2 emissions has NOTHING to do with reducing toxic and particulate emissions. The two types of emissions, and the methods and costs involved in reducing them, are NOT the same. Further, since more CO2 is good for green plants, especially food crops, it could argued that reducing CO2 emissions is bad for the environment. Learn a little science. Conflating CO2 emissions with “toxic and particulate emissions” is typical eco-loon ignorance.
This is brilliant. Truly brilliant.
Leif Svalgaard says:
April 25, 2012 at 6:33 am
Svensmark is looking for supporting evidence for the faltering notion that cosmic rays control the climate. Faltering because solar activity at present is on par with that of a century ago, while the climate is not.
This is a specious argument. Solar activity has *suddenly fallen* to levels it was at a century ago. The heat built up in the ocean since ~1935 by higher than average levels of solar activity over 7 decades until 2003 will not dissipate overnight.
Leif Svalgaard says:
April 25, 2012 at 9:25 am
adolfogiurfa says:
April 25, 2012 at 9:15 am
Super-Novae decoded
http://www.holoscience.com/news.php?article=re6qxnz1#top
That people in this day and age can fall for this nonsense is a demonstration of the low science- literacy and gullibility of the populace at large. Sad, indeed. Perhaps you can get tallbloke to sign on to your faith, it seems he will believe anything weird, so you can continue your indulgency over there.
Here you go again with this ‘faith’ thing. You have ‘faith’ in the standard gravity only explanation. Adolfo thinks it inadequate. I agree with him, and remain open to alternative explanations. You are not, because you are sure you know what can be excluded. How wrong you are.
Willis Eschenbach says:
April 25, 2012 at 10:11 am
Many thanks as always, Leif. My point is that the claim, that the sky should be a featureless grey at Tev scales, which has been believed to be true up to now, has been shown not to be true.
Not TeV scales, but a thousand times less energetic, GeV. There are too few TeV particles to have any effect on anything. On the question, where are the SN Remnants, here is a catalog of known ones observed in X-rays: http://hea-www.cfa.harvard.edu/ChandraSNR/snrcat_gal.html
As SN Remnants expand with time and get lost in the general background these are all ‘young’.
The website also notes: “Several broken features have been fixed recently (March 2010) and since then 32 new objects have been added.”. I don’t know if those are in the catalog, but presumably they are. Anyway, I count about 100, which with 3 per century would cover a time span of 3300 years, but to be observable in X-ray they have to be young as the flux decline rapidly with age. The estimated number of observed SN Remnants in the Galaxy is 250 [ http://www.centauri-dreams.org/?p=1871 ]. The life time of a remnant is variously quoted between 30,000 [Braun,Goss & Lyne 1989] and 1,000,000 years which with 3 per century would mean a number between 900 and 30,000. But the vast majority of these are not observable because of their faintness, see e.g. http://dspace.rri.res.in/bitstream/2289/3315/17/Chapter%206.pdf
Their radio and x-ray emission really depends on the pulsar at the center which is powering the emission. The pulsars have a spin-down time of only a few thousand years, so perhaps there is no problem. I don’t see the issue rising to the level where people can say: “we don’t know anything”, “our theories and models are all wrong”, and other assorted nonsense.
Looking for SN remnants? Looking where? If the blast occured 100 million years ago and gave the remnant a one tenth C boost in a particular direction ( not unreasonable for such a situation) it would now be 10 million light years away from its point of detonation. I believe this would give it escape velocity from our galaxy. Use 10 million years and you still have 1 million light years of travel from point of origin. What happens to any nebula that may have been generated after this much time has passed? What about the regular proper motion of the solar system and extra solar “events” within the galaxy during that time? The times and the distances involved in this exercise make it very interesting to think about but I believe very difficult to find evidence one way or the other.
tallbloke says:
April 25, 2012 at 12:02 pm
This is a specious argument. Solar activity has *suddenly fallen* to levels it was at a century ago.
No, it has declined steadily for some 25 years.
The heat built up in the ocean since ~1935 by higher than average levels of solar activity over 7 decades until 2003 will not dissipate overnight.
The time constant has been estimated by several people to be less than a solar cycle.
Here you go again with this ‘faith’ thing. You have ‘faith’ in the standard gravity only explanation. Adolfo thinks it inadequate. I agree with him, and remain open to alternative explanations. You are not, because you are sure you know what can be excluded. How wrong you are.
The ‘gravity only’ is specious. One could contrast that with the ‘EU only’. I would say that both Adolfo and you qualify to belong to the category of believers I mentioned. Now, there is nothing wrong in having such beliefs as long as you don’t confuse them with science. There are good physical reasons for excluding things, but if one rejects those, then, of course everything is game: “if one knows nothing, everything is possible”.
There is a lot of criticism of using the single database for estimating GCR levels over time here, but it does also mention that this was (somewhat) corroborated against Iron meteorites (p5, paragraph 2). I looked at a few papers relating to this, I’m no expert, but it does seem to be a fairly well explored area. Here is an interesting rebuttal to a criticism of that science, interesting in that it answers some of the questions I had about it. Specifically how it all works : ).
http://www.phys.huji.ac.il/~shaviv/ClimateDebate/RahmstorfDebate.pdf
Not saying that settles anything of course, but it does seem a lot more empirical and measurement based than your typical climate papers. Even the three databases, while certainly different, are ultimately based on measurements that can be taken again if need be. I understand there is reconstruction going on, based on theories that can change, but at least the initial data is less controversial. It isn’t surprising then that there is broad agreement in different datasets, without needing to calibrate them against each other.
Impacts, volcanism and mass extinction, random coincidence or cause and effect?
http://instruct.uwo.ca/earth-sci/083f/kellerkt.pdf
Willis Eschenbach says:
April 25, 2012 at 11:34 am
You are doing what I hoped would happen. My central worry in my post at April 24, 2012 at 5:22 pm which was later followed up on by Steven Mosher at April 24, 2012 at 7:48 pm was that Svensmark’s correlation was an artifact of his choices and methods of calculation. His calculations have to be verified, by others, by different kind of calculations, by using alternative datasets. If some signal is there, it will come out in the end. Great work.
Could there be an ionizing radiation effect? More supernovae = more cosmic irradiation = more genetic point mutations in living organisms, faster speciation as a result?
Willis Eschenbach: I digitized his graph and show above that the correlation between supernovas and paleosol CO2 is quite poor, R^2 = 0.17
There is no R^2 value that is an absolute standard. Lots of things that prolong life, like calorie restriction, exercise, and taking aspirin, have quite small R^2 values (percent of life-span “explained”), yet are important For a system as noisy and poorly measured as past climate oscillation, 0.17 is too large to neglect. It requires confirmation, of course.
Just when I’d begun to stop missing my old PC game called SimEarth, along comes this report and Nigel’s earth cycles graphic. The idea that sporadic bursts of ionizing energy from local supernovas could trip the switch for long-term global environmental change and the resulting well-defined geologic eons, periods and/or epochs makes more sense than thinking the odd asteroid/comet impact or even our own sun with it’s apparently regular but short-term cycles could, on their own, release sufficient energy to trigger such changes.
“Gaea’s Biorhythm Chart” – Would like to see those trying to quantify the ponderously complex dynamics involved in major global changes (e.g., extinction events, ice ages) overlay the estimated dates and effects of known asteroid/comet impacts, prehistoric mega-volcano eruptions as well as the solar cycle, compensating for the lag between such dramatic assaults and any significant prehistoric environmental change to see what if any correlation can be seen. Perhaps all 3 assaults have to occur within a relatively short period to trip the big switch (Era), 2 for a Period, 1 for an Epoch?
To any who seek to downplay the devastating impact man’s insatiable consumption and pollution has had and will have on the biosphere in the short term to stonewall going green or justify the status quo continuation of our locust-like despoiling of the planet, I have some swampland I’d like to unload cheap before it completely submerges.
Willis Eschenbach says:
April 24, 2012 at 2:40 pm
………………..But a recent paper “Relative sea-level fall since the last interglacial stage: Are coasts uplifting worldwide?“, evaluated some 890 of the paleo-shorelines worldwide.
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Well not around here along the Australian Sydney coastline Willis. We have “drowned” drainage valleys here of several hundred feet that during the post Triassic had cut their way through the thick layers of Triassic sandstone and shale. All the coastal headlands have had progressive erosion of those layers by the sea. So coastal uplift it not global by any means as suggested in your reference.