GEOLUTION: HIGHLIGHTS IN THE HISTORY OF THE RELATIONSHIPS BETWEEN PHOTOSYNTHESIZERS AND THE EARTH'S CLIMATE.
This work is a collection of quotes highlighting the critical role of Photosynthesizers in determining the Earth's climate for the last four billion years. The intention of this work is not to sketch the structure of a scientific treatise on 'Photosynthesizers and the Climate' but to draw two political conclusions about the current environmental crisis: that Reforestation is vital for combating global burning and that Forests are essential for stabilizing the climate. Over the last decade or so, greens have systemmatically ignored these issues. As far as they are concerned Forests don't exist, Forests have no influence on the climate - only Carbon emissions have an impact on the level of atmospheric Carbon. Nelson covered up one eye as a prelude to glorious deeds; greens do so in order to remain irrelevant.
i) Overview.
I: The Main Photosynthesizers in the Earth's History.
"At the beginning, 3.8 or 3.5 Ga ago, only anaerobic autotrophs capable of tolerating high temperatures thinned out the atmospheric CO2, through carbon fixation. Fossil organic carbon was utilized by anaerobic heterotrophs to reinforce the effectiveness of the late Archean greenhouse. With the increasing solar luminosity during early Proterozoic time, new life forms such as cyanobacteria evolved, removing CO2 from the atmosphere and storing it in stromatolitic carbonates. Over-eager cyanobacteria may have consumed too much greenhouse CO2 to cause glaciation. Their decline coincided in timing with the rise of the Ediacaran faunas which had no carbonate skeletons. The change in the mode of carbon-cycling may have started the warming trend after the Proterozoic glaciation. The Cambrian explosion was an event when skeletal eukaryotes usurped the function of prokaryotes in removing greenhouse CO2 through CaCO3 precipitation. With the evolution of land plants, coal-makers took over the 'air conditioning' duty. They over-did it, and Permo-Carboniferous glaciation ensued. After a wholesale turnover of the faunas and floras at the end of the Palaeozic, more CO2 was released than fixed in early Mesozoic time. The warming trend reached its zenith in the early Cretaceous, when flowering trees and calcareous plankton began to flourish. The decline since then, with a temporary restoration during early Palaeogene time, could be a manifestation of the varying efficiency of extracting and burying carbon dioxide in the form of inorganic and organic carbon."
II: The Main Ice Ages.
"Hambrey has compiled a chronology of glaciations. It shows a glacial phase between 2500 and 2000 million years ago, a period more or less free of ice for 1000 million years after that, followed by frequent peaks of glaciation during the past 1000 million years. Of these peaks, the two with the most secure claim to be called worldwide glaciations - 'true' ice ages - occurred between 700 and 600 million years ago, and between 250 and 230 million years ago."2
ii) The Hadean (4.6-3.7 bya).
Lovelock and margulis have named the earliest part of the Earth's history as the hadean period, 4.6-3.5 billion years ago (bya) which was then followed by the Archean 3.5-2.5 bya. Most geologists regard the archean period as covering everything prior to 2.5 bya. The proterozoic period stretched from 2500-520 mya; whilst the phanerozoic has existed from 520 mya to the present.3 Lovelock claims the Earth's climate was not stable during the hadean period. When the Earth was first formed there were high levels of radioactivity and its surface was a fairly tempestuous place where meteorite showers met volcanic eruptions.
iii) The Archean (3.7-2.5 bya).
Climate.
Lovelock believes the archean period marks the first appearance of life on Earth and thus the Earth's life, "The Archean saw early bacterial life forms and the birth of Gaia."4 However, it could be argued that climate didn't materialize until Photosynthesis began. It has been suggested that .. "the surface temperature on Earth may have been 70C at about 3.0 Ga and 52C at 1.3 Ga."5
Photosynthesizers (Anaerobic Autotrophs, Bacteria, Stromatolitic Carbonates).
It has been argued the first Photosynthesizers came into existence very early in the Earth's history, "Some of the oldest rocks on Earth (were) laid down 3.8 billion years ago. Some chemical analyses suggest there is a 12C surplus in these rocks, and if this is true life must have put it there. As evidence of Photosynthesis it would be startling because it comes a mere 200 my at most after the Earth grew cool enough to live on."6 The dominant Photosynthesizers during this period were anoxic (anaerobic) bacteria (prokaryotes) which lived in the oceans. The most well known of which was Cyanobacteria. "Stromatolites .. turned out to be the work of bacterial communities dominated by Photosynthesizing cyanobacteria, which form felt like microbial mats covering the surface of shallow water sediments. The microbes secrete a tacky gel that protects them from ultra-violet radiation and environmental contaminants. But the gel also causes sediment to stick to the microbes, and when the ensnared sediment grows so thick that it dims the light, the community creeps sunward and a new microbial mat starts to build, and then another, and so on. Stromatolites are trace fossils, byproducts of life."7 "At the beginning, 3.8 or 3.5 Ga ago, only anaerobic autotrophs capable of tolerating high temperatures thinned out the atmospheric CO2, through Carbon fixation. Fossil organic carbon was utilized by anaerobic heterotrophs to reinforce the effectiveness of the late Archean greenhouse."8; "Another major sink for Carbon was the stromatolitic carbonates. Stromatolites are known from archaean times. Microbes forming stromatolites could be anaerobic, or aerobic, autotroph or heterotroph, phototroph or chemotroph.9; .. "the community of bacteria collaborated in constructing mats - and most of life's history has been conducted inside these mats. Sealed in slime from the cruelty of ultraviolet radiation, mats formed mounds, and columns, and pillows, and fingers; mats formed great cones in the deeper sea, the like of which have not been seen on Earth for 1,500 million years. Ultimately, mats maketh man."10; .. "cyanobacteria were very effective in consuming CO2 to make limestones: they are good air conditioners for Gaia."
In
their Photosynthetic process Cyanobacteria derived hydrogen from hydrogen sulphide.
It was only later that bacteria, and eventually green Plants, emerged which
obtained hydrogen from water, "The first organisms to exploit it (Photosynthesis)
were bacteria which obtain their hydrogen mainly from hydrogen sulphide (H2S)
or organic acids, and their Carbon and oxygen from Carbon dioxide. The bacteria
lived in water (as their descendants do to this day), and obtained the raw materials
for Photosynthesis from the water. Bacterial Photosynthesis was followed by
another version of the process, using a different kind of chlorophyll, and it
was this type of Photosynthesis that led to the evolution of green Plants. The
essential difference is that in Plant Photosynthesis the hydrogen is obtained,
not from hydrogen sulphide, but from the photolysis (breakdown using light energy)
of water."
The release of oxygen into the atmosphere by Photosynthesizers posed a number of threats. It threatened to kill Bacteria which could not tolerate such a poisonous element as oxygen. It changed the chemical composition of the atmosphere by replacing Carbon. And it posed a threat to the greenhouse effect, "The growth of Photosynthesizers would have reduced the atmospheric abundance of this gas (CO2) and consequently the protective warmth of the gaseous greenhouse."13
Oxygen.
"When volcanic upsurges brought raw iron and other unoxidized minerals or gases to the surface, these would react chemically to pull free oxygen out of the environment."14
Carbon Emitters (Methano-bacteria).
The Photosynthetic absorption of Carbon was balanced by the release of Carbon by methano-bacteria, "If the archean microbes were the same kind as those of today, their thermostat would have been set too low to prevent the Earth from freezing at the time of reduced solar luminosity there must have been another regulating mechanism."15
iv) The Proterozoic (2.5 bya-700 mya).
I: Early Proterozoic.
The Continued Dominance of Cyanobacteria.
The early part of the proterozoic period continued to be dominated by Cyanobacteria.The Rise of Eukaryotic Life Forms.
"For more than 1.5 billion years after the first bacteria appeared in the Earth's primeval seas, prokarotes had a monopoly on Planetary life. With the emergence of eukaryotes, that quickly changed."16; .. "the eukaryotic take-off about 1 billion years ago .. "17 The first types of eukaryotic life forms were Protista .. "a burst of evolution that gave rise to groups that include red and brown algae, chromophytes (such as diatoms and yellow-brown algae), green algae, fungi, and animals. Estimates based on the "molecular countback" system suggest that this surge took place 1 billion years ago, and the fossil record seems to confirm this."18
Photosynthesizers (The Rise of Eukaryotic Photosynthesizers [Protoctists/Algae]).
It wasn't until the proterozoic that eukaryotic life-forms and eukaryotic Photosynthesizers appeared. The first eukaryotic life forms on Earth were the Protoctists, "This development, heralding the possibility of multicellular life, may have been the single most significant evolutionary leap since the origin of life."19 The first eukaryotic Photosynthesizer was Algae .. "green photosynthesizing microbes called cyanobacteria .. resisted digestion inside larger living cells and continued to photosynthesize. From partly digested cyanobacterium and a hungry translucent swimmer, a new individual, the alga, evolved."20;"Earliest life forms of prokaryotes, bacteria, cyanobacteria, etc, characterized by cells that lack membrane bound nuclei and similar organelles. Some time after 1.5 Ga, during late Proterozoic time, the eukaryotes appeared. These are unicellular or multicellular organisms, such as protists, fungi, plants and animals ... "21; "The necessarily aerobic microbes originated, however, only about 2.0 Ga ago, and first became abundant and globally widespread between 1.7 and 1.5 Ga."22
Climate.
First Ice Age: "We cannot draw a map of the world as it was more than 2000 million years ago, but there is some reason for supposing that large land areas were located in high latitudes. There is evidence that parts of what are now north america, south africa and australia were covered by ice sheets about 2300 million years ago."23; .. "It shows a glacial phase between 2500 and 2000 million years ago .."24
Climate and Photosynthesizers.
Hsu believes the emergence of eukaryotic Photosynthesizers may have had a significant impact on the climate, "The rise of eukaryotes coincided with the decline of the stromatolitic communities. Is that an evidence of Gaia's endothermic forces at work?"25; "Cyanobacteria could thrive and get a big share of gaia's Carbon budget when it was very hot; they could thus have worked effectively as a conditioner. When the temperature became moderate, or cold, the metazoans, with their more advanced organization, had a chance to take a bigger share of the Carbon pie."26
The Release of Oxygen into the Atmosphere.
"Prokaryotic microbes (formerly known as blue-green algae, cyanobacteria) were almost certainly responsible for the original transition to the oxygen-containing atmosphere about 2000 million years ago ..."; "By this slow, inexorable process of photosynthesis (by blue-greens) the early atmosphere was modified; gasp by gasp, oxygen was added, and carbon dioxide commensurately reduced. It was life processes that shaped the atmosphere, that paved the way for other more advanced organisms."28; "While we know that oxygen began to accumulate in the Earth's atmosphere around 2 billion years ago, we do not know how much there was. There could have been plenty, as today, or only a little."29
II: Late Proterozoic: The Vendian -Ediacaran Period.
Climate.
Second Ice Age: .. "from about 950 million years ago until 615 million years ago, parts of what are now Africa, Australia and Europe lay beneath the ice."30; From 2bya .. "a period more or less free of ice for 1000 million years after that followed by frequent peaks of glaciation during the past 1000 million years. Of these peaks, the two with the most secure claim to be called worldwide glaciations - 'true' ice ages - occurred between 700 and 600 million years ago, and between 250 and 230 million years ago."31; "The latest precambrian was a time of many changes. A supercontinent, created earlier .. began to break up about 800my ago. As it did a series of glacial episodes ended with the harshest ice age in the Earth's history. It left glacial deposits in australia about 600my ago when that continent was within 10 degrees of the late precambrian equator."32 
The Rise of Animals (Ediacara fauna).
"Their decline (Cyanobacteria) coincided in timing with the rise of the ediacaran faunas which had no Carbonate skeletons."33; "The Ediacaran faunas have no hard parts, no CaCO3 skeletons."34; .. "the eukaryotic take-off about 1 billion years ago .. Yet no metazoans - multicellular animals - appear in the rocks of the fossil record until about 600my ago, a silence of hundreds of millions of years ..."35; "The first traces of metazoan (multicellular) animal life are recorded in the later Proterozoic; for example, the 670 Ma old Ediacara fauna from sandstones of central Australia. These are soft bodied ancestors of a wide range of animals that started secreting skeletons around the Cambrian-Precambrian boundary. Many of them were filter feeders and scavengers of the sea bottom; others were floating micro-carnivores. They include primitive arthropods, sea-pens, jellyfish, worms and sea-urchins."36; "Right from the start, the rise of metazoans put evolutionary science in a quandry. Cambrian rocks no older than 550my contained the earliest animal fossil record - arthopods, mollusks, brachiopods, and others. Below them there were no animal fossils."37
Climate and Photosynthesizers.
It could be that Photosynthesizers helped to trigger off an ice age in the early proterozoic but later provoked a period of global warming, "Photosynthesizers had drawn down so heavily on the greenhouse gas, carbon dioxide, that they nearly caused the planet to freeze over. And in drawing down the carbon dioxide they must have released much more oxygen into the atmosphere."38; "Their decline (Cyanobacteria) coincided in timing with the rise of the ediacaran faunas which had no Carbonate skeletons. The change in the mode of Carbon-cycling may have started the warming trend after the proterozoic glaciation."39
Atmospheric Oxygen.
The level of oxygen in the Earth's atmosphere is a good indication of the state of the Earth's Photosynthetic capacity. The proterozoic saw the development of an oxygen atmosphere. It has been suggested that even 1500 million years ago the Earth's Photosynthesizers had boosted the level of atmospheric oxygen, "By 1500 Ma ago, atmospheric oxygen may have risen to 15% of its present level."40 However, according to lovelock, "The proterozoic period .. is poorly understood. Scientists know that for the most part it was a world of micro-organisms like the archean. Unicellular life was hardly vigorous enough to bury the larger quantities of Carbon needed to sustain a high level of oxygen by counteracting its rapid removal by reaction with the rocks. I think that oxygen did not increase much above 1% until the evolution of large plants and Animals."41
Geological Developments: Bifs.
"The increasing populations of cyanobacteria on the unlit bottoms of the new shallow seas relentlessly pumped out free oxygen, and the Earth rusted. From 2.2 to 1.8 billion years ago, huge volumes of banded iron formations were laid down. The massive amounts of reduced iron that had accumulated in the oceans rusted and precipitated to the bottom. Once the reduced iron ran out, there was no other chemical sink big enough to hold the continuing bilogical surge of oxygen and this gas built up, first dissolved in water and then escaping into the atmosphere."42; "But what kind of photosynthesis were the organisms using? A vital marker is the estimated 600 trillion tons of iron ore composing the banded iron formations (bifs) that are today Earth's key commercial source of iron. Bifs are marine rocks in which layers of iron-rich sediment alternate with iron-poor layers of other minerals. Only an alien Earth nearly free of molecular oxygen could lay them down. This is because reduced iron (oxygen-free) will dissolve in seawater, but oxidized iron - familiar rust - will not dissove and will precipitate rapidly. Bifs indicate a cycle of activity, in which some possibly seasonal photosynthesizing agency turned up the oxygen supply, and rusted the iron dissolved in the primitive seas. Most of our bifs were deposited between 2.5 and 1.8 billion years ago ..."43 This implies there couldn't have been any excess oxygen in the atmosphere until after 1.8 billion years.
v) The Phanerozoic (570 mya to present).
This is the era known as the age of visible life. Some commentators do not use this classification.
vi) The Paleozoic Era (570-245 mya).
- The Cambrian Period (570-510 mya).
- The Ordovician Period (510-439 mya).
- The Silurian Period (439-409 mya).
- The Devonian Period (409-363 mya).
- The Carboniferous Period (363-290 mya).
- The Permian Period (290-245 mya).
I: The Cambrian Period (570-510 mya).
Photosynthesizers (Skeletal [Calcareous] Eukaryotes; Trilobites). "During the cambrian one-third of the world was devoid of life. The barren area was the land surface away from the sea."44; "The second major development was the 'Cambrian explosion' about 600 Ma ago. The trilobites, and other calcareous organisms, came suddenly onto the scene. Two big steps forward in biological evolution were taken prior to the beginning of the Cambrian, when the first trilobites appeared."45
Climate and Photosynthesizers.
"The cambrian explosion was an event when skeletal eukaryotes usurped the function of prokaryotes in removing greenhouse CO2 through CaCO3 precipitation."46; "While the evolution of Ediacaran faunas may have been related in some way to climate, the sudden appearance of calcareous organisms at the beginning of the Cambrian could not be correlated to strong climatic signals. The Cambrian explosion took place in the midst of an apparently warming trend, while the stromatolitic community declined."47
Wildlife.
.. "at the end of the precambrian there was a revolution. Within a few million years Animals with shells appeared, and, what is more, a considerable variety of them."48; "In just 35 million years .. animal life erupted in an explosion of inventiveness that far outshines anything the Planet has seen before or since. During the preceding three billion years of life on Earth, the most sophisticated creatures evolution could come up with were .. algae, the mysterious ediacarans and perhaps flatworms. Them, with little warning, at least little that left any trace in the fossil record, all hell broke loose. Early in the cambrian period about 535 million years ago, large, diverse and lavishly elaborate Animals suddenly appeared. Then it all stopped, as abruptly as it started. The palaeontologists struggling to explain the cambrian explosion face a tough task .. Until recently their only option was to study the Animal fossil record. But now, more and more researcher are taking a different path to enlightenment: scrutinizing the genetic record that has been handed down through the ages to today's creatures.."49
II: The Ordovician Period (510-439 mya).
Climate - Ice age, 430 mya.
.. "a little known ice age, 430 million years ago .. There is evidence around the world of a massive deterioration of climate as the ordovician period drew to a close. It became colder and colder. Trilobites that had, until then, only lived in the polar regions suddenly moved into lower latitudes. As a result of the climatic change, many kinds of Animals became extinct; in fact, well over half of all species previously living. It was not the first (ice age), nor will it be the last, and nobody knows its cause."50; "It is probable, but not certain, that North Africa was covered by an ice sheet about 450 million years ago."51; "A bit less than 500 million years ago glaciers were active in what is now the Sahara Desert, while it lay at the South Pole. Africa and North America were then about 10,000 kilometres apart."52
Photosynthesizers.
"Presumably, there must have been enough oxygen in the atmosphere of the ordovician to start such a protective process, the long patient result of 3,000 million years of algae and 'blue-green' bacteria releasing oxygen into the atmosphere."53; "The ancestors of all land plants are green algae. These photosynthesizers had certainly adapted to freshwater rivers, lakes, and ponds before the end of the ordovician, and perhaps much earlier. Freshwaters contained the carbon dioxide they needed, as well as phosphates and nitrates essential for constructing necessary biomolecules."54 
III: The Silurian Period (439-409 mya).
The Rise of Terrestrial Photosynthesizers.
It has been argued that, "From green algal cells (protoctists) came the cells of plants."55 The rise of terrestrial Photosynthesizers was a long process, "The landward transformations were probably already underway in the silurian, but were completed in the devonian period - that is, between 410-360 mya."56; "The first plants moved on to land during the silurian period, with simple small forms like Cooksonia ..."57; "The earliest known vascular plant are named cooksonia, and come from the upper silurian."58; "Bacterial Photosynthesis was followed by another version of the process, using a different kind of chlorophyll, and it was this type of Photosynthesis that led to the evolution of green plants. The essential difference is that in plant Photosynthesis the hydrogen is obtained, not from hydrogen sulphide, but from the photolysis (breakdown using light energy) of water."59
IV: The Devonian Period (409-363 mya).
Photosynthesizers; The Greening of the Land; The Rise of Forests.
"There have been many changes since the greening of the Earth in the devonian."60; "The next milestone in evolution was the rise of land Plants. From a few species of vascular Plants of primitive morphologies in silurian and devonian time ..."61 Trees have not always existed on Earth. Although it is difficult imagining the Earth without them they are a relatively recent climatic innovation, "The first Forests, some 400 million years ago, heralded the proliferation of new life-forms. The great Trees of the Carboniferous era 320-210 million years ago laid down the coal that fired the industrial revolution .. ."62; "The plants that died and eventually were converted into coal grew at various times in the past. Some lived more than 400 million years ago, but most were growing about 300 million years ago."63
V: The Carboniferous Period (345-280 mya).
Climate - Late Carboniferous Ice Age.
"South africa, south america, india and australia were partly covered by ice for a long time, between about 350 million years ago and about 250 million years ago, though not continuously. This episode was at the end of the Carboniferous and commencement of the Permian periods, and it was at about the time that Pangaea began to break into two supercontinents. So far as anyone can tell, the great Carboniferous-Permian ice age that occurred around 290 million years ago was the last for a very long time. For most of its history the Earth has been free from year round ice .."64; "It used to be thought that there had only been four or five ice ages, and all within the last one or two million years. Now it is clear that ice ages occurred much earlier in the Carboniferous period and the Permian period and that there were many of them, interspersed with warmer interglacials."65; "It is obvious that the sea must have advanced over the Carboniferous coal swamps when the dark rocks were formed. This drowning must have killed trees, amphibians and scorpions alike. But it did not do permanent damage .. Why this happened is not agreed. At certain times it is obviously connected with the ebb and flow of an ice cap; (but the inundations were global). This immersion of coal swamps halted the abundance of photosynthesis for a short while, reinstating the ancient dominance of the sea."66
Photosynthesizers, The Rise of Gymnosperms.
"The plants that died and eventually were converted into coal grew at various times in the past. Some lived more than 400 million years ago, but most were growing about 300 million years ago. They grew, all of them, as swamp forests and such forests occur only in the kind of warm, humid climates we associate today with equatorial regions. Clearly the Forests extended over vast areas - across much of what are now North America, Europe and Asia, for example - and this suggests that the Earth has experienced several periods when the climate over these large areas was a great deal warmer than it is now."67; "The next milestone in evolution was the rise of land plants. From a few species of vascular plants of primitive morphologies in silurian and devonian time, more than 300 species are found in the Carboniferous fossil record, including the first big Trees called gymnosperms. Their production was so rapid that the swampy environment of their growth would soon become oxygen deficient. Some of the organic Carbon is preserved in the form of thick coal seams."68
Climate and Photosynthesizers.
During the creation of coal deposits during the Carboniferous, "Gaia had never been such a spendthrift since the proterozoic. We can imagine that the atmospheric CO2 was again depleted: continental glaciers covered gondwanaland at the beginning of permian time. Gaia was again freezing, and she had to build a better greenhouse."69
VI: The Permian Period (290-245 mya).
Continents.
.. "all the world's continents were once united as a single entity (pangaea) in the late permian ."Climate.
"Several hundred million years ago, the earth may have been up to 20C warmer than it is today, with no ice on both poles. In that time period, the planet moved through an ice age that produced glaciers in the inland areas of the tropical regions of Africa, India and South America."; "As the various parts of pangaea converged, eventually to be pieced together into the supercontinent, so the climate deteriorated. Glaciation was under way by the end of the Carboniferous and extended into the permian; it was the first time the world had suffered the advance of continental glaciers since the extinction which had ended the ordovician. The detailed evidence shows a complex series of ice sheets that waxed and waned by turn."72; "A glacial episode at the end of the permian .. Some evidence for glacial conditions is that sea levels appear to have dipped and risen every 2.5 my during the mid- and late permian, possibly as a result of cyclically active ice ages."73; "Inorganic 13C can also be taken out of circulation by being locked into various forms of calcite (calcium carbonate: CaCO3), either in the skeletons of marine organisms or in limestones. Measurements of the proportions of the two isotopes have been made (in many areas around the world). They record a sharp rise in the ratio of 13C to 12C that comes in the latest permian and is followed by a steep drop across the P-Tr boundary. The rise is caused by the removal of organic carbon buried in the coal levels that built up during much of the permian just as they had done in the late carboniferous. The drop indicates either the disappearance of a vast amount of 13C, or the reappearance of 12C. How can these alternative be explained? Tony hallam and paul wignall believe that falling sea levels in the permian exposed huge areas of land to chemical weathering. In particular they think that the organic carbon previously buried in coal deposits reacted with atmospheric oxygen to produce a great increase in the volume of carbon dioxide, and of course to reduce the volume of free oxygen. Oxygen isotopes measured in the same samples also show an abrupt peak in the late permian followed by the same sharp decline just before the P-Tr boundary and lasting well into the triassic. It has been estimated that the level of atmospheric oxygen fell from a normal value of about 30% to as little as 15%. With so much less oxygen left in the air, the supply to the sea was inevitably reduced, and this is recorded in deposits such as black shales and pyrites, which can only be formed in the absence of oxygen."74 (The loss of so much oxygen led to a massive extinction of many Animals); "For 250 million years, throughout the age of the dinosaurs, the earth was warm and wet, almost tropical."75
Photosynthesizers (C3s).
"Ancient plants such as cotton, wheat, roses and strawberries, classified as C3, go back to 300 million years when the Earth's atmosphere contained much less carbon dioxide. "76
Climate and Photosynthesizers.
"With the evolution of land plants, coal-makers took over the 'air conditioning' duty. They over-did it, and Permo-Carboniferous glaciation ensued. After a wholesale turnover of the faunas and floras at the end of the Palaeozic, more CO2 was released than fixed in early Mesozoic time."77; "We can imagine that the atmospheric CO2 was again depleted: continental glaciers covered Gondwanaland at the beginning of Permian time. Gaia was again freezing, and she had to build a better greenhouse."
Wildlfe; the Permian Extinctions.
"Nor is there any question that the greatest of all extinctions happened at the time of pangaea. This was probably a double event, with a massive loss towards the end of the permian, about 250 million years ago, and another close to the end of the triassic, about 10 million years later. I find it difficult to comprehend the magnitude of the change that happened through this interval. It reset evolutionary history. A narrative that had run from the end of the ordovician was drastically halted. Yet the end of the permian saw the reconstruction of the natural world. It was, truly, a mass extinction, a carnage of a magnitude that had never troubled the earth before. Trilobites were never seen again. The fusiulinids completely disappeared. The calcite corals were eliminated entirely. The litany of disappearances runs on. But this did not take place as the result of one single catstrophe. Nobody disputes the facts, but the cause is quite another matter."79; .. "animals in the oceans suffered the great permian mass extinction, another poorly understood event that devastated the fauna, extinguishing at least 95% of ocean species."80
vii)The Mesozoic Era (245-65 mya).
- The Triassic Period (245-208 mya).
- The Jurassic Period (208-146 mya).
- The Cretaceous Period (146-65 mya).
I: The Triassic (245-208 mya).
The Continents.
"At the close of the Palaeozoic era all the continental crust was clumped into one mass named Pangaea."81
Climate - A Global Ice Age followed by Warming.
.. "worldwide glaciations - 'true' ice ages - occurred between between 250 and 230 million years ago."82; "The continent grew into a Pangaea towards the beginning of the triassic ... The climate was warming up in triassic and jurassic time."83Photosynthesizers (Coccolithophorids).
"The most numerous of these (shell-forming) organisms are algae - plants, although they move about as animals do - known as coccolithophorids. Their calcareous plates are called 'coccoliths'. Coccolithophorids became very abundant some 200 million years ago and have remained so ever since."84
Climate and Photosynthesizers.
"The continent grew into a Pangaea towards the beginning of the triassic, and the interior of that supercontinent was a giant desert, where few trees grew. Carbon fixation by plants was reduced to a minimum, and increased terrestrial erosion may have set free much fossil Carbon in circulation. The climate was warming up in triassic and jurassic time."85
Wildlife.
"The reign of the reptiles had been a long one. They had come to power about 250 million years ago."86; "Nor is there any question that the greatest of all extinctions happened at the time of pangaea. This was probably a double event, with a massive loss towards the end of the permian, about 250 million years ago, and another close to the end of the triassic, about 10 million years later."87
II: The Jurassic (208-146 mya).
III: The Cretaceous (146-65 mya).
Climate - The Warming of the Early Cretaceous.
"The mid- and early Cretaceous appears to have been significantly warmer than the late Cretaceous."88; "The Cretaceous was a time of global warmth when the Earth's climate was in an extreme 'greenhouse' mode. Fossil evidence for this is varied but the most obvious manifestation is extensive forests at very high (75-80) paleolatitudes."89; "A greenhouse climate prevailed during the early cretaceous, but there were, however, cooling episodes, or even glacial interludes and the trend was definitely reversed sometime during the middle Cretaceous.."90
Climate - The Cooling of the Late Cretaceous.
"Both vegetational and marine oxygen isotope data suggest that the late Cretaceous was a time of declining temperature."91; "Vegetational evidence suggests that there was no significant permanent ice at the poles during the late Cretaceous. This idea is supported by high latitude oxygen isotope data which indicate that the region around James Ross Island in the antarctic experienced a cool temperate climate. The likelihood is that the warm, equable climate of the Cretaceous Period was a function of continents clustered mainly in the low latitudes and high CO2 levels."92
Photosynthesizers - Flowering Plants (Angiosperms), Calcareous Plankton.
"The oldest angiosperm fossil dates from the middle of the early cretaceous, about 130 to 120my ago."93; "During the early cretaceous gymnosperms continued to dominate the flora of the land, but the cycads and ginkgoes were in severe decline, the bennettitaleans heading for extinction, and only the conifers were really prospering. The angiosperms - flowering plants, hardwood trees, and very much later the grasses - arose sometime in the mid-cretaceous, about 100my ago."94; "During the late cretaceous, the angiosperms diversified further, until by the end of the period about 50 modern families (out of a total 500) had made their appearance, among them beech, birch, fig, holly, magnolia, oak, palm, sycamore, walnut, and willow."95; "Prior to the arrival of the angiosperms the Arctic forests were rich in conifers, ginkgophytes, ferns, and even cycads."96; "The cretaceous was when flowering plants (angiosperms) became an important part of the flora."97; "The most significant advances of Mesozic life history are the rise of the flowering plants on land, and the evolution of calcareous plankton in the ocean. .. they did not constitute significant fractions of the global biomass until Cretaceous time.."98
Climate and Photosynthesizers.
"The warming trend reached its zenith in the early Cretaceous, when flowering trees and calcareous plankton began to flourish. The decline since then, with a temporary restoration during early Palaeogene time, could be a manifestation of the varying efficiency of extracting and burying carbon dioxide in the form of inorganic and organic carbon."99; "It appears that the widely recognized late Cretaceous cooling may have its origins in a decline in atmospheric carbon dioxide due to enhanced productivity in surface waters."100; "The rise of the angiosperms may have also contributed to global cooling during the last 100 million years. Volk suggested that the spread of angiosperm-deciduous ecosystems had caused a higher rate of global weathering, and thus increased fluxes of Ca and Mg ions from continental silicates contributed to the increasing importance of calcareous plankton. The plankton precipitation in turn depleted the atmospheric carbon dioxide."101
viii) The Cenozoic Era (65 mya - present).
The cenozoic era is divided into two main periods:-- I: The Paleogene Period (65mybp-23mybp).
- II: The Neogene Period (23 mybp-present).
I: The Paleogene Period (65-23mya).
The paleogene period is divided into three main periods:-- I.A: The Paleocene Period (65-57 mybp).
- I.B: The Eocene Period (57-34 mybp).
- I.C: The Oligocene Period (34-23 mybp).
I.A: The Palaeocene Period (65-57 mya).
Continents.
"Towards the end of the dinosaur's reign, (65 million years ago) this great land (pangaea) split into two - a northern supercontinent comprising today's Europe, Asia, and North America; and in the south, another made up of South America, Africa, Antarctica and Australia."102Climate - Rising Temperatures.
"The steady temperature decline since middle Cretaceous time came to an abrupt halt at the end of the cretaceous, and the palaeocene started with a steady rise. The temporary reversal was halted early in middle Eocene time, when step-like decreases of ocean temperature continued except for minor oscillations."103
I.B: The Eocene Period (57-34 mya).
Climate.
"The most recent ice age era began about 66 million years ago, at the time of the mass extinction that included the dinosaurs. Mild at first, about 55 million years ago small glaciers began to grow in anarctica."104Photosynthesizers.
"More recent plants, C4s such as maize, sorghum and sugar cane, are 40-50 million years old and more adapted to modern conditions."105
I.C: The Oligocene Period (34-23 mya).
II: The Neogene Period (23 mya-present).
The paleogene period is divided into four main periods:-- II.A: The Miocene Epoch (23-5 mya).
- II.B: The Pliocene Epoch (5-1.6 mya).
- II.C: The Pleistocene Epoch (1.6mya-10,000ya).
- II.D: The Holocene Epoch (10,000ya-the present).
II.A: The Miocene Epoch (23-5 mya).
Climate.
During the oligocene/miocene period .. "the global average surface air temperature was about 6C warmer than today."106; "(There was a) dome-shaped ice sheet that by 20 million years ago covered the whole continent (of antarctica)."107; "Antarctic glaciation started in the late Eocene or early Oligocene, and the polar ice cap expanded during the middle Miocene."108; "For 250 million years, throughout the age of the dinosaurs, the earth was warm and wet, almost tropical. Then around 40 million years ago, the planet began to cool. Around 15 million years ago, the Earth cooled even more ..."109; "About 8 million years after that (12mya), alaska started to be glaciated ..."110
Photosynthesizers (Calcareous plankton, C4s).
"Not surprising is the emergence in the Miocene, some 10 million years ago, of a new type of green plant able to grow at lower Carbon dioxide concentrations. The new C4 plants include some, but not all grasses, whereas trees and broad leaved plants generally use the C3 cycle."111
Climate and Photosynthesizers.
"Now fully recovered from the Cretaceous-Tertiary catastrophe, the ocean calcareous plankton resumed their efficiency in reducing the level of atmospheric CO2."112Wildlife.
"The appearance of grasses in the tertiary was of crucial importance to the modern mammal fauna, for many of the animals that figure prominently in human history feed, predominantly, upon grass. Grasslands finally took over large tract of the world during the miocene .. the great grasslands, savannah, prairie and pampas, date back to this period."113
II.B: The Pliocene Epoch (5-3 mya).
Climate.
"Moving toward the present, the next warming peak (after the oligocene/miocene period) occurred during the Pliocene. In that period, the Earth was about 4C warmer than today."114
II.C: The Pleistocene Epoch (2.4 mya - 10,000 ybp).
Climate - The Cause of the Pleistocene Ice Ages/Inter-glacials.
"What caused the final sudden cooling of the world in the pleistocene that led to the start of the ice age about 2my ago? One significant event seems to have been the north-south american connection established about 2.5 my ago. It disrupted patterns of oceanic and atmospheric circulation, and in particular it sent northward some warmer ocean currents that would previously have flowed further south. It takes plenty of atmospheric water to build new glaciers, and this can be provided by the rainfall associated with warm currents along continental margins. This event seems to be linked with the creation of the arctic icecap and the formation of cold currents around the north pole. The rythm of these cold periods is related to a combination of three planetary cycles that affect the amount of solar radiation that the Earth receives. These cycles have probably influenced the Earth's climate throughout its history, but it took the formation of the arctic icecap to enable them to tip the global system into a series of ice ages, not yet concluded."115
Climate - The Start of the Pleistocene Ice Ages/Inter-glacials.
Despite the sun's increasing luminosity over the aeons, the Earth has not become hotter. On the contrary, over the last few million years, the Earth's climate has oscillated between ice ages and inter-glacials, "Ice ages tend to last for 100,000 years. The spell between them, usually, lasts for 10,000 years."116 "The Pliocene Epoch - had been generally warm but the Pleistocene brought dramatic changes. At its most extreme, ice covered about 28% of the land area of the Earth - at present it covers 10.4%."117
There are disagreements about the start of this recent succession of ice ages. Some commentators argue they started five million years ago, "For the past five million years, the climate of our planet has followed a rhythm in which ice ages of about 100 thousand years are separated by 'interglacial periods' about 15,000 years long."118.Some commentators argue they started three million years ago, "It is only in the past 3 million years or so that ice caps have formed over the poles .."119; "Not long before the start of the ice ages, about 3 million years ago, certain fossils suggest that the world must have been much warmer than it has been at any time since."120 Other commentators argue for two and a half million, "The world as we know it, with ice on both poles and glaciers on the highest mountains, came into existence as recently as 2.5 mybp."121; "by 3 million years ago, greenland lay beneath an ice sheet. Around two and a half million years ago .. the pleistocene began."122; "The last ice age started 2.5 Ma ago in the northern hemisphere. There were glacial and interglacial stages, and there were times of more or less greenhouse CO2 in the atmosphere"123 Some commentators believe the ice ages are a more recent phenomenon, "The present oscillations to and from a glacial state are recent: up until 2 million years ago, the climate was much more constant."124; "About 2 million years ago, or possibly a little earlier, the world entered a new ice age."125 Finally, there are commentators wwho believe that the ice ages have a much shorter duration, "The waxing and waning of ice sheets during the last 1.5 million years forced great migrations upon animals."126
Climate - Number of Glacials/Interglacials.
Some commentators argue there have been about 20 interglacials, "By comparison with the previous history of the earth, the last 2 million years were remarkably steady in climate, and significantly cooler on average. Data for the last 850,000 years indicate that over this time period, the average temperature of the northern hemisphere was about 15.5C. It is this cooler climate that has spawned most of the present-day biotic life. The appearance of the first human beings on Earth also coincides with the beginning of this period. Within the Pleistocene, about twenty glacial and inter-glacial periods occurred that alternated roughly every 100,000 years."127 Other commentators argue for four interglacials, "There were four major ice ages during the Pleistocene, separated by interglacials."128
The Fourth or Wurm Glaciation (70,000 - 40,000 ya).
.. "the first part of the fourth or Wurm glaciation (70,000 - 40,000ya) .."129
The Eem-Sangamon Interglacial (125,000 ya).
"The warmest peak (in the recent period of interglacials) occurred about 125,000 years ago (the Eem-Sangamon interglacial) when it was about 2-2.5C warmer than today."130
The Eemian??????
"The holocene has only had one climate state, but it appears that the Eemian had three - one like the one we have now, one warmer and one colder. It appears also that a shift from one climate state to another took very little time, perhaps less than ten years."131
The End of the Last Ice Age, 20,000-10,000 ya.
"The most recent ice age was at its coldest 20,000 years ago. It began to relent about 15,000 years ago .. "132; .. "the end of the ice age was by no means a smooth, uninterrupted warming. The warming began about 18,000 years ago and continued for about 5,000 years. Then it was interrupted. Temperatures plummeted and, for about 1,000 years, almost glacial conditions returned. Towards its end, between about 12,500 and 12,100 years ago, there seems to have been a short period of warming and cooling again before the general warming resumed. For the next 1000 years or so, the world grew warmer but then there was a second interruption and a second period, this time lasting for about 500 years, from 10,800 to 10,300 years ago, during which the climate was almost glacial."133 "The last of these shorter inter-glacials - a warm period the earth is still experiencing now - began about 12,000ybp."134; "During this period (the last ice age) the whole of scandinavia, north germany, poland, north-west soviet union and most of Britain were covered in ice and at the height of the glacial period, about 20,000 years ago, the ice sheets moved even further south. The area to the south of these ice sheets was one of permafrost and a tundra type vegetation. It supported a wide variety of animal life dominated by herds of reindeer, woolly mammoth, bison and wild horse together with smaller numbers of woolly rhinoceroses, giant elk and saiga antelope."135
The Younger Dryas, 12,900-11,600 ya.
"The Earth suddenly swung back into a cold spell between 12,900 and 11,600 years ago. This cold snap is known as the Younger Dryas."136
Wildlife.
.. "by about a hundred thousand years ago and during most of the first part of the fourth or Wurm glaciation western Europe was occupied by Homo Sapiens neanderthalenis."137; "It is now clear that people of this kind, much more like ourselves than the classic Neanderthals, were in existence in Africa, and probably elsewhere, 60-100,000 years ago, when the neanderthals were still occupying Europe."138; "By around 40,000 years ago, between the first and second phases of the Fourth or Wurm glaciation, another type of human being had appeared in Europe. Homo sapiens sapiens."139; .. "a species which can be genuinely identified with ourselves originated as recently as 40,000 years ago."140; "The ice age of the pleistocene is the third one i have described in this history; in geological terms, we have only just emerged from it. The waxing and waning of ice sheets during the last 1.5 million years forced great migrations upon animals."141
Photosyntheizers.
"In the world at the height of the last glaciation, about 18,000 years ago, the global water tied up and useless in a frozen state led to arid conditions in the tropics. The tropical forests shrank to an area less than they occupied just after the last ice age and just before humans became farmers. It is not hard to see how the larger mammals of australia and madagascar with their adaptations to tropical forest living would have been pushed to the edge of extinction, and often past it, by the encroaching deserts, while the forest animals in the rest of the tropics would find themselves squeezed into shrinking refuges where scarcity might force direct competition and extinctions. The term 'ice ages' therefore distracts attention from the chief agent of change. The drying of the tropics may have had a much more profound effect on mammalian evolution and extinctions than the freezing of the ice sheets."142
II.D: The Holocene Epoch (The Interglacial of the Last 10,000 Years).
The current inter-glacial period is called the holocene, "The earth has enjoyed a rather steady climate over the last 10,000 years in the current interglacial, and the Ice Age before that lasted about 100,000 years. .. The Holocene has only had one climate state ..."143
ix) Conclusions.
I: The Overall Stability of the Earth's Climate.
Whilst some commentators argue the climate has been stable over the last 3.6 billion years, others tend to stress the instability, "The climate on earth has changed throughout the evolution of our planetary system over about 4500 million years."144
