Plimer’s Climatology 104
Climatology vs Plimertology
Acronyms and abbreviations used
|AGW||Anthropogenic global warming|
|CF2Cl2||dichlorofluoromethane or Freon|
|IPCC||Intergovernmental Panel on Climate Change|
|YEC||Young Earth Creationist|
Ignore also what Ian Plimer says about the composition of the sun:
The Sun formed on the collapsed core of a supernova. We might have learned in school that the Sun is composed of hydrogen and helium. Suspicions that the Sun is not that simple have been around for more than 30 years. Isotopes of oxygen, magnesium, xenon and nitrogen in the Sun, solar wind, planets, meteorites, solar flares and the Moon suggest that the Sun consists mostly of the same elements (oxygen, iron, magnesium, calcium, sulphur, nickel and strontium) as ordinary meteorites and the rocky planets. 
As is my custom, I placed the marginal note ‘ITS?’ against this, and not simply because the price of science is eternal skepticism. It has been a long time since I taught astronomy and it was news to me, but it may well have been at least part right, and possibly completely right, though it surprised me as I had not encountered it before. But as it turned out, it was not just basic solar physics which was against Plimer on this point. He was also given a public flogging over it by the astrophysicist Michael Ashley in of all places, that favoured journal of denialism The Australian. Ashley’s is one of the most devastating reviews Heaven and Earth has so far received:
Plimer believes “global warming” occurring on Mars, Triton, Jupiter and Pluto proves human emissions of CO2 don’t affect Earth’s climate. He believes that once CO2 levels reached 200ppmv (about half of today’s value) the CO2 had absorbed almost all the infrared energy it could, and further increases will not have much effect. He believes global warming does not lead to biological stress. He believes volcanoes emit significant quantities of chlorofluorocarbons. He believes the sun formed on the collapsed core of a supernova. All these ideas are so wrong as to be laughable: they do not offer an “alternative scientific perspective”.
Plimer probably didn’t expect an astronomer to review his book. I couldn’t help noticing on page120 an almost word-for-word reproduction of the abstract from a well-known loony paper entitled “The Sun is a plasma diffuser that sorts atoms by mass”. This paper argues that the sun isn’t composed of 98 per cent hydrogen and helium, as astronomers have confirmed through a century of observation and theory, but is instead similar in composition to a meteorite.
It is hard to understate the depth of scientific ignorance that the inclusion of this information demonstrates. It is comparable to a biologist claiming that plants obtain energy from magnetism rather than photosynthesis. 
Or perhaps it is comparable to a geologist claiming that mountains are thumbprints of the Almighty in negative hyperspace. But I have lost count of the number of times I have seen the above passage quoted.
The problem with the meteorite sun, adsorption of photons and God knows what else, is precisely that – the God knows what else. Once we come to a howler, as distinct from a statement over which there can be and is legitimate dispute, there is an understandable disinclination on the part of the discerning reader to accept anything subsequent on trust.
It is now 114 years since the Swedish chemist Svante Arrhenius  suggested that small variations in concentration of the trace gas CO2 in the air could have great effects on the Earth’s heat budget. Yet if one goes by Plimer’s book, no chemist or other scientist had bothered to check the relationship between the CO2 concentration in air and that air’s ability to transmit heat. Plimer’s trump card on this very important point is the allegation above that the relationship is a diminishing, not linear one.
He would have done himself a service by reading A Saturated Gassy Argument (a 2 part series) by Spencer Weart, in collaboration with Raymond T. Pierrehumbert , posted on June 26, 2007 (well before his publication date for Heaven+Earth) at , (part 1) and [4.1] (part 2) . Those two scientists refute the CO2 saturation argument so commonly advanced by deniers, though they in turn have their (at least one, and anonymous) critic, , and there is at least one further critic of that critic’s anonymous critique . I suspect that it was Plimer’s contempt for climatology (not ‘real science’ like his own field of geology) that proved his undoing here. As the proverb has it, pride goes before a fall. To which we might add the corollary ‘after a fall, pride just has to go’.
The ‘Greenhouse Effect’  is a bit of a misnomer. For a start, the atmosphere has trace quantities of the greenhouse gases CO2, CH4, (methane) O3, (ozone) N2O (nitrous oxide) and CF2Cl2 (dichlorofluoromethane or Freon) , and also variable quantities of the big one: water vapour. The layering of the atmosphere  ,  in combination with the presence of these gases gives us the present temperature regime at the surface of the Earth. The atmosphere should be regarded not as one ‘greenhouse’ but as many nested ones; greenhouses within greenhouses. It is an oversimplification to model it as a glass roof.
Because of its higher freezing and boiling points, water is distributed very unevenly in the atmosphere, unlike CO2; likewise its abundance in the column of air over any given patch of the Earth’s surface. As seen in any photograph from a spacecraft, the clouds all appear relatively close to the Earth’s surface. That is because the planet, heated both from its interior by nuclear fission and by absorbed solar radiation from outside, heats in turn the lower layers of the atmosphere in closest contact with it. We live at the bottom of the troposphere; the lowest atmospheric layer, whose temperature varies markedly with altitude. It goes from normal temperatures at the surface to -50 degrees Celsius at an altitude of 10 km, where the troposphere with its clouds and weather ends and the weatherless and largely cloudless stratosphere begins.
Higher than 3 km or so above sea-level, clouds are either made up of ice crystals or droplets of supercooled water. The very highest are polar stratospheric clouds, which form between 15,000 and 25,000 metres altitude, or 50,000–80,000 ft. Thus water, whether in the form of vapour, droplets or tiny ice crystals, does not extend all the way to the top of the atmosphere, which from about 3 km to 100 km above the Earth is too cold for liquid water. Only above 100 km, in the thermosphere, does the air attain temperatures normally associated with water in other than the solid state, at up to 1,000 degrees Celsius. This is due to impacts on air molecules by solar wind and cosmic rays. (Because the air there is so thin, astronauts do not feel air at this temperature as hot, and spacecraft are not set on fire by it.) At that height and very low air density, the total mass of water in the thermosphere is negligible.
Whenever the Earth has a stable temperature, it is because it is emitting as much radiation as it receives from the sun and generates internally. If its heat budget goes out of balance for whatever reason, its temperature will rise or fall until a new equilibrium is reached.
A quantity of radiant energy coming in, at whatever frequency on the electromagnetic spectrum, will be either reflected or absorbed at the Earth’s surface. If absorbed, it will warm up the air, ocean water or any solid surface responsible for the absorption. (The Law of Conservation of Energy says that it cannot just disappear.) If reflected, it may be absorbed by molecules in the air that block its path back to outer space; or else make it through them. Some atmospheric molecules which happen to contain three atoms or more, such as CO2, H2O, and CH4, make more of a barrier than do others. If the heat reflected of the Earth, or emitted by the Earth as a ‘black body’, does not make it past the clouds it will finish up heating the atmosphere or be reflected back downwards again.
As Weart puts it:
What happens to infrared radiation emitted by the Earth’s surface? As it moves up layer by layer through the atmosphere, some is stopped in each layer. To be specific: a molecule of carbon dioxide, water vapor or some other greenhouse gas absorbs a bit of energy from the radiation. The molecule may radiate the energy back out again in a random direction. Or it may transfer the energy into velocity in collisions with other air molecules, so that the layer of air where it sits gets warmer. The layer of air radiates some of the energy it has absorbed back toward the ground, and some upwards to higher layers. As you go higher, the atmosphere gets thinner and colder. Eventually the energy reaches a layer so thin that radiation can escape into space.
What happens if we add more carbon dioxide? In the layers so high and thin that much of the heat radiation from lower down slips through, adding more greenhouse gas molecules means the layer will absorb more of the rays. So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get hot enough to radiate as much energy back out as the planet is receiving.
Any [CO2] saturation at lower levels would not change this, since it is the layers from which radiation does escape that determine the planet’s heat balance.
But wait. There’s more.
Atmospheric CO2 traps heat, causing increased evaporation of surface water. Water vapour is a powerful greenhouse gas, and once it condenses into clouds it becomes a remarkable two-way screen for all wavelengths in the visible spectrum and many to either side of it. This is the reason that clouds viewed from the side the sun is shining on (eg from space) appear white, while from below they appear grey to black; and why they can be tracked by radar using reflected microwaves. But their inability to stop all wavelengths is why one can get burnt by the penetrating ultraviolet rays of the sun, even on a cloudy day.
But that is not all, for in this world one thing commonly leads to another. According to Dan Gaffney of the UNSW Faculty of Science:
Water vapour released into the atmosphere adds one degree Celsius to global warming for every one contributed by humanity through greenhouse gas emissions.
The evidence for this phenomenon, long-debated among climate scientists, is now indisputable, according to a review of the evidence published in the latest issue of Science by Andrew Dessler of Texas A&M University and Steven Sherwood of the University of New South Wales.
Known to science as water vapour feedback, it is responsible for a significant portion of the warming predicted to occur over the next century, according to Dessler and Sherwood. This is because water vapour itself is a greenhouse gas.
So buy one degree (with CO2), and get another for free (with water vapour). This is a bonus offer none of us can refuse, because we are in no position to. Thus, to get to the six degree maximum, we need only three degrees worth of CO2. H2O alone will take us the rest of the way. Moreover, that is three degrees Kelvin, because the equations governing absorption and emission of heat demand absolute temperature values. To move from 10 degrees C to 11 degrees C requires on the innocent face of it a whopping 10% increase in absorbed heat; except it doesn’t, because it is the Kelvin temperature that embodies absorbed heat. To move from 283 to 293 K requires only a 293/283 ratio of final to initial heat content, or a mere 3.5% increase. To go from 17 C to 22 C is to go from 290 K to 295 K; a rise in heat content of only 1.7%.
Accordingly, a two degree rise due to CO2 will produce a further two degree rise due to water vapour, making four degrees in all. The next domino to fall in this situation is the methane, locked up in arctic permafrost in Siberia and Northern Canada, and below the deep ocean floors as methane hydrates. In all those locations, it has built up from slow bacterial decomposition of organic matter. Methane is 45 times as powerful a GHG as CO2, to which it oxidizes in about a year after release to the air. The warming produced by this gas may in turn release the final nightmare gas, hydrogen sulfide. Plimer does not mention these potentially disastrous knock-on effects of methane and hydrogen sulfide. More on them below.
If the reader does not wish to buy a copy of Heaven+Earth , then the talk given by the author at the Sydney Mining Club on November 6th, 2008
 covers most of its basic ground.
According to Plimer’s Slide 3, (reproduced on p 242 of Heaven+Earth) average global temperature over the last 600 million years has varied between 0 and 22 degrees Celsius (C). However, that graph is unsourced and appears to be identical to the one published at http://www.scotese.com/climate.htm . That one shows the global mean variation as being between 10 and 22 degrees C or 285-295 degrees Kelvin (K)  . I assume there has been some mistake on Plimer’s part here; such things happen. The scotese global range is 17 +/- 5 degrees C, or 290 +/- 5 degrees K. As the Kelvin scale reflects absolute heat content, that is a variation of a mere +/- 1.7% in the latter across the whole geological record in time; to my mind an incredibly narrow range. James Lovelock cites this in support of his argument that the Earth as an integrated whole constitutes a thermally self-regulating living organism; a superorganism like an ant colony, but on a far vaster scale. Aside from that, it appears that an Earth without polar icecaps would warm to a point of equilibrium where the cloud layer stopped both sufficient heat coming in from above (ie from the Sun) and escaping from below to hold that equilibrium. Hence the planet’s record of relative temperature stability.
Atmospheric CO2 has varied far more than average temperature, which latter has plateaued for long periods at the maximum of 22 degrees C or 295 K, and held that mean of 17 +/- 5 degrees C, or 290 +/- 5 degrees K. This suggests that there is working within the Earth’s climate system a negative feedback mechanism akin to the thermostat of a refrigerator. I would suggest a major role in that is being played by water vapour. Once the icecaps are gone, along with their thermal inertia and high albedos, the temperature of the oceans rises to the point where atmospheric water vapour and cloud cover block enough incoming radiation from the sun to establish a new equilibrium between incoming and outgoing radiation. Based on the geological record, we can say with high confidence that a warming phase will not exceed a maximum average surface temperature somewhere between 10 C and 22 C, with a global geohistoric mean of 17 C. Only if circumstances are very extraordinary, as at the end-Permian, will it go higher. [14.1] But all the ingredients are there for a repeat of such an event, and rapid global warming raises its probability too far above zero for comfort or complacency. But complacency is what Plimer and the rest of the denialists are urging.
The temperature record back beyond the use of the first thermometers has to be based on study of proxies like tree rings, calcareous shells and radioisotopes.  In Plimer’s slide, reproduced on p 242 of Heaven+Earth, there is shown a massive drawdown of atmospheric CO2 over about 130 million years from the mid-Devonian to the end-Permian, and a correspondingly massive temperature drop from the top of the range to the bottom of it across the same period of time, with closely associated relatively rapid CO2 and temperature rises at the end-Permian.
The following table gives Plimer’s cycles involving the Earth:
|143 million year||Galactic|
The orbital cycles probably influence glaciations, but only in the context of the non-cyclical arrangements of continents, oceans and mountain ranges. There is no easy correlation with any of the above with the longer term geological temperature record since the Cambrian.
It would be interesting to have photographs showing panoramic (mountain-top) or satellite views of the Earth’s surface taken at times of temperature maximum, say in the Cambrian or (most of) the Mesozoic. Besides vastly different arrangements of the continental land masses, I would guess that there would have been far fewer sunny, cloudless days and far more in the way of overcast to leaden skies, punctuated frequently by tropical-style storms, even up to high presently temperate latitudes.
To a large extent, our present global climate appears to be the product of the two icecaps at the rotational poles of the Earth in combination with the fact that much of the continental mass lies oriented in a north-south direction between them. There is more or less continuous land from the Arctic Ocean to the Cape of Good Hope at the southern tip of Africa, at latitude 34 degrees south (at about that of Sydney). Similarly one could walk from the frozen top of Canada to Cape Horn, at the southern tip of South America, save for the odd river and the Panama Canal. However, had the continents moved differently over the Earth’s mantle while retaining their same relative positions to each other, one pole could have finished up centred on Borneo, and the other on Northern Brazil. The equator of this Earth would have followed the line of the Greenwich Meridian, passing not only through Greenwich, UK, but the Atlantic ‘west’ (presently south) of Ghana and continuing on a course taking it over ore round Antarctica and from there right across the Pacific to the present North Pole, roughly via the Bering Strait. This can be seen by taking an ordinary globe and turning it roughly horizontal. The Borneo-Brazil rotational axis could still be at the same angle to the plane of its orbit round the Sun (23 degrees), retaining the seasons.
One could sail right round the equator of such a world, hardly ever deviating from it, and then by only about 15 degrees of present longitude. One would deviate only to avoid West Africa and Antarctica. My guess is that the wind patterns on such a globe would have been based not on a lot of little gyres, as at present, but on one huge equatorial air stream, comparable to the equatorial winds of Saturn. Perhaps also the Coriolus force would have produced a train of gyres within it; a line of vortices from whirlwinds up to hurricanes marching in file like mediaeval monks right around the globe. Their course would not have been impeded by any mountains save the Pyrenees, which could be skirted by a minor deviation off the ‘equator’ into the tropical ‘east’ Atlantic.
Mariners have come to know the delights of the Roaring Forties, the Howling Fifites and Screaming Sixties that must be crossed along every line of access to Antarctica, because at those latitudes there is ocean right around the Earth, and the winds to not encounter any barrier mountain ranges. But I digress.
To Plimer, it is inconceivable that we humans could do anything through our economic activities to alter the Earth’s climate, even though in the next breath he says that AGW would be a good thing. To me and many others since Arrhenius, it is quite conceivable, and may well be happening, and promises to be not very good at all.
The problem: if we did not live in such a cold phase of the Earth’s climate history, or in such a mountainous phase of its tectonic history, things perhaps would not be so liable to turn desperate. If ours was a Jurassic world sans dinosaurs, skiers would have their problems, but warming would probably not pose the same danger that it now does. To put it bluntly, in the next century or so on present trends we face the gradual loss of every coastal plain and port city in the world – a creeping New Orleans disaster or Asian tsunami – due just to rising seawater and storm surges. Those are places where much of the world’s population lives and its agriculture takes place. This is the world we have built and know, so to a considerable extent we are now both obliged to reduce the risk of AGW and to work against ‘nature’. That has been what the Dutch have done for centuries, ever since they began building the dyke systems to hold back the North Sea.
The alternative to reining in aerial carbon is not to just go with the flow of nature and let things turn out as they may, because in this ice-capped world a slow buildup of methane has taken place in the arctic permafrost, and the even worse combination of methane and hydrogen sulfide in the anoxic conditions of the sediments below the ocean floors. Both of these are potent greenhouse gases in their own right. Moreover, methane reacts readily with ozone, and could strip much of the ozone out of the atmosphere, exposing life everywhere to enhanced solar ultraviolet, which clouds to not block. Finally, hydrogen sulfide is as poisonous as any gas gets. Rapid climate change threatens a grand finale in which these gases come bubbling out of the sea floor in huge self-amplifying volumes. There is considerable evidence that this is precisely what happened in the end-Permian extinction event, which probably took at least 10,000 years to play out. [15.1] It was the greatest crisis ever in the history of life, wiping out according to some calculations 95% of all species. [15.2] Of this, more below.
Continents may rise and fall separately, but the oceans do not, because they are all one. Global warming and potential sea level rises up to 70 metres promise gradual creeping disaster on the shores of all of them.
To sum up: the Earth’s presently rising sea levels can only be due to two possible causes. Either the Earth is capturing and retaining an increased amount of heat from the sun, or more heat is coming up from its interior. In the latter case, one would reasonably expect the released heat to be associated with increased volcanism and earthquakes. But we have been in a quiet phase for those for about the last 20 years. Increased capture and retention of solar radiation would be due possibly to the sun becoming more radiant, or to the Earth becoming more radiation absorbent. It would appear that the periodicity of the glacial advances and retreats, commonly known as ‘ice ages’ can be linked in part to variations in solar intensity, otherwise known as solar flux, brought about by internal cyles within the Sun itself and variations in the Earth’s orbit. (See in this connection Heaven+Earth p 234 and slide 2 at .) We are in the middle of a warm phase of the glacial cycle that established at the start of the Pleistocene, about 2.8 m years ago, so the Earth should be more likely cooling, not warming.
Apart from the known cycles we have more chaotic processes on Earth such as volcanism, sea floor separation and continental drift. The latter has resulted in the last 3 million years  in the closure of the isthmus of Panama, resulting in the near-complete walling off of the Atlantic from the Pacific by the joined American continents, with the Circumpolar Current in the Southern Ocean and the Roaring Forties, the Furious Fifties and the Screaming Sixties, (as named by the sailors who first ventured there) thermally isolating Antarctica .  Though the geological record indicates that the South Geographic Pole has always lain under a continental mass and the North Pole never so, the continental arrangements that have arisen in the recent past have resulted in the near-complete enclosure of the Arctic Ocean by land, making the retention of Arctic sea ice and thus the bulk of the northern icecap possible. This two-icecap Earth is exceptional. In the Late Carboniferous glaciation, there was only one icecap.  The Earth has had an ‘ice-house’ climate for the last 30 million years  is now in a warm phase in a cycle of glacial advance and retreat,  has been for the last 2.58 million years,  and will be for perhaps millions of years more into the future.
In approximately 4.6 billion years of Earth history, there have been three major episodes of glaciation. The Varangian glaciation occurred during the Proterozoic part of the Precambrian period about 700 million years ago (m.y.a.). The next one happened in the late Paleozoic Era around 300 m.y.a. The most recent period of glaciation started approximately 1.6 m.y.a. and ended about 10,000 years ago.
In 2008, a somewhat naïve and enthusiastic Englishman almost perished trying to paddle a kayak to the North Pole to highlight the effects of human induced global warming. He could only paddle to 960 km from the Pole. In 1893, Nansen was able to kayak to 800 km from the North Pole. The pathetic Pythonesque paddle in 2008 was to prove global warming had reduced the extent of sea ice. It demonstated the exact opposite…
… Extreme caution must be exercised using sea ice conditions as an indicator of climate trends and many local conditions change the extent and thickness of sea ice.
Even more extreme caution must be taken when computer simulations claim that there is human-induced global warming at the poles. We are a long way from understanding natural variability. 
Plimer is correct in the last sentence there. However the satellite data are against him on the rest of it; both with their altimetry and their direct photography.
From my submission to the 2009 Australian Senate Inquiry on carbon abatement:
In Asia and Alaska, using satellite images and aerial photographic comparison over long time spans, there have been extensive glacier terminus surveys illustrating long term retreat involving no less than 95% of the glaciers. In 2005 there were 442 glaciers examined, of which only 26 were advancing, 18 were stationary and 398 were in retreat: that is, 90% of them retreating. In 2005, for the first time ever, no observed Swiss glaciers advanced. And of the world’s 26 advancing glaciers, 15 were in New Zealand.
According to a report in the Melbourne Age of 6.4.2009, “up to one-third of all Antarctic sea ice is likely to melt by the end of the century, seriously contributing to dangerous sea level rises, updated scientific modelling on global warming shows… The modelling is the first release of a landmark study being conducted by the global scientific body the Scientific Committee on Antarctic Research, made up of the peak scientific bodies from 23 countries including Australia.”
Though air temperatures whether local or worldwide, daily or annual average, may for various reasons not reflect it, the world is none the less clearly warming. It is now possible to fulfill Lord Franklin’s dream and sail the Northwest Passage over the top of Canada from the Atlantic to the Pacific, at least for one month or so in the Northern summer. Possibly within the next ten years ships will be able drop anchor in an essentially ice-free Arctic Ocean, right at the North Pole. That together with the satellite altimetry data on sea levels, testifies to the rapidity of global warming, and of the onset of the positive feedback loops that can only further accelerate it. The safest assumption we can make, in short, is that we face a planetary climate emergency, requiring urgent economic reforms on a comparable scale to those which took place in Australia after the declaration of war in 1939. [24.1]
See also Sea Ice Yearly Minimum with Graph Overlay 1979-2008 
Ships are now regularly sailing the Northwest Passage in modern arctic summers. We might say they sail downhill on the graph of the 29 years of sea ice yearly minimum 1979-2008 seen in the above link. But I am sure Lord Franklin, whose expedition ships Erebus and Terror were last sighted moored to an iceberg on June 25, 1845, would be of two minds over this news. 
As floating ice cubes melt in a glass of iced water, the liquid water does not change level. That is primary school physics. The albedo of the Earth is the ratio of the radiant energy reflected by the Earth to that received by it. As the area of sea or land covered by highly reflective ice and snow contracts, the albedo falls. Dark ocean exposed by the ice cover lost absorbs more radiant energy than it reflects. The Arctic Ocean (and thus the Earth) becomes slightly less reflective than it was the year before, and so slightly warmer. But ice is also a poor conductor of heat, so the next winter’s ice helps the ocean retain the heat gained the previous summer. And so the temperature of the ocean ratchets slowly up in a positive feedback loop.
So in addition to the tipping points in nature already mentioned, there is another: 0 degrees Celsius, which is 32 degrees Fahrenheit, which is 273.3 degrees Kelvin. If we warm a cold ice crystal up from somewhere below zero Celsius, it will stop warming when it reaches zero Celsius and start changing state. All the heat it absorbs no longer serves to change its temperature, but to overcome intermolecular forces instead. It crystal structure progressively collapses as one intermolecular bond after another reaches its own tipping point and releases. The albedo of an icecap changes because of existence of all those molecules reaching their own individual but identical tipping points.
Warming of northern Canada and Siberia has the potential to melt the permafrost and bring large masses of methane, a greenhouse gas 45 times more potent than CO2, out of the ground and into the air, warming the planet still further. Heat passed to the oceans may trigger the release of more methane from vast masses of methane hydrates buried below the ocean floors. Such a ‘methane belch’ may well have been involved in the Permo-Triassic crisis we have already considered:
The possible causes which are supported by strong evidence… appear to describe a sequence of catastrophes, each one worse than the previous: the [volcanic – IM] Siberian Traps eruptions were bad enough in their own right, but because they occurred near coal beds and the continental shelf, they also triggered very large releases of carbon dioxide and methane. The resultant global warming may have caused perhaps the most severe anoxic [loss of dissolved oxygen – IM] event in the oceans’ history: according to this theory, the oceans became so anoxic that anaerobic sulfur-reducing organisms dominated the chemistry of the oceans and caused massive emissions of toxic hydrogen sulfide. 
Hydrogen sulfide is also known as ‘rotten egg gas’, and is just as toxic as the gases carbon monoxide and hydrogen cyanide. At 10 ppmv adverse physiological effects start, and lethal concentration is reached at 200 ppmv, which is about half the present atmospheric concentration of CO2. It is also impossible to smell at such high concentration, due to the deadening effect of the gas on the olfactory sense.
A sequence of catastrophes such as described above is the sort of scenario envisaged by climate ‘alarmists’ as a future possibility. CO2 is bad enough, but despite favourable prognoses based on ‘saturation’, it is amplified twofold by water vapour feedback, and the total increase in the heat contents of atmosphere and oceans can in turn trigger off a self-amplifying methane belch, leading to such warming of the oceans that we eventually get into self-amplifying anoxia and even local poisoning by hydrogen sulfide released by presently-buried anaerobic bacteria. There is strong but not conclusive evidence that it happened 251 million years ago in the already mentioned Permian-Triassic extinction event.  Estimates of recovery time vary from 4 million years to 30 million years, ie in the late Triassic. , 
Hydrogen sulfide belches, particularly in confined spaces  have caused deaths in modern times, and may be implicated in past mass-extinction events associated with atmospheric CO2 spikes.  and  H2S coming out of swamps and river estuaries has resulted in local atmospheric concentrations sufficient to cause deaths, particularly in confined spaces, and may have been involved in one of the most baffling mysteries in Australian forensic pathology. 
Readers living in Sydney, which is built on top of about a 5 km thickness of Permian and Triassic sediments, can see evidence of the Permian-Triassic catastrophe at first hand. A trip to the Scenic Railway  at Katoomba, 103 km from Sydney, is well worth the time. One rides in an open carriage on the steepest incline railway in the world down through a vertical 178 metres (587 ft) of Middle-Triassic sandstones (aged 225-230 M years.) 
(The link by the way is to an article by creationist geologist Andrew A. Snelling, B.Sc. (Hons), Ph.D, who holds degrees from UNSW and Sydney University respectively. Ian Plimer should note that Noah’s Ark could well turn up in Katoomba .)
These, like all Triassic deposits, have very little in the way of fossils or coal involved in them. Considering what came before, that is understandable. It is interesting that the geological formations dating from the time when life was going through its greatest crisis should be construed by a geology PhD, who just happens to be also fundamentalist young-Earth creationist, as evidence for the biggest catastrophe described in the Bible, namely Noah’s Flood. Plimer with strong evidence dates that Biblical event to the time of the flooding of the Black Sea basin by the inrushing waters of the Mediterranean 14,500 -12,900 years ago, [37.1] on which he is almost certainly right. Young-Earth creationists would date this event, along with all other sedimentary strata, at some time after October 23, 4004 BC.  
On reaching the bottom station of the Scenic Railway, one alights onto the Permian strata that include the coal measures underlying most of the Sydney Basin, making it one of the largest sources of high grade coking coal in the world. A short walk from the bottom station leads to places where the Permian-Triassic boundary can literally be examined firsthand. This of course is by no means the only place on Earth where it can be seen.
A major qualitative change in the sedimentary rock strata is clearly visible. The shales, mudstones, siltstone and coal deposits of the Permian are overlain with coarser-grained sandstone beds in the main, these being of the deepest and earliest (Narrabeen sequence) Triassic deposits. The stratigraphy from the Permian  to the Triassic  here is of shallow marine origin and continuous: there being no geological discontinuity that would indicate say that the area began as the bottom of a sea, was later uplifted and then later still subsided, after which further deposition occurred. These rock layers tell a simple, straightforward story. At this location in the Permian, there was abundant plant life. In the Triassic there was not; but there was huge weathering of rocks taking place, erosion of the sediments, and their deposition in marine environments above the contemporary continental plate. The Sydney Basin is huge,  ; 
The Scenic Railway  began in the late 19th C as the means of transporting Permian coal from the mines in the Jamison Valley below Katoomba to supply the furnaces of the power station at Katoomba and also household and business fires.  .
The apparent late Permian marine regression is attributed to water withdrawing into a deepening ocean basin. The basaltic ocean bottom continued to sink during an unusually long period of cooling (and decreased buoyancy) of laterally spreading ocean ridges during a time of increased linking together of plates, and corresponding decreased rate of sea-floor spreading.
The oceans, in other words, became deeper and narrower, decreasing the area covered by shallow-water environments (modern examples: the floors of Bass Strait and of the English Channel) as water drained into the deep ocean basins, space having been made available by sinking of the ocean floors.
If a given sea-floor spread in one area is not matched by a compensating contraction in another, then overall increase in crustal area must have occurred. The planet may have inflated slightly, like a basketball as it is being pumped up. Such, if it occurred would probably be due to internal heating, or to gas coming out of magmatic solution somewhere below the ocean floor, consistent with the known and extensive Siberian Traps volcanism of the late Permian,  which could have set off the chain of events leading to disaster as CO2 released into the atmosphere led in turn to releases of vast quantities of methane: one tipping point after another being crossed. It was certainly the biggest of the ‘Big Five’ extinction events  as we find them across the full extent of geological time.  . It “killed 53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species (including plants, insects, and vertebrate animals). 57% of all families and 83% of all genera went extinct. “
It happened 251 million years ago.
In the Pleistocene, the Earth got to be within a degree or two of as cold as it has ever been since the Cambrian.  It was near the lowest end of its 10-25 degrees C range of mean temperature. Only there, and near the Ordovician-Silurian and Carboniferous-Permian boundaries has it been so cold. It is perhaps such conditions, coupled with rapid deposition of silt or fine ash on the sea and ocean floors, which enables the rapid burial of plant and animal remains into anoxic conditions, leading to steady buildup of methane and hydrogen sulfide in those sediments. In the modern world, agriculture on all continents has led to practically every river becoming a flow to the sea of diluted mud. There is no shortage of fine sediment to bury organic remains in anoxic conditions.
There is already considerable H2S and methane under the sea floors. We are arguably adding to it at a relatively rapid rate, and are thus helping to set up one of the necessary preconditions for another Permian-Triassic type disaster, which also happened in a period of warming after glaciation. I would emphasise however that more than just sequestration of H2S and methane is needed for a repeat of the Permian-Triassic event.
From the start of the Permian (at -299 million years ago) to its end (at -251 million years ago), the Earth went from about as cold as it has ever been to the very hottest, in the extinction event itself at -251, It also fell victim to coincidence: the eruption of the Siberian Traps. These were huge basaltic flow volcanoes which ejected likewise huge quantities of dust and sulfur dioxide into the air, covering an area larger than Western Europe with basalt and ash layers many hundreds of metres thick. 
I don’t want to alarm you, but something similar may be what is lurking right now beneath Yellowstone National Park in the US and Koba in Sumatra, Indonesia.
To that extent, we are driving close to the edge of a mountain road, where tipping over the edge could put us into another Permian-Triassic event. Our bus is to some extent steerable, though the brakes are a bit dodgy. The road has a loose surface, no safety rail, and the odd steep run downhill ending in a hard bend. Deep in the valleys below these bends are piles of rusting wreckage of buses that have not made it: analogues of the geological record.
TO Plimer’s Climatology 105: Lord Franklin’s Dream turned nightmare >>>
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TO Plimer’s Climatology 106: His Lordship’s List >>>
NOTES AND LINKS:
 Plimer, Heaven+Earth pp 115-116
[14.1] (Heaven+Earth 242)
[15.1] Lynas, Mark, Six Degrees, HarperPerennial, London 2008 pp 234 – 238.
[15.2] Lynas 2008, p 234
 http://www.sydneyminingclub.org/presentations/2008/november/plimer/player.html .  http://en.wikipedia.org/wiki/Isthmus_of_Panama in the closure of the isthmus of http://220.127.116.11/search?q=cache:V20G2Xf_5_UJ:www.antarcticanz.govt.nz/downloads/information/infosheets/connections.pdf%3FPHPSESSID%3D82900578bc9f9fb6267a2c6b47ab6dc+thermal+isolation+of+antarctica&cd=1&hl=en&ct=clnk&gl=au
 Heaven+Earth pp 290-1
[37.1] Plimer Heaven+Earth p 41
 Lynas, Mark, Six Degrees, Harper Perennial, London. 2007 p 230