Page6

Universidade Fernando Pessoa

Porto, Portugal

Plate 56- Without CO2 there will be no photosynthesis and without photosynthesis no life could be possible in the Earth. The photosynthesis (http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html) is the process by which plants, some bacteria, and some protists use the energy from sunlight to produce sugar, which during the night, cellular respiration (transfer of energy from sugar molecules a multifunctional nucleotide by consuming oxygen and generating CO2), converts into adenosine triphosphate - ATP, the "fuel" used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll. Most of the time, the photosynthetic process uses water and CO2 and releases oxygen that we absolutely must have to stay alive. In addition, we need the food as well. The overall reaction of this process can be written as: 6H2O + 6CO2---------->C6H12O6+ 6O2 or six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen. Subsequently, CO2 is absolutely necessary in the atmosphere and plants may be viewed as carbon sinks, removing CO2 from the atmosphere and oceans by fixing it into organic chemicals. Plants also produce some CO2 by their respiration, but this is quickly used by photosynthesis. Plants also convert energy from light into chemical energy of C-C covalent bonds. Animals are CO2 producers that derive their energy from carbohydrates and other chemicals produced by plants by the process of photosynthesis. The balance between the plant CO2 removal and animal CO2 generation is equalized also by the formation of carbonates in the oceans. This removes excess CO2 from the air and water (both of which are in equilibrium with regard to CO2). Fossil fuels, such as petroleum, gas and coal, as well as more recent fuels such as peat and wood, generate carbon dioxide when burned. Fossil fuels are formed ultimately by organic processes, and represent also a tremendous carbon sink. Human activity has greatly increased the concentration of CO2 in air (see next plate).

Plate 57- During the carbon cycle, autotrophs (organisms that are able to form nutritional organic substances from simple inorganic substances such as carbon dioxide) acquire CO2 from the atmosphere by diffusion through leaf stomata (minute pores in the epidermis of the leaf or stem of a plant), incorporating it into their biomass. Some of this becomes a carbon source for consumers and respiration returns CO2 to the atmosphere. Photosynthesis and cellular respiration form a link between the atmosphere and terrestrial environments. Carbon cycles in the environment very quickly. Plants have a high demand for CO2, yet CO2 is present in the atmosphere at a low concentration (0.03%). Carbon loss by photosynthesis is balanced by carbon release during respiration. Some carbon is diverted from cycling for longer periods of time, as when it accumulates in wood or other durable organic material. Decomposition eventually recycles this carbon to the atmosphere. However, carbon can be diverted for millions of years, such as in the formation of coal and petroleum. The ocean contains about 50 times the amount of carbon (in various inorganic forms) as is available in the atmosphere. It important to know that during, and immediately after, the breakup of the supercontinents (Proto-Pangea and Pangea) a lot of CO2 was integrated into the atmosphere coming from the subaerial expansion centers associated with the SDRs, i.e., the subaerial lava flows. Similarly, when the subaerial expansion centers become submerged, to create the oceanic crust, a significant amount of CO2 is incorporated in the oceans.

Plate 58- Carbon is exchanged, or “cycled” among Earth‘s oceans, atmosphere, ecosystem, and geosphere (term often used to refer to the densest parts of Earth, which consist mostly of rock and regolith). All living organisms are built of carbon compounds. It is the fundamental building block of life and an important component of many chemical processes. It is present in the atmosphere primarily as carbon dioxide (CO2), but also as other less abundant but climatically significant gases, such as methane (CH4). Because carbon compounds, which are oxidized to CO2, fuel life processes the latter is exhaled by all animals and plants. Conversely, plants assimilate CO2 during photosynthesis to build new carbon compounds. CO2 is produced by the burning of fossil fuels, which derive from the preserved products of ancient photosynthesis. The atmosphere exchanges CO2 continuously with the oceans. Regions or processes, which predominately produce CO2 are called sources of atmospheric CO2, while those that absorb CO2 are called sinks. The anthropogenic CO2 flux is meaningless when compared with the natural CO2 flux. The majority of the geoscientists nowadays consider Earth, as an open system far-from-equilibrium and self organized critically, i.e. a dissipative structure using Prigogine's terminology. It receives a continuous flux of matter or energy from the sun which allows it to survive, i.e. to encounter instabilities leading to new forms of order that move it farther and farther away from the equilibrium state, that means, away from death. A process of self-regulation is the key of Lovelock's Gaia theory. Lovelock knew, from astrophysics, that the heat of the sun has increased by 25% since life began on Earth. However, in spite of this increasing, Earth's surface temperature has remained more or less constant, at a level comfortable (10°- 22° during Phanerozoic) to life during the past four billion years. He explained this self-regulation by a tight interlocking between the planet's living parts (plants, microorganisms, and animals) and its non-living parts (rocks, oceans and the atmosphere). Such an interlocking does not allows longer to think of rocks, animals and plants as being separated.

Plate 59- The numbers above are quite meaningful. They are not very good for those who dream of an egalitarian society based on rejection of economic growth in favour of a smaller population eating lower on the food chain, consuming a lot less, and sharing a much lower level of resources much more equally. A. Wild as ky (Professor at the UC Berkeley) said: "Warming, and warming alone, through its primary antidote of withdrawing carbon from production and consumption, is capable of realizing the environmentalist's dream" (quoted in http://www.reason.com/news/show/36048.html). In fact, for an annual economical growth of 3 % a total of ± 0.09 GtC would be added every year, i.e., one third of the carbon release in the atmosphere by human breathing. In spite of the fact that man’s contribution is quite small, the "alarmists" advance a positive feedback and it is such a conjecture that divides the scientists. In 1996, Capra (The Web of Life: a new understanding of living systems. Anchor books, Doubleday. New York 10036) gave a nice (but not too accurate, see next plate) illustration of the interconnections between living and non living parts of Earth using the CO2 cycle: “The Earth's volcanoes have spewed out huge amounts of carbon dioxide (CO2) for millions of years. Since CO2 is one of the main greenhouse gases, Gaia needs to pump it out of the atmosphere; otherwise it would get too hot for life. Plants and animals recycle massive amounts of CO2 and oxygen in the processes of photo-synthesis, respiration, and decay. However, these exchanges are always balanced and do not affect the level of CO2 in the atmosphere. According to the Gaia theory, excess carbon dioxide in the atmosphere is removed and recycled by a vast feedback loop, which involves rock weathering as a key ingredient. In the process of weathering, rocks combine with rainwater and carbon dioxide to form various chemicals, called carbonates. The CO2 is thus taken out of the atmosphere and bound in liquid solutions. These are purely chemical processes that do not require the participation of life. However, Lovelock and others discovered that the presence of soil bacteria vastly increases the rate of rock weathering. In a sense, these soil bacteria act as catalysts for the process of rock weathering, and the entire carbon dioxide cycle could be viewed as the biological equivalent of the catalytic cycles studied by Manfred Eigen. The carbonates are then washed down into the ocean, where tiny algae, invisible to the naked eye, absorb them and use them to make exquisite shells of chalk (calcium carbonate). So the CO2 that was in the atmosphere has now ended up in the shells of those minute algae. In addition, ocean algae also absorb carbon dioxide directly from the air. When algae die, their shells rain down to the ocean floor, where they form massive sediments of limestone (another form of calcium carbonate). Because of their enormous weight, the limestone melt and may even trigger the movements of tectonic plates. Eventually some of the CO2 contained in the molten rocks is spewed out again by volcanoes and sent on another round in the great Gaia Cycle. The entire cycle - linking volcanoes to rock weathering, to soil bacteria, to oceanic algae, to limestone, and back to volcanoes - acts as a giant feedback loop, which contributes to the regulation of the Earth's temperature. As the sun gets hotter, bacterial action in the soil is stimulated, which increases the rate of rock weathering. This in turn pumps more CO2 out of the atmosphere and thus cools the planet”.

Plate 60- Life exists since the Precambrian, which ended with the agglutination of several tectonic plates to form a supercontinent (Rodhinia or Proto-Pangea). The breakup of this supercontinent and the dispersion of the individualized continents was accompanied by a large CO2 degasification event coming from the expansion centers and associated lava flows and pillow lava The CO2 atmospheric content was probably more than 10 times higher than present and all living creatures developed in a healthy or vigorous way, as a the result of a particularly favourable environment. This is particularly important, since it refutes the always advanced "alarmist" conjecture: "since CO2 is one of the main greenhouse gases, Gaia needs to pump it out of the atmosphere; otherwise it would get too hot for life". As illustrated on next plate, during the Phanerozoic, i.e., since ± 600 Ma, the average global temperature was always higher (± 27°) than today (± 15°), and life with a high biodiversity has been always there. However, since Phanerozoic, Earth has experienced five massive species extinctions caused by huge sporadic cataclysms, which induced climatic and physical upheavals: (i) Around 440 Ma, during the Ordovician, when life has not yet reached the continent, it is thought that 60% of the animal and vegetal species disappeared; (ii) Around 367 Ma, during the Devonian, 60% of species have also disappeared; (iii) Around 252 Ma, during the Permian, more than 90% of the species living in the continents and oceans disappeared; (iv) Around 200 Ma, during the Triassic, it is thought that 20% of the species were decimated mainly marine species and the large amphibians; (v) Around 65 Ma, by the end of the Cretaceous, one third of continental species and almost all those living in ocean floor disappeared. The average time duration of one specie is around 5 Ma.

Plate 61- Over the last 540 Ma (Phanerozoic Eon) ancient climates have gone through numerous warm and cool phases, with average temperatures fluctuating from around 12°C up to 22°C. We are presently near 15° C. The Cretaceous Period, (145 to 65 Ma) had the warmest temperatures overall. Then they fell dramatically into the great ice ages. Most of ancient climates of the Mesozoic Era (251 to 65 Ma) were considerably warmer than today. That era included the Triassic, Jurassic and Cretaceous periods. Long before the IPCC could do anything about it. In first half of the Phanerozoic Eon, the Paleozoic Era, one can see dramatic swings between very warm and cold paleoclimate extremes, ending with an ice age that gripped the Carboniferous and Permian periods. These periods collectively spanned 360 to 251 Ma. Before that time, the earth was warmer again, with average temperatures that were warmer than today, i.e., during e Silurian and Devonian periods (444 to 360 Ma). The life during Carboniferous can be summarized as follows (http://www.palaeos.com/ Paleozoic/Carboniferous/Carboniferous.htm): (i) In the oceans coral reefs and invertebrate life flourish, with groups such as brachiopods, echinoderms, ammonites, bryozoa, and corals diversify and are common; among brachiopods, Productids, Spiriferids and Rhynchonellids are abundant; terebratulids are also very common; nautiloid cephalopods are represented by tightly coiled nautilids, with straight shelled and curved shelled forms becoming increasingly rare; ammonoids are common; almost all types being the Goniatites, with suture lines a little more complex than those of the Devonian; trilobites are rare, represented only by the proetids; among echinoderms, blastoids and crinoids are extremely common, especially in the Early Carboniferous (Mississippian); among fish, the armoured placoderm and ostracoderm and marine lobe-finned fish (apart from the odd coelacanths) that so dominated the Devonian seas are all gone, to be replaced by an amazing diversity of sharks (Chondrichthyes); (ii) On land, especially in the Euramerican part of Pangea, the equatorial regions are covered by forests; the moist tropical climate produces a lush plant growth, which eventually becomes the great Coal Deposits; the fern-like but seed-bearing pteridosperms, the huge green-stemmed Lepidodendrale lycopods (35 m tall), the giant sphenopsid Calamites (20 m in height), and the strap-leaved mangrove-rooted Cordaitales (up to 45 m) are all abundant, and tied closely to water; the drier uplands were much more sparsely covered; meanwhile, Gondwanaland, with its colder Antarctic climate, has its own very distinct flora, dominated by glossopterid pteridosperms; (iii) Inhabiting the great forests were many types of insects, spiders, and other types of arthropods evolve; encouraged by the oxygen-rich atmosphere, the abundance of food in the decaying forest leaf-litter, and the absence of large terrestrial vertebrates, many reach huge sizes; the dragonfly-like Meganeura, an aerial predator, had a wingspan of 60 to 75 cm; the inoffensive stocky-bodied and armoured millipede-like Arthropleura was 1.8 m long, and the semi-terrestrial Hibbertopterid eurypterids were perhaps as large, while some scorpions reached 50 or 70cm; Alongside these giants were more conventionally sized invertebrates; (iv) In the water and water margins the tetrapods flourish, are the dominant life form, and many different types inhabit the rivers, ponds, and swamps of the Carboniferous tropics, including many crocodile, eel, and salamander-like forms; but the largest hunters of the time were the gigantic rhizodont fish, reaching 7 m in length. Meanwhile, the first reptiles appear, adapted to life lived totally on land, but remain insignificant until at least the very end of the Carboniferous.

Plate 62- During the Late Carboniferous Period, (± 306 Ma), the Earth's landmasses were arranged as depicted. Many of the continents we know today were already recognizable, some more easily than others. Parts of them were either under water or had not been assembled yet, and almost all were part of one of two larger landmasses known as Gondwana and Laurasia. Antarctica, Africa, Arabia, India, Ceylon, Australia, New Zealand and South America together comprised Gondwana. It was positioned near the South Pole, and during the Late Carboniferous Period was largely buried under large sheets of glacial ice. Europe, Greenland, Siberia, North America, Kazakhstan, and N. China together comprised Laurasia. Pangea is the "supercontinent" created when these two giant landmasses drifted into one another, a process that was complete by the middle of the Permian Period. Later, during the Jurassic Period, the Pangean Supercontinent began to break up and the separate continents once again drifted apart - a process which continues today. During Late Carboniferous time, North America and parts of Europe were in the tropics. The equator stretched from central Colorado to Nova Scotia and also from Great Britain to the Ukraine. Throughout the Late Carboniferous (Pennsylvanian) Period, Pangea drifted northward to drier, cooler climates and by the mid-Permian North America and Northern Europe had become desert-like as continued mountain-building caused much of the interior of the vast Pangean Supercontinent to be in rain shadow. Two special conditions of terrestrial landmass distribution, when they exist concurrently, appear as a sort of common denominator for the occurrence of very long-term simultaneous declines in both global temperature and atmospheric CO2: (i) The existence of a continuous continental landmass stretching from pole to pole, restricting free circulation of polar and tropical waters, and (ii) The existence of a large (south) polar landmass capable of supporting thick glacial ice accumulations. These special conditions existed during the Carboniferous Period, as they do today in our present Quaternary Period. The great Carboniferous Ice Age dominated climate change during the Carboniferous Period. As the Earth alternately cooled then warmed, great sheets of glacial ice thousands of feet thick accumulated, then melted, and then reaccumulated in synchronous cycles. Vast glaciers up to 8000 feet thick existed at the South Pole then, moving from higher elevations to lower, driven by gravity and their tremendous weight. These colossal slow-motion tidal waves of ice destroyed and pulverized everything in their path, scraping the landscape to bare bedrock- altering mountains, valleys, and river courses. Ancient bedrock in Africa, Australia, India and South America show scratches and gouges from this glaciation.

Plate 63- Average global temperatures in the Early Carboniferous Period was around 20° C, although, during the Upper Carboniferous it was much cooler around about 12° C, i.e., comparable to the average global temperature on Earth today. In the Early Carboniferous Period, the atmospheric concentrations of CO2 were roughly 1500 ppm, but by the Middle Carboniferous they declined to about 350 ppm, i.e., comparable to average CO2 concentrations today. Presently, the Earth's atmosphere contains about 380 ppm CO2 (0.038%). Compared to former geologic times, our present atmosphere, like the Late Carboniferous atmosphere, is CO2 impoverished. In the last 600 My, only the Carboniferous Period and our present age (Quaternary Period) have witnessed CO2 levels less than 400 ppm. Geologically speaking, there has been much more CO2 in our atmosphere than exists today. During the Jurassic Period (200 Ma), average CO2 concentrations were about 1800 ppm, i.e., about 4.7 times higher than today. The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Cambrian Period, nearly 7000 ppm (±18 times higher than today). The Carboniferous and Ordovician Period were the only geological periods, during the Paleozoic Era, during which the global temperatures were as low as they are today. To the consternation of "Alarmists", the Late Ordovician Period was also an ice age, while, at the same time, CO2 concentrations were nearly 12 times higher than today (± 4400 ppm). According to greenhouse theory, Earth should have been exceedingly hot, unfortunately for the "Believers", the global temperatures were no warmer than today, i.e., obviously, other factors besides atmospheric CO2 influence Earth's temperatures.

Plate 64- Earthquakes, seismic activities, tsunamis, natural events, landslides, hurricanes and tremors result from the earth's activities. They are natural geological events totally independent of human activity as is climate change. The progress of the Earth Sciences and the advancement of technologies associated with the understanding of our planet have led geologists to develop a new way of looking at the world and how it works - Plate Tectonics Theory. In fact, the Earth's rocky outer crust solidified billions of years ago, soon after it was formed, but this crust is not a solid envelope. It is broken up into huge, thick plates that drift atop the soft, underlying mantle. The plates are made of rock and drift all over the globe. They move both horizontally and vertically over long periods of time. They also change in size as their margins are added to, crushed together, or pushed back into the Earth's mantle. These plates, which have a thickness ranging from 80 to 400 km, are moving at a speed estimated at 1 to 10 cm per year. Most of the Earth's seismic activity (volcanoes and earthquakes) occurs at the plate boundaries as they interact and man cannot do anything about it, as is also the case probably with climate change and the global earth's temperature.

Plate 65- Plate Tectonics Theory, which so far has not yet been refuted, is a fascinating story of the Earth’s dynamic: (i) Continents drifting majestically from place to place breaking apart, colliding, and grinding against each other; (ii) Terrestrial mountain ranges rising up like rumples in rugs being pushed together; (iii) Oceans opening and closing and undersea mountain chains girdling the planet like seams creating violent earthquakes and fiery volcanoes. This theory describes the intricate design of a complex, living planet in a state of dynamic flux. The key principles of this theory are quite easy. The division of the outer parts of the Earth's interior into lithosphere and asthenosphere is based on mechanical differences and in the ways that heat is transferred. The lithosphere is cooler and more rigid, while the asthenosphere is hotter and mechanically weaker. The lithosphere loses heat by conduction whereas the asthenosphere transfers heat by convection and has a nearly adiabatic temperature gradient. This division should not be confused with the chemical subdivision of the Earth into core, mantle, and crust. The lithosphere contains both crust and some mantle. A given piece of mantle may be part of the lithosphere or the asthenosphere at different times, depending on its temperature, pressure and shear strength. The lithosphere exists as separate and distinct tectonic plates, which ride on the fluid-like asthenosphere. Plate motions range up to a typical 10-40 mm/a to about 160 mm/a. The plates consist of lithospheric mantle overlain by either of two types of crustal material: (a) oceanic crust and (b) continental crust. The two types of crust differ in thickness, with continental crust considerably thicker than oceanic (50 km vs 5 km). One plate meets another along a plate boundary, and plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features like mountains, volcanoes and oceanic trenches. Tectonic plates can include continental crust or oceanic crust, and a single plate typically carries both. The distinction between continental crust and oceanic crust is based on the density of constituent materials; oceanic crust is denser than continental crust owing to their different proportions of various elements, particularly silicon. Oceanic crust is denser because it has less silicon and heavier elements ("mafic") than continental crust ("felsic"). As a result, oceanic crust generally lies below sea level, while the continental crust projects above sea level.

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