Traducido por Angela Carosio
“en este año hubo un temido presagio. El sol dio su luz sin brillo…y parecía como un sol de eclipse, pues los rayos de luz no eran claros.”
Esta cita de Procopius de Cesarea es igual a las de otras fuentes alrededor del mundo y señala un fenómeno climático, generalmente conocido como niebla seca que viene acompañado por un verano frío, el fracaso de las cosechas y otra serie de problemas. En una serie de TV, libros y artículos en la prensa se sugirieren, como posibles causas, erupciones volcánicas, cometas y otras catástrofes. Pero esta semana se publicó un nuevo artículo en GRL que podría ofrecer una respuesta definitiva…
Es bien sabido que los anillos de crecimiento de los árboles (como el de la fotografía, proveniente de Arizona) generalmente muestran un anillo de crecimiento extremadamente pequeño para el año AD 536 (éste se puede contar hacia atrás desde el anillo marcado como AD 550.) En efecto, si observamos las anomalías de toda una serie de construcciones de anillos de crecimiento, este evento se destaca como excepcional en los últimos 2000 años, junto con los años 1601 y 1815 (ambos conocidos por erupciones volcánicas).
Fig. 1: Promedio de los componentes de alta frecuencia en 7 reconstrucciones de anillos de crecimiento de árboles del norte de Europa, por Larsen et al, 2008. El filtrado asegura que las incertidumbres en las tendencias a largo plazo (que no son importantes en este contexto) no confundan los resultados.
Estos datos coinciden con las fuentes escritas. Sin embargo, la búsqueda de una causa para AD 536 siempre ha estado plagada de problemas de cronología. El intento de asociar este evento con una erupción volcánica en las muestras de corazón hielo Dye3 de Groenlandia se desplomó cuando dicha cronología fue revisada y colocó al evento volcánico 20 años antes de AD 536. Sin embargo, recientemente ha habido un esfuerzo conjunto para ubicar todas las muestras de corazones de hielo de Groenlandia en una misma escala temporal, basada en el recuento anual de capas (Vintner et al. 2006). Debido a que todos los corazones de hielo están siendo analizados conjuntamente, las ambigüedades en un corazón pueden ser corregidas cotejando con otros. Una vez que los datos estén bien establecidos, los registros de sulfato (SO4) (que generalmente muestran el impacto de gases volcánicos), pueden ser examinados para ver si éstos coinciden. Y así lo hicieron:
El segundo pico de sulfato de la figura corresponde al año AD 534, que es suficientemente cercano a AD 536, dejando uno o dos años de error en el recuento. Se debe notar que el pico alcanzado en AD 534 es menor que el alcanzado unos años antes. Sin embargo, cuando se evalúa la importancia de una erupción, un pico de concentración de sulfato en Groenlandia no es suficiente, ya que esto podría significar que hubo una erupción en un área cercana. En vez, un pico de sulfato coincidente en la Antártida significa que la erupción ocurrió probablemente en algún lugar en el trópico y que la circulación atmosférica transportó los gases a ambos hemisferios. Es aquí donde intentos previos han fallado. La cronología de las muestras de corazones de hielo antárticos es mucho menos exacta que las de Groenlandia porque la acumulación en la Antártida es más lenta (no se nota tanto). Sin embargo, la relativamente nueva muestra de corazón de hielo llamada Dronning Maud Land (DML) tiene una resolución comparable con las muestras de Groenlandia, y ésta muestra un claro pico de sulfato alrededor del año 542 +/- 17 años. Este resultado es suficiente para coincidir con el pico de sulfato de AD 536 en Groenlandia. La corrección necesaria para que estos eventos estén perfectamente alineados también compensa las aparentes diferencias cronológicas de otros eventos menos importantes en los 100 años subsiguientes.
Probablemente en el año 536 hubo una erupción volcánica en algún lugar en el trópico, de la magnitud de Tambora en 1815. Se ha especulado con que fue una erupción del volcán Krakatoa (anterior a la de 1883), pero esta especulación es incierta, así como las numerosas consecuencias atribuidas a éste evento, como la caída del Imperio Romano o el surgimiento del Islam. Sin entrar en mucho detalle al respecto, esta cita de Michael de Syrian indica, dramáticamente, el potencial que tiene el clima y eventos volcánicos como éste para arruinarle el día a cualquiera:
“El sol estaba oscuro y su oscuridad duró 18 meses; cada día brillaba por cuatro horas, y aún así ésta luz era una sombra débil… los frutos no maduraron y el vino tenía sabor a uva ácida.”
# 147 David — see below. Thanks!
# 149 Hank — thanks.
Hank, also see:
The Lovelock Interview:
http://www.guardian.co.uk/theguardian/2008/mar/01/scienceofclimatechange.climatechange?gusrc=rss&feed=networkfront
And from 1998, ten years earlier, in “Essays on Science and Society,”
Science Essay:
“a book for all seasons.”
http://www.sciencemag.org/cgi/content/full/280/5365/832?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Lovelock+essays+on+science+and+society+&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
# 147, David B.Benson took me rightly to task, read on. . .
David B. Benson,
I just now scanned Archer/Ganopolski’s paper, and am printing it out for leisurely reference and to chase references, etc.
What little I have digested in the last few minutes makes me wonder which plants survive the temperatures that will/would be forthcoming with another 5000 Gt C in the air.
I will read the paper completely but 5 trillion tons C combines with O2 to make 44/12’s times that much CO2, such that we add another 18.3 trillion tons or 18,300 Gt CO2 to the atmosphere. It takes a fire (combustion) to join the C to the O2, and it gives off some chemical reaction heat, which I will ignore for this back of the envelope approach.
. . . .[Come on! Imagine — Air/ fuel explosive! Finely powder 5,000 Gt C spread it as a powder in the appropriate volume of air, throw in a match or spark and . . . locally that is quite an explosion, and changes a lot of carbon dust to CO2. . . Slow burn also produces some BTUs. . . or maybe CH4 . . .( Filmmaker’s, we’ll get back to “The Day The Arctic Burned” (Sensational!-low-budget climate-change-film in the spirit of The Day After Tomorr . . . ). . .methane rises, bubbles to the surface, froths the Arctic Ocean, Shiphand Seaman First Class Jureska Novograd, who’s still trying to quit smoking, stands in the almost chilly arctic summer air on the bow of the Progresso an open Arctic Ocean-crossing ice-breaker-freighter, bound for Portugal, sees ahead where the ocean looks like it has a new layer of ice, but as the freighter gets closer, Jureska sees the white color is the Arctic Ocean boiling bubbling, seething — and light’s his last smoke. . . .and finally quits smoking. . . but the Arctic Ocean’s surface burns and flashes for weeks and months as the methane rises. . . the Arctic Communities are heavily. . .] . . .
======
Back to the Earth-CO2, on the recovery track. . .
5.0 x1012 x 44.01/12.01 = 18,322 billion tons CO2 That’s what 5000 Gt C + 02 weighs as CO2.
The atmosphere weighs 5135.2 trillion tons (NCAR before Bushed)
44.01/28.96 = 1.5197 (how heavy CO2 is WRT “average” air.)
So we take 5,000 billion tons C combined with O2 for 18,322 billion tons CO2, and add it to the current (385ppmv) 3004.53 Gt CO2 in air “now” to yield a total of 21,327 Gt CO2 in air, and what would that do to the Model Temperatures and length of time to remove from the air?
I’ve done this below showing that the extra 5000 Gt C as C02 corresponds to a value of approximately 2,733 ppmv, or 7 times the current concentration of CO2. That is a possibility (my low budget film above) and no matter how long algae that survive a hot ocean take — we lose a lot of land plants.
(I believe Land plants are perhaps more efficiently exposed to CO2 quantities via immersion in air with the available CO2 than plants in the top couple of meters water — and can capture larger quantities of CO2 on land than plants in water. I grant that some mosses do really well, and will check this assertion (My Act of Faith assertion) out, but for the moment. . .)
==========================================
Ice age CO2 x ratio x weight of atmosphere = weight of CO2 in atmosphere.
0.000280 x 1.5197 x 5,135.2 x 1012 = 2,185.11 billion tons CO2 ice age
0.000385 x 1.5197 x 5,135.2 x 1012 = 3,004.53 billion tons CO2 now
0.002733 x 1.5917 x 5,135.2 x 1012 = 21,326.76 billion tons CO2 (5000 Gt C new)
==========================================
My remarks, Off the Cuff. . .since I have not delved into the full set of references and am only “remarking” on the “conservative approach . . .”
Archer and Ganopolski, in their results section, pgs 4, 5, 6, have serious fun and do not stretch the modeling at all. (Now these models have not at microtime scales real accurately reflected the current arctic sea ice situation.) And I therefore question the average 4.7o C positive perturbation for 500 kyr . [-15] (i think it might be over 8o C).
I realize the Delta T for a CO2 doubling giving 3o C is used, but point out that 2733 ppm is a lot more than doubling-and-a-half and corresponds to more than 7 times the current 385 ppm for which we have no easily antecedent proxy for temperature and near current solar constant.
(We ain’t been here before, exactly. . .just do the best we can from the past record to turn it ahead like a mirror, using our rearview mirror to drive this unknown road; yeah we stumble a lot.)
Karen Bice, et al, (Woods Hole) with the hot tub ocean from 91o to 107o F. 33o to 42o C from foraminifera, and proxy CO2 values from 1300 to 2300 ppmv in the 80 — 100 Mya range (before K/T) had solar constants logically in the ~1356 range. (Solar Constant just whipped out here as a linear function from Earth current to 4.5 Gya at ~970 W/m2, then back to 100 Mya.)
Read the paper here:
http://www.whoi.edu/science/GG/people/kbice/Bice_etal_2006.pdf
Or the easy version here: http://www.whoi.edu/mr/pr.do?id=10346
The Archer paper and Bice paper only intersect in my mind in the realm of comparative CO2 ppmv’s and terrestrial temperatures. I have recently counted on the ocean’s solubility and temperature as per solubility as a “place” for the CO2 to go, to save us from the death of land/food plants.
Now, it doesn’t look that good. I don’t think the ocean is going to absorb this excess we have now, let alone what Archer and Ganopolski provide caveat to real disaster — which is only cacti and far north phytoplankton as means of re-capturing the CO2 we’ve exhaled to the air. Karen Bice’s 42o C ocean provides one example of past high temperatures and proxied high ppmvs CO2. Oceans don’t get that warm now, according to NASA, NOAA, and I reference this:
http://www.nasa.gov/centers/ames/png/73302main_sst_globe.png
http://www.cdc.noaa.gov.
`
http://www.nasa.gov/centers/ames/news/releases/2002/02_60AR.html
Also relevant: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171753_2004168321.pdf
(from work of Maura Rabbette)
If the “Day the Arctic Burned” (5000 Gt C) arises as a punctuating step with methane release, the temperatures ought to be scaled up to a Delta T (for CO2) of 7.13x instead of 2x, or 4x. Which is a criticism of Carl Johnson’s simplistic linear approach as well. (Not Archer, et al)
Carl Johnson does not really address the ocean contribution, except obliquely. Why, for example, do the ocean depths stay so cool when it is obvious that the ocean basin basalts should be conducting some of the earth’s geothermal through the ocean basins to warm the oceans. Yet Carl only wants to use the top 3000 feet of continental rock to equilibrate with 390 ppmv CO2 temperatures. (Don’t think about this unless you just can’t help it.)
But it does not look good ahead of us.
David B. Benson, I won’t pick on you for “not reading the thread posts” — or thinking you haven’t — ever again! Also want to thank you for the head’s up for the two papers, and I will look for Jim Hansen’s 1500 year extrapolation.
I really really enjoyed the Archer and Ganopolski paper, think they are conservatives, and will dig through the paper again.
I find that I started out totally downplaying the “sulfate aerosol shield” a few months ago — and still do not like it for all the obvious reasons, the main one being that it will be funded by Big Carbon Inc, and possibly be used to extend the use of Fossil C for everything but lubricants, and transportation. Now I am starting to feel P. Crutzen and others have a piece of our only salvation with the way this planetary emergency is playing out.
Huge “moving/running” plants, like the Trifids (original written) version trained genetically to gorge on CO2 in un-ending quantities to their own extinction might be better. . . we could do the same on fossil carbon, huh?
What plants are going to save all creatures, great and small?
Thanks.
Les Porter (151) — You are welcome. See also my comment #150.
In figuring these out, please take into account that Peak Oil, followed not long thereafter by Peak Oil, will limit the ability to attempt to exploit deep ocean methane (strictly natural gas) hydrates. So it is probably more sensible to calculate with smaller figures than 5000 GtC. Use the Peak Oil+Coal figures plus whatever CO2 equivalent for the methane being expressed from bogs and tundra appears to be a sensible estimate as temperatures rise.
You might also wish to study more about PETM. The Wikipedia page provides a starting point and you can also use the search feature at the top of the Real Climate page.
Minor note: the 280 ppm is end of Ice age, beginning of the warm. You can plug in 0.000188 to get the tons of CO2 airborne in a full fledged Ice Age. I meant to put that in there. It is 1466.29 Gt C.
That is what keeps the planet from a snowball with recent insolation. My Quick and Dirty, taken back to say 700 Mya changes the Solar Constant to ~1305 W/m2, which to me is in equatorial wet fluctuating snowy ball range, but obviously with also the possibility of a band of tropical or equatorial zone oceans — where large areas either side of the equator are fluctuating sea ice. That is a while back, the linear extrapolation is from ~1368 “now” to solar ignition ~960 W/m2 4.5 Gyr back “then” in time.
Sorry if I misled anyone. The table figure should have started off with the 188 ppm value, and the others are back of envelope despite the digits.
The 536 AD event, unlike the K/T just cooled things down a little. Warming can also make it hard for crops to transpire and lots of water will be consumed to keep a plant alive in the heat. To exhaustion, demise, exceeding what it has adapted to.
OT, posted here because the original article is by Gavin, to whom this is relevant. In New Scientist for 22 March, p.11, there is an article “Rising Temperatures bring their own CO2”. Fine, you might think, we all know about this feedback. However, in the contents page, the article is pointed to using the words “Climate sceptics may have a point”, and in the article itself, Fred Pearce begins:
“Climate sceptics are right. Temperature increases do precede rises in atmospheric carbon dioxide – the opposite of what you would expect if changes in CO2 were really driving climate change. That’s the verdict of leading atmospheric modeller Peter Cox, a climate expert at the University of Exeter.”
Pearce does go on to say Cox stresses this does not mean we do not have to worry about GHGs, but quotes him as saying:
“People on both sides want a one-way link, but the historical record shows the causality goes both ways”.
No papers by Cox are cited – the most recent relevant one I can find is “Positive feedback between global warming and atmospheric CO2
concentration inferred from past climate change” by
Marten Scheffer, Victor Brovkin and Peter Cox, published in Geophysical Research Letters in 2006 (I can’t find an exact reference). This paper stresses that the historical work on the Little Ice Age agrees with climate model results.
Is Cox given to saying stupid things for publicity, or is this (as I suspect) a misquotation or out-of-context quote by Pearce? (At the end of the article, Gavin is quoted as saying “We are headed into unknown territory and the only things we have to guide us are physics and our knowledge of the past.”) I intend to complain to NS about this irresponsible rubbish, which we are bound to see cited by denialists for the indefinite future, but it would be useful to know who is at fault.
Lawrence Coleman is a pompous ass! There are as many learned neurons on both sides of the AGW or ACC or whatever you wish to call it argument. The IPCC is political and deserving of immense skepticism.
Admit that you will apologize and quit science if you are wrong and only then will you have shown the humanity to be believed by others just as intelligent as you are.
To believe you alone have wrested sense from chaos is laughable. You invite argument by your impudent denunciation of opposing voices.
You are a fool.
John lagace
Houston
John Lagace, OK, so you are skeptical of the IPCC. Fine. So start with the peer-reviewed scientific literature. The number of published studies is a pretty good metric. The number of studies that support anthropogenic causation of climate change outnumber those that do not by roughly 2 orders of magnitude–a pretty good sign of consensus. But don’t stop there. Look at how often the papers are cited once they are published. Here the consensus for anthropogenic causation is even more stark–nearly every study that questions anthropogenic causation pretty much falls flat. They simply do not point to fruitful new avenues of inquiry–being cited only by refutations or when the authors subsequently “update” the cycle a few years hence. Look into the backgrounds of those publishing the “dissenting” studies–virtually none of them are actual climate scientists. Finally, look at the position statements taken by professinal organizations of scientists. Not one actually dissents from an anthropogenic mechanism for climate change. To make the claim that there are “as many learned neurons” on either side of the question of anthropogenic causation is sheer ignorance–the neurons that claim we aren’t behind the changes have never studied climate change.
Finally, might I suggest that you will get much further on this site of you confine yourself to the details of your opponents’ arguments rather than launching ad homenim attacks.
I’m not sure how much to rely on Keys. Reviewing Keys’ book in British Archaeology, the British archaeologist Ken Dark commented that “much of the apparent evidence presented in the book is highly debatable, based on poor sources or simply incorrect” and that “Nonetheless, both the global scope and the emphasis on the 6th century AD as a time of wide-ranging change are commendable, and the book contains some fascinating and obscure information which will be new to many. However, it fails to demonstrate its central thesis and does not offer a convincing explanation for the many changes discussed.
Somewhere I read of a claim that a meteorite impact in northwestern Australia gave rise to 536 AD and all that.
David, you may be thinking of Plimmer? Odd duck. Google for +536 “dust veil” “cometary dust” — lots of stuff out there.
“… 535 AD Krakatoa exploded, as did Rabaul in 536 AD. The Earth passed through cometary dust in 536 AD. The dusty atmosphere reflected heat and darkness prevailed and, as a result, the climate cooled….”
Hank Roberts (159) — Definitely not Plimmer.