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Universidade Fernando Pessoa

Porto, Portugal

Plate 13- One hundred fifty thousands year ago (150 ka), man had stone axes and he is really pleased for having domesticated fire. The global temperature varied with time between deep ice ages and interglacial periods. The total amplitude of the fluctuations, from the coldest to the warmest, is ± 5° C. After the end of the last ice age, man has bows and arrows, domesticated animals, agriculture, sedentary life, cities, exponential population growth and the Industrial Revolution (see next plate). In the plate above, at the end of the solid line, i.e., presently, the dashed lines show some projections of what are included because of greenhouse warming. These projections are just numerical simulations and contrary to what Arnold Schwartzenegeger (Governor of California) thinks, the debate (between "Alarmists" and "Sceptics) is not over (as every body knows M. Schwartzenegger is not a specialist in numeric simulation on computers, but in bodybuilding). “Alarmists” completely forget about the uncertainties of the numerical simulations by computer, which can predict the same thing with parameters and equations totally different. One must keep in mind, the great sensibility of computer climate models to the positive or negative feedbacks of Earth to the temperature variations. By the same token, one should not forget that the IPCC computer forecasts do not prove that greenhouse effect is a good explanation and it is absolutely not proven by the IPCC forecasts (http://www.pensee-unique.fr/theses.html). In 2007, to evaluate the contamination of the measured temperatures, R. Mckitrich and P. Michaels (Quantifying the influence of anthropogenic surface processes and inhomogeneities on gridded global climate data, J. Geophys. Res., 112) took into account the standard of living and a certain number of socioeconomic factors (including the competence of the observers) of the countries where the measuring stations are located. They found variations up to +0.7° C (mainly in south hemisphere) between the measured temperatures and the correct values.

Plate 14- Dendrochronology (tree-ring) dating is the method of scientific dating based on the analysis of tree-ring growth patterns. Astonishingly, this technique was developed during the first half of the 20th century originally by an astronomer working at the University of Arizona (A.E. Douglass) to better understand the influence of the solar activity (sunspot cycles) over the Earth’s climate patterns. The technique of dendrochronology can date the tree rings in many types of wood to the exact calendar year each ring was formed. The tree rings or annual rings can be seen in a horizontal cross-section cut through the trunk of a tree. They are the result of new growth in the vascular cambium (a cellular plant tissue from which phloem, xylem, or cork grows by division) and are synonymous with secondary growth. Visible rings result from the change in growth speed through the seasons of the year. One ring usually marks the passage of one year in the life of the tree. The rings are more visible in temperate zones, where the seasons differ more markedly. The inner portion of a growth ring is formed early in the growing season, when growth is comparatively rapid (hence the wood is less dense) and is known as "early wood". The outer portion is the "late wood" and is denser. "Early wood" is used in preference to "spring wood", as the latter term may not correspond to that time of year in climates where early wood is formed in the early summer (e.g. Canada) or in autumn, as in some Mediterranean species. Scientists have observed a relationship between local temperature and deuterium concentration in ice collected during periods that temperature was also known. There is no reason to believe that this relationship has changed over time, so the levels of deuterium in ancient ice can be used to reconstruct past climate. Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in oceans of approximately one atom in 6500 of hydrogen, ± 155 ppm.

Plate 15- Caption 16- Ice in glaciers has an increased proportional abundance of heavy oxygen (∂O18) if it was deposited during relatively warm periods. To understand why this might be so, we need to think about the process of glacier formation. The water-ice in glaciers originally came from the oceans as vapour, later falling as snow and becoming compacted in ice. When water evaporates, the heavy water (H2O18) is left behind and the water vapour is enriched in light water (H2O16). This is simply because it is harder for the heavier molecules to overcome the barriers to evaporation. Thus, glaciers are relatively enhanced in O16, while the oceans are relatively enriched in O18. This imbalance is more marked for colder climates than for warmer climates. In fact, it has been shown that a decrease of one part per million O18 in ice reflects a 1.5°C drop in air temperature at the time it originally evaporated from the oceans. While there are complexities with the analysis, a simple measurement of the isotopic ratio of O18 in ice cores can be directly related to climate. Ice cores from Greenland are layered, and the layers can be counted to determine age. The ∂O18 ratio can then be used as a thermometer of old climate. Other temperature indicators are: (I) pollen, (ii) faunal and floral remains, (iii) sediment types or composition and geomorphological features. In the ocean, indicators such as microplankton, pollen, and sediments settle to the sea floor, where they accumulate to provide a nearly continuous record of climate for millions of years. The limitations of paleo-climate reconstitutions result from uncertainties associated with dating the proxy indicators or other evidence. There are two fundamental types of dating: (a) Absolute dating, using techniques that identify the actual geological time represented by the evidence, however they are limited and rely predominately on evaluating the amount of decay of naturally occurring radioactive isotopes; (b) Relative dating, using techniques that are able to differentiate time relative to other points in time. Stratigraphy establishes a relative sequence of geological events within which the evidence lies. If this same geological sequence can be identified in multiple locations it can be used to establish the relationship between locations and the relative timing of the indicators (http://www.globalchange.umich.edu/globalchange1/current/lectures/samson/ paleoclimate/index.html).

Plate 16- The amount of CO2 emitted by humans breathing was calculate by Roper, L. D. (http://www.arts.bev.n/roperldavid/). Each day, the average person breathes in about 15, 000 litters, or approximately 35 pounds of air. Since air is 21% oxygen (molecular weight 16) and 78% nitrogen (molecular weight 14) by volume, oxygen is 23.5% by weight and nitrogen is 76.5% by weight, in air. So the amount of oxygen breathed in per day by the average person is about 35 x 0.235 = 8.2 lbs. Humans breath out about 16% oxygen by volume, so about 5% of the air by volume is converted to CO2, which is about (5/21) x 8.2 = ± 2 lbs of CO2 every day. The molecular weight of O2 is 32 and the molecular weight of CO2 is 12+32 = 44. Therefore, humans emit 44 x 2 x /32 lbs = ± 2.8 lbs of CO2 breathed out every day or about 1005 lbs = ± 0.5 tons per person per year. In 2005, Earth population was about 6.66 G. So the emitted CO2 per year by their breathing was about 3.3 x Gt. Most of that is due to the using of fossil carbon compounds to farm (fuel and fertilizer). The fraction of fossil carbon compounds used to burn for energy in agricultural infrastructure can already be accounted for in the atmospheric CO2 by calculation from fossil fuel extraction. In 2002, CO2 emissions due to human activities were about 27.6 Gt. Breathing comprises about 3.3 Gt of that amount, or about 12% of it. It may be not all of the human breathing is accounted for in "emissions due to human activities"; some of the fossil fuel used to make food available may not be counted. Globally, annual average emissions of carbon dioxide per capita due to human activities (other than breathing) have been fairly stable since 1990. For 2002, this figure was up to 3.93 t from 3.85 t in 2001. Per capita CO2 emissions for 2002 is 3.93 t/. Breathing adds about 12% more (0.5 t per person per year). If one day, the “Alarmist” conjecture that global warming is anthropogenic is corroborated, such a calculation suggest global warming is mainly a population-explosion problem. However, one should not forget that correlation does not mean necessarily causation.

Plate 17- Correlation does not imply causation is a phrase used in sciences and statistics to emphasize that correlation between two variables does not imply that one causes the other. Its negation, correlation proves causation, is a logical fallacy by which two events that occur together are claimed to have a cause-and-effect relationship. The fallacy is also known as cum hoc ergo propter hoc (means "with this, therefore because of this") and false cause. By contrast, the fallacy post hoc ergo propter hoc requires that one event occurs before the other and so may be considered a type of cum hoc (http://en.wikipedia.org/wiki). The cum hoc ergo propter hoc logical fallacy can be expressed as follows: A occurs in correlation with B, therefore, A causes B. In this type of logical fallacy, one makes a premature conclusion about causality after observing only a correlation between two or more factors. Generally, if one factor (A) is observed to only be correlated with another factor (B), it is sometimes taken for granted that A is causing B even when no evidence supports this. This is a logical fallacy because there are at least four other possibilities: (i) B may be the cause of A; (ii) some unknown third factor is actually the cause of the relationship between A and B; (iii) the "relationship" is so complex it can be labelled coincidental (i.e., two events occurring at the same time that have no simple relationship to each other besides the fact that they are occurring at the same time) and (iv) B may be the cause of A at the same time as A is the cause of B (contradicting that the only relationship between A and B is that A causes B). This describes a self-reinforcing system. In other words, there can be no conclusion made regarding the existence or the direction of a cause and effect relationship only from the fact that A and B are correlated. Determining whether there is an actual cause and effect relationship requires further investigation, even when the relationship between A and B is statistically significant, a large effect size is observed, or a large part of the variance is explained. This is particularly true when Al Gore in its "The Inconvenient Truth" (Paramount Pictures, 2006) showed a correlation between the carbon dioxide and temperatures curves and concluded that the increasing of CO2 is the responsible of the increasing of temperatures.

Plate 18- Caption 19- Climate changes can be considered in different time scales: (i) The long term (100's My); (ii) Medium term (1 My); (iii) Short term (160 ky) and (iv) Modern period (last few centuries). Superimposed on the long-term evolution, between hot and cold climates, have been many short-term fluctuations in climate similar to, and sometimes more severe than the varying glacial and interglacial states of the present ice age. Some of the most severe fluctuations, such as the Paleocene-Eocene Thermal Maximum, may be related to rapid increases in atmospheric CO2 due to the collapse of natural CH4 reservoirs in the oceans (methane clathrates). Severe climate changes also seem to have occurred during the course of the (a) Cretaceous-Tertiary; (b) Permian-Triassic; (c) Devonian and (d) Ordovician-Silurian extinction events. However, it is unclear to what degree these changes caused the extinctions rather than merely responding to other processes that may have been more directly responsible for the extinctions. Scientists advance that 60% of the animal and vegetal species disappeared during Ordovician-Silurian extension. The same happened during Devonian extinction. During the Permian-Triassic extinction, they think that 90% of the species living on land and in the oceans have disappeared during the Permian and about 20% during Triassic. During the last extinction (Cretaceous-Tertiary), two thirds of the earth’s population (animals and plants) disappeared leaving the place to mammals and then to man. Although the basic causes of climate changes are still not fully understood, many clues have been collected. Possible causes include: (1) Changes in solar output; (2) Changes in Earth's orbit; (3) Changes in the distribution of continents; (4) Changes in the concentration of Greenhouse Gases in the atmosphere, an others.

Plate 19- The relationships between long-term sea level changes, climate, volcanism and biotic crises have been quite well established by A. Fischer, in 1981 (Climatic oscillations in the biosphere. In: Nitecki M. H. (ed) Biotic crises in ecological and evolutionary time. Academic Press, New York, p. 102-131), as depicted above. This plate also strongly suggests that Stratigraphy is systemic, i.e., it cannot be studied in isolation. In fact, it is interconnected and interrelated with all Earth and Cosmic events. When sea level is high, volcanic activity is significant, climate is relatively warm and biotic crises reduce. At large scale, Precambrian and Cambrian were cold periods with development of ice sheets. The time-interval between Ordovician and Carboniferous was relatively hot, in spite of the ice sheets developed during Ordovician-Lower Silurian. During a large part of the Mesozoic, the temperature was relatively high, particularly during Jurassic and Cretaceous (no ice-sheets). During Late-Cenozoic the temperature was cold and ice sheets were relatively abundant. Biotic crises (Cutbill, J. L. and Funnell, B. M. 1967. Numerical analysis of The Fossil Record, in The fossil record, Geological Society of London, London, pp. 791-820 and Newell, N. D. 1963. Crises in the history of life, Scientific American, 208, 76-92) during which a high percentage of terrestrial and aquatic species disappeared, seems to have occurred mainly during the cold periods (Cambrian-Ordovician, Silurian, Carboniferous-Devonian, Permian, Triassic, Late-Cretaceous and Middle Cenozoic). In other words, climate changes are natural. They occur since the onset of geological history, which contradicts the “Alarmist” dogma. Thus, assuming that climate was stable before the industrial revolution is a fallacy, i.e., a conjecture based in unsound arguments.

Plate 20- Here, each bed, in overhang, is a turbidite, i.e., sediments transported by gravity (or turbidity) current and deposited in deeper part of the basin (toe of the continental slopes). Between them, the beds in withdrawal are shales resulting from a suspension sedimentation. Temporally, the turbiditic levels (sandstones) represent instantaneous deposits, while the inter-bedded shales represent time periods of hundreds or even thousands years. Each change of facies (lithology) corresponds to a climate change. In spite of the fact that some turbiditic currents are developed in highstand geologic conditions by instabilities of the shelf break, the large majority of them are induced by significant relative sea level falls created by the combined action of eustacy and subsidence. The eustatic variations are generated by sea-floor spreading (plate tectonics) or ice-sheet evolution (glaciology). Actually, during the development of ice-sheets, sea level (eustacy) falls and it rises when ice sheets melt. Climate changes are also quite important in non-marine sedimentation, particularly in river systems. Climate controls the rate of sediment delivery and long-term transfer of sediments to floodplain storage. The rate of sediment supply from erosional catchment to depositional basin, which varies in time and space, depends primarily upon: (i) Climate; (ii) Relief; (iii) Catchment slope and (iv) Lithology. Time variations in relative sediment supply are complex and vary widely according to the direction and magnitude of climate change. A nice example of interaction between climate and sedimentation was found in Cumaya Valley (California, USA) by DeLong, S. B. et al., 2007 (Late Quaternary alluviation and offset along the eastern Big Pine fault, southern California, Elsevier B.V.): “Sedimentation was probably a result of increased precipitation that caused saturation landsliding in steep catchments. It is possible that increased precipitation during the Last Glacial Maximum was caused by both continental-scale circulation pattern reorganization and increased Pacific storm frequency and intensity caused by early warming of nearby Pacific Ocean surface waters”.

Plate 21- As depicted on this plate, sea level changes occurred after the breakup of the supercontinent Proto-Pangea (or Rodhinia). Two 1st order eustatic cycles are quite obvious. As suggested by the drifting (dispersion and gathering) of the continents (on the right), sea level changes are clearly related with the plate tectonic activity. The Paleozoic eustatic high, with a sea level probably 200-250 m higher than today, took place around 500 Ma, when the dispersion of Paleozoic continents was maximal. Similarly, ± 91.5 Ma (means 91.5 millions years ago), the Meso-Cenozoic eustatic high corresponded to the maximal dispersion of the post-Pangea continents. On the contrary, sea level was low during the Pangea and Proto-Pangea supercontinents. These sea level variations were generated by volume variations of the oceanic basins created by volume changes of the oceanic ridges and not by climate changes. However, as illustrated on the next plate, 2nd and chiefly 3rd and higher order eustatic cycles are strongly dependent on climate change. In fact, glaciations (processes by which Earth’s areas are covered by glaciers or ice sheets) and deglaciations (the disappearance of ice from a previously glaciated region) created significant sea level variations and changes in the space available for the sediments (accommodation). When the space available for the sediments decreases there is not sedimentation (but for the majority of the turbidites) and erosion occurs quite often. On the other hand, an increase in accommodation induces sedimentation. Besides eustacy (global sea level variations measured in relation to the center of the Earth), there are other important parameters controlling sedimentation: (i) Subsidence; (ii) Uplift; (iii) Isostasy and (iv) Climate. Actually, the space available for the sediments (relative sea level change) is the result of the combined action of the eustacy and tectonics (subsidence, uplift, isostasy, etc.). The maximum amplitude of the eustacy was reached at the Cambrian (Phanerozoic 1st order eustatic cycle) and at Cenomanian-Turonian (Phanerozoic 2nd order eustatic cycle) and it seem to be 200 and 250 m higher than today.

Plate 22- Five orders of eustatic cycles have been identified in the geological record. They have been designated from 1st to 5th order cycles. The 1st order eustatic cycle corresponds to continental flooding cycles defined on the basis of major times of encroachment (landward extension) and restriction of sediments onto the cratons. They are associated with the break-up of supercontinents. They are recognized on all continents and are believed to be global. Their time duration is greater than 50 My, which P. Vail takes as the minimum duration for a 1st order cycle. Since the Phanerozoic, two eustatic cycles of 1st order have been recognized in the rock record. P. Vail (1977) considered that the youngest Phanerozoic 1st order eustatic cycle started at the base of the Triassic and extended to Present (more than 200 My). The older cycle started in the uppermost Proterozoic and extended to the end of Permian (more than 300 My). Eustatic cycles of 2nd to 4th order are believed to be caused by smaller magnitude, but higher frequency, and more rapid rates of eustatic change. They cause high frequency variations on the relative change of sea level curve (eustacy plus tectonics). In spite of the fact that the time duration of these cycles has changed since the birth of sequential stratigraphy, the majority of geologists assume the following time durations: (i) Higher than 50 My for 1st order eustatic cycles, (ii) Between 3-5 to 50 My for 2nd order eustatic cycles, (iii) Between 0.5 to 3-5 My for 3rd order eustatic cycles, (iv) Between 0.1 to 0.5 My for 4th and 5th order eustatic cycles. The classification of eustatic cycles in five orders clearly illustrate that P. Vail and coauthors considered eustacy as a multi-leveled complex geological event, in which each eustatic cycle forms a whole with respect to its parts, while, at same time, it is a part of a larger whole. In conclusion, seal level variations are natural geological events occurring since oceans were formed. They can be global or local and have different orders according their time duration and amplitude. Relative sea level changes (eustacy + tectonic influence) can be quite important (tectonics being the major factor). However, sea level variations (eustacy without tectonic influence) seldom reach greater than 100 m of amplitude.

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