Effects of Exercise on Muscular System

Effects of Exercise on Muscular System Smooth muscle tissue, such as skeletal and cardiac muscle tissue, can undergo hypertrophy the increase in the volume of tissue due to the enlargement of its component cells. Smooth muscle fibres are usually involuntary i.e. not under conscious control, and they are nonstriated meaning smooth. In addition, certain smooth muscle fibres retain a capacity for division and can grow by a process known as hyperplasia, like those in the uterus of women. Cardiac Cardiac muscle tissue forms the bulk of the wall of the heart. Like skeletal muscle tissue, it is striated (the muscle fibers contain alternating light and dark bands (striations) that are perpendicular to the long axes of the fibers). Unlike skeletal muscle tissue, its contraction is usually not under conscious control (involuntary). Skeletal Skeletal muscle tissue is named for its location attached to bones. It is striated; that is, the fibers (cells) contain alternating light and dark bands (striations) that are perpendicular to the long axes of the fibers. Skeletal muscle tissue can be made to contract or relax by conscious control (voluntary). All skeletal muscle fibres are not alike in structure or function. For example, skeletal muscle fibres vary in colour depending on their content of myoglobin (myoglobin stores oxygen until needed by the mitochondria). Skeletal muscle fibres contract with different velocities, depending on their ability to split Adenosine Triphosphate (ATP). Faster contracting fibres have greater ability to split ATP. In addition, skeletal muscle fibres vary with respect to the metabolic processes they use to generate ATP. They also differ in terms of the onset of fatigue. Based on various structural and functional characteristics, skeletal muscle fibres are classified into three types: Type I fibres, Type II B fibres and type II A fibres The different types of muscle fibres types of sports each is associated with Type I Fibres These fibres, also called slow twitch or slow oxidative fibres, contain large amounts of myoglobin, many mitochondria and many blood capillaries. Type I fibres are red, split ATP at a slow rate, have a slow contraction velocity, very resistant to fatigue and have a high capacity to generate ATP by oxidative metabolic processes. Such fibres are found in large numbers in the postural muscles of the neck. A sporting example of this could be a prop forward involved in a scrum in rugby. Type II A Fibres These fibres, also called fast twitch or fast oxidative fibres, contain very large amounts of myoglobin, very many mitochondria and very many blood capillaries. Type II A fibres are red, have a very high capacity for generating ATP by oxidative metabolic processes, split ATP at a very rapid rate, have a fast contraction velocity and are resistant to fatigue. Such fibres are infrequently found in humans. A sporting example of this is a sprinter such as Usain Bolt or a hurdler such as Colin Jackson. Type II B Fibres These fibres, also called fast twitch or fast glycolytic fibres, contain a low content of myoglobin, relatively few mitochondria, relatively few blood capillaries and large amounts glycogen. Type II B fibres are white, geared to generate ATP by anaerobic metabolic processes, not able to supply skeletal muscle fibres continuously with sufficient ATP, fatigue easily, split ATP at a fast rate and have a fast contraction velocity. Such fibres are found in large numbers in the muscles of the arms. A sporting example could be an Olympic weightlifter. How muscles produce movement in antagonistic pairs and the role of fixators and synergists There are up to four functional groups of muscles acting on joints. 1. Agonist: actively contract to make a movement. Muscle length reduces. 2. Antagonist: resists the muscle on opposite side, thereby controls the speed of the agonist muscle contraction. Thats why they say both agonist and antagonist muscles are working in pairs. Furthermore when the movement is reversed the original agonist becomes the antagonist and the original antagonist becomes the agonist. 3. Stabilisers: some muscles will hold the joint area stable while other three types of muscles are making a movement. 4. Modifiers: some muscles can slightly change the direction of force exerted by agonists dynamically Different types of muscle contractions Muscle Contractions can be divided into: Isotonic All lifting exercises require isotonic contractions. This happens when the muscle shortens as it contracts. An example of isotonic contraction can be seen when we flex the bicep muscle. Stand with one arm straight and the palm of the hand facing up. Roughly measure the length from the start of the biceps muscle to the point where it meets the shoulder. Now curl the hand towards the shoulder, the biceps muscle shortens as it contracts. When you reach the end point take another rough measurement of the biceps again, it will be much shorter. Another example is the triceps muscle (opposite of biceps). Do the same experiments again this time measure the triceps and start at the curled position. The triceps shortens as the arm straightens. Other examples are lifting objects above the head front shoulder (anterior deltoid) shortens lifting object up from lying position chest muscle shortens lifting body up from squat position quadriceps muscle shortens as legs extend doing a sit up throwing a ball swinging a bat Eccentric Eccentric contraction is the opposite of isotonic; the muscle lengthens as it gains tension. These are much less common and not as beneficial as the common Isotonic. An example is when someone manages to pull your arm straight while at the same time you are try to keep the arm locked in one position. In other words, the load is too great! Other examples are running downhill walking downstairs landing on the ground from a jump Isometric An Isometric contraction occurs when there is tension on a muscle but no movement is made causing the length of the muscle to remain the same. This type of contraction is also referred to as a static contraction. Some bodybuilders make up their own exercises using Isometric contraction in order to develop strength; an example is when someone attempts to curl one arm upwards but is held by using equal resistance from the other arm. attempting to lift an immoveable object holding a weight at arms length some wrestling movements Isokinetic Similar to the isotonic contraction, the Isokinetic contraction causes the muscle to shorten as it gains tension. The difference is Isokinetic requires a constant speed over the entire range of motion, therefore this type of contraction require special equipment to exercise properly. An example is an arm stroke when swimming, the even resistance from the water offers a constant speed at maximal contractions. Sliding Filament Theory The sliding filament theory is the basic summary of the process of skeletal muscle contraction. Myosin moves along the filament by repeating a binding and releasing sequence that causes the thick filament to move over the thinner filament. This progresses in sequential stages. By progressing through this sequence the filaments slide and the skeletal muscles contract and release. First Stage: The first stage is when the impulse gets to the unit. The impulse travels along the axon and enters the muscle through the neuromuscular junction. This causes full two to regulate and calcium channels in the axon membrane to then open. Calcium ions come from extra cellular fluid and move into the axon terminal causing synaptic vessels to fuse with pre synaptic membranes. This causes the release of acetylcholine (a substance that works as a transmitter) within the synaptic cleft. As acetylcholine is released it defuses across the gap and attaches itself to the receptors along the sarcolemma and spreads along and across the muscle fibre. Second Stage: The second stage is for the impulse spreads along the sarcolemma. The action potential spreads quickly along the sarcolemma once it has been generated. This action continues to move deep inside the muscle fibre down to the T tubules and the action potential triggers the release of calcium ions from the sarcoplasmic reticulum. Third Stage: During the third stage calcium is released from the sarcoplasmic reticulum and actin sites are activated. Calcium ions once released begin binding to Troponin. Tropomyosin blocking the binding of actin is what causes the chain of events that lead to muscle contraction. As calcium ions bind to the Troponin it changes shape which removes the blocking action of Tropomyosin (thin strands of protein that are wrapped around the actin filaments). Actin active sites are then exposed and allow myosin heads to attach to the site. Fourth Stage: The fourth stage then begins in which myosin heads attach to actin and form cross bridges, ATP is also broken down during this stage. Myosin binds at this point to the exposed binding sites and through the sliding filament mechanism the muscles contract. Fifth Stage: During the fifth stage the myosin head pulls the Actin filament and ADP and inorganic Phosphates are released. ATP binding allows the myosin to detach and ATP hydrolysis occurs during this time. This recharges the myosin head and then the series starts over again. Stage Six: Cross bridges detach while new ATP molecules are attaching to the myosin head while the myosin head is in the low-energy configuration. Cross bridge detachment occurs while new ATP attaches itself to the myosin head. New ATP attaches itself to the myosin head during this process. Stage Seven: During stage seven the ATP is broken down and used as energy for the other areas including new cross bridge formation. Then the final stage (stage 8) begins and a drop in stimulus causes the calcium concentrate and this decreases the muscle relaxation. Below is an example of how sliding filament theory works How the muscular system responds to exercise How muscles work Muscles fall in to two types: Voluntary and involuntary. Brain stimulation through a signal to voluntary muscles makes them work to do a task like pulling. There is no brain stimulation for involuntary muscles. When people exercise their voluntary muscles, they more efficiently they function. When functioning efficiently, it is easier for people to do their work. Muscles will function with greater efficiency and ease when they have regular exercise. This is known as the first lesson of exercise Muscular exercise and the affects of exercise on the muscles Inside the muscles nerves relay messages to and from the brain. Food is bought to the muscles by blood vessels which do the work that the brain has ordered. When muscles are exercised, they convert a substance known as glucose into energy. During exercise, heat is produced and carbon dioxide is given off as a waste product. Short term effects: When we begin to exercise the body has to respond to the change in activity level in order to maintain a constant internal environment (homeostasis). Here are the changes which must take place to the muscles so that the exercise can be performed: The higher rate of muscle contraction depletes energy stores and so stimulates a higher rate of energy metabolism. The bodys energy stores are slowly depleted Myoglobin releases its stored oxygen to use in aerobic respiration. O2 can now be diffused into the muscle from the capillaries more quickly due to the decreased O2 concentration in the muscle. Long term effects: Increased numbers of mitochondria (the cells powerhouse) means an increase in the rate of energy production. The muscles, bones and ligaments become stronger to cope with the additional stresses and impact put through them. with the additional stresses and impact put through them. The amount of myoglobin within skeletal muscle increases, which allows more Oxygen to be stored within the muscle, and transported to the mitochondria. Muscles are capable of storing a larger amount of glycogen for energy. Enzymes involved in energy production become more concentrated and efficient to aid the speed of metabolism. Benefits of exercise Muscles are working hard during exercise, which is good for them. The harder they are worked over time, the more they can do. Muscles must have the proper intake of food (in the shape of protein, complex carbohydrates and fats) along with sufficient water to achieve the maximum amount of work possible. Contraction of a muscle makes it a more efficient tool. Contraction with resistance aids the muscle growth and increases its capacity for future demands. Multiple contractions through exercise brings about the greatest efficiencies.

Are Humans Responsible for Global Warming?

Are Humans Responsible for Global Warming? A REVIEW OF THE FACTS APRIL 2007 AUTHORS James Wang, Ph. D. Bill Chameides, Ph. D. Are Humans Responsible for Global Warming? The case for attributing the recent global warming to human activities rests on the following undisputed scientific facts: †¢ Carbon dioxide (CO2) is a greenhouse gas that warms the atmosphere. †¢ Since pre-industrial times, atmospheric CO2 concentrations have increased from about 280 parts per million (ppm) to over 380 ppm.Current concentrations of CO2 and other greenhouse gases are unprecedented in at least the last 650,000 years, based on records from gas bubbles trapped in polar ice. †¢ Independent measurements demonstrate that the increased CO2 in the atmosphere comes from burning fossil fuels and forests. The isotopic composition of carbon from these sources contains a unique â€Å"fingerprint. † †¢ Since pre-industrial times, global average temperatures have increased by about 0. 7? C , with about half of the warming occurring over the past few decades. The only quantitative and internally consistent explanation for the recent global warming includes the intensified greenhouse effect caused by the increase in CO2 and other greenhouse gases. The U. S. National Academy of Sciences—the independent organization of the country’s most renowned scientists established by Congress to advise the nation on scientific and technical issues—has concluded: â€Å"The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action. Some argue that the recent global warming is due to natural fluctuations and not to human activities. This argument and its fallacies are discussed below. Argument 1: CO2 is not coming from human activities CO2 has natural sources: volcanoes for example. All animals exhale it. How can human activities be affecting the concentration of CO2 on a global scale? The Facts Natural processes e mit large quantities of CO2 into the atmosphere, but they also remove it—at nearly identical rates.This balance maintained the concentration of CO2 at a stable level for thousands of years prior to the Industrial Revolution. In the case of global warming, the question is: What is causing the increase in CO2 concentrations? The answer turns out to be incontrovertible. The isotopic composition of carbon in atmospheric CO2 provides a unique â€Å"fingerprint† that tells scientists that the lion’s share of the additional CO2 accumulating in the atmosphere is from the burning of fossil fuels. Argument 2: No one really knows why the climate variesThe global climate has fluctuated considerably over the Earth’s history, either for unknown reasons or because of â€Å"internal variability† in the climate system. We do not know enough about the climate system to attribute the present global warming to any specific cause. The Facts It is true that the Earthâ⠂¬â„¢s climate has exhibited wide swings over geologic time due to natural processes. However, scientists have reasonable qualitative explanations for most of the significant variations in 2 limate over geologic time;1 they can be largely attributed to specific processes, not to unknown internal oscillations. Many of the major climatic changes can be traced to changes in the Earth’s orbit around the sun (Hays et al. Science, 194, 1976, pg. 1121). Others can be linked to specific events (such as the impact of a comet or meteorite or the assembly or breakup of supercontinents) that led to large changes in the concentration of atmospheric greenhouse gases.For more recent times (the past millennium), scientists have been able to quantitatively attribute the major temperature fluctuations to changes in solar activity, volcanic eruptions, and human-produced greenhouse gases and particulate pollution. These natural processes can not explain the current warming. Argument 3: The Medie val Warm Period disproves global warming The current warming trend is analogous to the Medieval Warming Period (MWP). Since the MWP was obviously a natural event, the current warming is also likely caused by natural processes. The FactsThe Medieval Warm Period (MWP) refers to a relatively warm period lasting from about the 10th to the 14th century. 2 However, the initial evidence for the MWP was largely based on data3 gathered from Europe, and more recent analyses indicate that the MWP was not a global phenomenon. A number of reconstructions of millennium-scale global temperatures have indicated that the maximum globally averaged temperature during the MWP was not as extreme as present-day temperatures and that the warming was regional rather than global. Perhaps the most well-known of these is that of Michael Mann and colleagues (Nature, 392, 1998, pg. 779).Their reconstruction produced the so-called â€Å"hockey stick† graphic that contributed to this conclusion in the 2001 assessment of the Intergovernmental Panel on Climate Change: â€Å"The†¦'Medieval Warm Period' appear(s) to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries. † The accuracy of the â€Å"hockey stick† graphic was widely discussed in the press when the Mann et al. methodology was criticized by McIntyre and McKitrick (Geophys. Res. Lettr, 32, 2005, pg. L03710). Less attention was given to subsequent studies, such as that of Moberg and colleagues (Nature, 433, 2005, pg. 13) and Osborn and Briffa (Science, 311, 2006, pg. 841) that were based on different, independent methodologies but reached conclusions similar to Mann. Observations of melting high altitude glaciers are perhaps even more telling. Andean glaciers that have been intact for more than 5,000 years are now rapidly melting (Thompson et al. Proc. Nat. Acad. Sci. , 103, 2006, pg. 10536). If the MWP was truly global, these glaciers would not have sur vived. More generally, it is a logical fallacy to argue that because the climate has changed in the past due to natural causes, the current warming trend must also be due to natural causes.The debate over the magnitude and causes of earlier climate change such as the MWP is of scientific interest, but it does not invalidate the considerable direct scientific evidence that human-produced greenhouse gases have been causing the Earth to warm recently. Argument 4: Recent predictions of a new ice age disprove global warming In the 1970s climate scientists were saying an ice age was imminent. Now they say the Earth is warming. They don’t know what they are talking about. The FactsThe Earth’s climate for the past 2 million years has been characterized by ice ages lasting close to 100,000 years, punctuated by relatively short (10,000- to 30,000-year) warm periods or â€Å"interglacials. † The swing from glacial to interglacial is caused by changes in the Earth’s orbit around the sun amplified by natural feedbacks involving greenhouse gases (Hays et al. Science, 194, 1976, pg. 1121). The Earth entered the present interglacial about 10,000 years ago. All things being equal (i. e. , in the absence of a large human-produced source of CO2) it is highly likely that the Earth will swing back into a glacial period or ice age.But this will not occur for thousands of years. 3 As early as the 19th century, scientists recognized that greenhouse gases warm the planet, and that increases in atmospheric carbon dioxide could lead to global warming on time scales of decades to centuries—much shorter than the fluctuations related to ice ages and interglacials. Around the same time, global temperatures began to increase and scientists became increasingly concerned that humans were interfering with the climate. In the 1950s the upward trend in global temperatures unexpectedly halted and temperatures declined somewhat.This led some scientists to become c oncerned about global cooling and, in turn, to headlines in the popular press about an imminent ice age. What the skeptics fail to admit is that within the scientific literature—as opposed to the popular press—global warming remained a serious concern. Many scientists of the time argued that whatever the cause of the cooling, natural or otherwise, it would be eventually overshadowed by the warming effect of carbon dioxide. In 1979, the National Academy of Sciences warned that a doubling of carbon dioxide would increase global temperatures by 1. 5 to 4. oC (Carbon Dioxide and Climate: A Scientific Assessment, NAS Press, 1979) and shortly thereafter a resumption of the upward trend in temperatures was detected. Over the past quarter century, scientific research on global climate change has intensified, and programs on an international scale have been organized. More and more data are included in computer models that are capable of recreating past trends and more precisel y predicting future scenarios. We now know that the mid-20th century pause in global warming was caused by pollution from burning coal, which produced tiny particles or aerosols that blocked the energy from the sun.As aerosol emissions were controlled but greenhouse gas pollution continued to increase, the cooling effect of the aerosols was overwhelmed by the greenhouse gases, and global warming resumed. Argument 5: Scientists cannot â€Å"prove† current warming is not natural Climate scientists can not prove that the current warming is not due to natural processes and therefore can not claim with certainty that the warming is due to human interference. The Facts It is of course true that, in a complex system like climate, it is virtually impossible to prove a negative; i. e. that natural processes are not causing the current warming. What we can do is eliminate every possible natural explanation that can be posited. Thermodynamics tells us that the warming of the Earthâ€⠄¢s lower atmosphere must arise from one or more processes that supply excess heat to the lower atmosphere. Besides the greenhouse effect, the viable processes are (1) increased output from the sun; (2) increased absorption of heat from the sun due to a change in the Earth’s planetary reflectivity or â€Å"albedo†; and (3) an internal variation in the climate system that transfers heat from one part of the Earth to the atmosphere.Direct observations confirm that none of these explains the observed warming over the latter half of the 20th century. For example there has been no appreciable change in solar output over the past two decades (see Figure 1). Figure 1. Change in solar output from 1980 to 2005. Figure 1 shows the relative change in solar output determined from two of satellite measurements over a two-decade period. The data show variability in solar output corresponding to the 11-year sunspot cycle, but no secular trend. Source: After Lean and Froelich, 2006. 4 Satellite data reveal that the Earth’s reflectivity increased (causing cooling instead of warming) in the ’60’s, ‘70s, and early ‘80s and has decreased modestly since. 4 The overall warming from the recent decrease in reflectivity is also small compared to the greenhouse warming. In the case of internal variations, the ocean is the only viable reservoir of internal heat that could have caused the atmosphere to warm on decadal time-scales. However, observations show that the heat content of the ocean has increased instead of decreased over the past few decades (See Figure 2).This indicates that the atmosphere has been a source of heat to the ocean rather than vice versa. Moreover, the amount of heat increase in the ocean is consistent with what is needed to balance the Earth’s energy budget given the excess heating from the enhanced greenhouse effect and the amount of excess heat observed to be stored in the atmosphere (Hansen et al. Science, 3 08, 2005, pg. 1431). In other words, the amount of heat stored in the ocean over recent years matches the amount of heat that models predict should be trapped on Earth due to the increase in greenhouse gases. Figure 2.Change in heat content of ocean 1955 to 2005 Source: After Levitus et al. 2005. FIGURE 2 SHOWS THE RELATIVE CHANGE IN THE HEAT COTENT OF THE OCEAN FROM 1955 TO 2005 BASED ON A COMPREHENSIVE ANALYSIS OF OCEAN TEMPERATURE MEASUREMENTS. THE DATA SHOW SHORT TERM VARIABILITY BUT A CLEAR UPWARD TREND ON DECADAL TIME-SCALES. Conclusion †¢ The Medieval Warm Period does not represent an analogy to the warming of the late 20th century, for which scientists have independent evidence of human causation, and the evidence strongly suggests that the MWP was a regional, rather than a global phenomenon. Our understanding of the climate system is sufficient to provide qualitative models for most global or hemispheric climatic variations over geologic history and quantitative models for variations over the past millennium. †¢ The Earth’s climate may return to ice age conditions in thousands of years, but this does not preclude devastating effects from global warming over the next few centuries. 5 †¢ All known natural explanations for the current global warming trend have been eliminated by direct observations.The human-intensified greenhouse effect provides the only quantitative explanation for the current warming trend. About the authors Dr. Wang received his doctorate from Harvard University and works as a climate scientist at Environmental Defense. He has published several peer-reviewed papers on the global methane budget and was the author of â€Å"The Latest Myths and Facts on Global Warming,† which was read into the congressional record by Senator John McCain in 2005. The report is available at http://www. undoit. org/pdfs/mythsvfacts. pdf. Dr. Chameides, chief scientist at Environmental Defense, is a member of the U.S. National A cademy of Sciences and has been named a National Associate of the National Academies. He is also an American Geophysical Union Fellow, and has received the American Geophysical Union's Macelwane Award. Dr. Chameides has served as editor of the Journal of Geophysical Research and is the author or coauthor of more than 120 scientific publications and five books. He received his doctorate from Yale University. The explanations are qualitative instead of quantitative because we do not have quantitative data from these events in the distant past to construct their exact histories. It has been suggested based on temperature reconstructions and model simulations that the MWP may have been caused by increased solar activity or a dearth of volcanic activity. 3 th Because worldwide temperature measurements do not exist before the 19 century, temperature records before th the 19 century are based on reconstructions of the temperature from the variations in temperature-sensitive proxies (e. g. , tree rings, isotopes in ice cores). 4 These variations are possibly due to changes in the concentrations of atmospheric aerosols produced from the burning of fossil fuels and biomass. 1 6 Are Humans Responsible for Global Warming? Are Humans Responsible for Global Warming? A REVIEW OF THE FACTS APRIL 2007 AUTHORS James Wang, Ph. D. Bill Chameides, Ph. D. Are Humans Responsible for Global Warming? The case for attributing the recent global warming to human activities rests on the following undisputed scientific facts: †¢ Carbon dioxide (CO2) is a greenhouse gas that warms the atmosphere. †¢ Since pre-industrial times, atmospheric CO2 concentrations have increased from about 280 parts per million (ppm) to over 380 ppm.Current concentrations of CO2 and other greenhouse gases are unprecedented in at least the last 650,000 years, based on records from gas bubbles trapped in polar ice. †¢ Independent measurements demonstrate that the increased CO2 in the atmosphere comes from burning fossil fuels and forests. The isotopic composition of carbon from these sources contains a unique â€Å"fingerprint. † †¢ Since pre-industrial times, global average temperatures have increased by about 0. 7? C , with about half of the warming occurring over the past few decades. The only quantitative and internally consistent explanation for the recent global warming includes the intensified greenhouse effect caused by the increase in CO2 and other greenhouse gases. The U. S. National Academy of Sciences—the independent organization of the country’s most renowned scientists established by Congress to advise the nation on scientific and technical issues—has concluded: â€Å"The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action. Some argue that the recent global warming is due to natural fluctuations and not to human activities. This argument and its fallacies are discussed below. Argument 1: CO2 is not coming from human activities CO2 has natural sources: volcanoes for example. All animals exhale it. How can human activities be affecting the concentration of CO2 on a global scale? The Facts Natural processes e mit large quantities of CO2 into the atmosphere, but they also remove it—at nearly identical rates.This balance maintained the concentration of CO2 at a stable level for thousands of years prior to the Industrial Revolution. In the case of global warming, the question is: What is causing the increase in CO2 concentrations? The answer turns out to be incontrovertible. The isotopic composition of carbon in atmospheric CO2 provides a unique â€Å"fingerprint† that tells scientists that the lion’s share of the additional CO2 accumulating in the atmosphere is from the burning of fossil fuels. Argument 2: No one really knows why the climate variesThe global climate has fluctuated considerably over the Earth’s history, either for unknown reasons or because of â€Å"internal variability† in the climate system. We do not know enough about the climate system to attribute the present global warming to any specific cause. The Facts It is true that the Earthâ⠂¬â„¢s climate has exhibited wide swings over geologic time due to natural processes. However, scientists have reasonable qualitative explanations for most of the significant variations in 2 limate over geologic time;1 they can be largely attributed to specific processes, not to unknown internal oscillations. Many of the major climatic changes can be traced to changes in the Earth’s orbit around the sun (Hays et al. Science, 194, 1976, pg. 1121). Others can be linked to specific events (such as the impact of a comet or meteorite or the assembly or breakup of supercontinents) that led to large changes in the concentration of atmospheric greenhouse gases.For more recent times (the past millennium), scientists have been able to quantitatively attribute the major temperature fluctuations to changes in solar activity, volcanic eruptions, and human-produced greenhouse gases and particulate pollution. These natural processes can not explain the current warming. Argument 3: The Medie val Warm Period disproves global warming The current warming trend is analogous to the Medieval Warming Period (MWP). Since the MWP was obviously a natural event, the current warming is also likely caused by natural processes. The FactsThe Medieval Warm Period (MWP) refers to a relatively warm period lasting from about the 10th to the 14th century. 2 However, the initial evidence for the MWP was largely based on data3 gathered from Europe, and more recent analyses indicate that the MWP was not a global phenomenon. A number of reconstructions of millennium-scale global temperatures have indicated that the maximum globally averaged temperature during the MWP was not as extreme as present-day temperatures and that the warming was regional rather than global. Perhaps the most well-known of these is that of Michael Mann and colleagues (Nature, 392, 1998, pg. 779).Their reconstruction produced the so-called â€Å"hockey stick† graphic that contributed to this conclusion in the 2001 assessment of the Intergovernmental Panel on Climate Change: â€Å"The†¦'Medieval Warm Period' appear(s) to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries. † The accuracy of the â€Å"hockey stick† graphic was widely discussed in the press when the Mann et al. methodology was criticized by McIntyre and McKitrick (Geophys. Res. Lettr, 32, 2005, pg. L03710). Less attention was given to subsequent studies, such as that of Moberg and colleagues (Nature, 433, 2005, pg. 13) and Osborn and Briffa (Science, 311, 2006, pg. 841) that were based on different, independent methodologies but reached conclusions similar to Mann. Observations of melting high altitude glaciers are perhaps even more telling. Andean glaciers that have been intact for more than 5,000 years are now rapidly melting (Thompson et al. Proc. Nat. Acad. Sci. , 103, 2006, pg. 10536). If the MWP was truly global, these glaciers would not have sur vived. More generally, it is a logical fallacy to argue that because the climate has changed in the past due to natural causes, the current warming trend must also be due to natural causes.The debate over the magnitude and causes of earlier climate change such as the MWP is of scientific interest, but it does not invalidate the considerable direct scientific evidence that human-produced greenhouse gases have been causing the Earth to warm recently. Argument 4: Recent predictions of a new ice age disprove global warming In the 1970s climate scientists were saying an ice age was imminent. Now they say the Earth is warming. They don’t know what they are talking about. The FactsThe Earth’s climate for the past 2 million years has been characterized by ice ages lasting close to 100,000 years, punctuated by relatively short (10,000- to 30,000-year) warm periods or â€Å"interglacials. † The swing from glacial to interglacial is caused by changes in the Earth’s orbit around the sun amplified by natural feedbacks involving greenhouse gases (Hays et al. Science, 194, 1976, pg. 1121). The Earth entered the present interglacial about 10,000 years ago. All things being equal (i. e. , in the absence of a large human-produced source of CO2) it is highly likely that the Earth will swing back into a glacial period or ice age.But this will not occur for thousands of years. 3 As early as the 19th century, scientists recognized that greenhouse gases warm the planet, and that increases in atmospheric carbon dioxide could lead to global warming on time scales of decades to centuries—much shorter than the fluctuations related to ice ages and interglacials. Around the same time, global temperatures began to increase and scientists became increasingly concerned that humans were interfering with the climate. In the 1950s the upward trend in global temperatures unexpectedly halted and temperatures declined somewhat.This led some scientists to become c oncerned about global cooling and, in turn, to headlines in the popular press about an imminent ice age. What the skeptics fail to admit is that within the scientific literature—as opposed to the popular press—global warming remained a serious concern. Many scientists of the time argued that whatever the cause of the cooling, natural or otherwise, it would be eventually overshadowed by the warming effect of carbon dioxide. In 1979, the National Academy of Sciences warned that a doubling of carbon dioxide would increase global temperatures by 1. 5 to 4. oC (Carbon Dioxide and Climate: A Scientific Assessment, NAS Press, 1979) and shortly thereafter a resumption of the upward trend in temperatures was detected. Over the past quarter century, scientific research on global climate change has intensified, and programs on an international scale have been organized. More and more data are included in computer models that are capable of recreating past trends and more precisel y predicting future scenarios. We now know that the mid-20th century pause in global warming was caused by pollution from burning coal, which produced tiny particles or aerosols that blocked the energy from the sun.As aerosol emissions were controlled but greenhouse gas pollution continued to increase, the cooling effect of the aerosols was overwhelmed by the greenhouse gases, and global warming resumed. Argument 5: Scientists cannot â€Å"prove† current warming is not natural Climate scientists can not prove that the current warming is not due to natural processes and therefore can not claim with certainty that the warming is due to human interference. The Facts It is of course true that, in a complex system like climate, it is virtually impossible to prove a negative; i. e. that natural processes are not causing the current warming. What we can do is eliminate every possible natural explanation that can be posited. Thermodynamics tells us that the warming of the Earthâ€⠄¢s lower atmosphere must arise from one or more processes that supply excess heat to the lower atmosphere. Besides the greenhouse effect, the viable processes are (1) increased output from the sun; (2) increased absorption of heat from the sun due to a change in the Earth’s planetary reflectivity or â€Å"albedo†; and (3) an internal variation in the climate system that transfers heat from one part of the Earth to the atmosphere.Direct observations confirm that none of these explains the observed warming over the latter half of the 20th century. For example there has been no appreciable change in solar output over the past two decades (see Figure 1). Figure 1. Change in solar output from 1980 to 2005. Figure 1 shows the relative change in solar output determined from two of satellite measurements over a two-decade period. The data show variability in solar output corresponding to the 11-year sunspot cycle, but no secular trend. Source: After Lean and Froelich, 2006. 4 Satellite data reveal that the Earth’s reflectivity increased (causing cooling instead of warming) in the ’60’s, ‘70s, and early ‘80s and has decreased modestly since. 4 The overall warming from the recent decrease in reflectivity is also small compared to the greenhouse warming. In the case of internal variations, the ocean is the only viable reservoir of internal heat that could have caused the atmosphere to warm on decadal time-scales. However, observations show that the heat content of the ocean has increased instead of decreased over the past few decades (See Figure 2).This indicates that the atmosphere has been a source of heat to the ocean rather than vice versa. Moreover, the amount of heat increase in the ocean is consistent with what is needed to balance the Earth’s energy budget given the excess heating from the enhanced greenhouse effect and the amount of excess heat observed to be stored in the atmosphere (Hansen et al. Science, 3 08, 2005, pg. 1431). In other words, the amount of heat stored in the ocean over recent years matches the amount of heat that models predict should be trapped on Earth due to the increase in greenhouse gases. Figure 2.Change in heat content of ocean 1955 to 2005 Source: After Levitus et al. 2005. FIGURE 2 SHOWS THE RELATIVE CHANGE IN THE HEAT COTENT OF THE OCEAN FROM 1955 TO 2005 BASED ON A COMPREHENSIVE ANALYSIS OF OCEAN TEMPERATURE MEASUREMENTS. THE DATA SHOW SHORT TERM VARIABILITY BUT A CLEAR UPWARD TREND ON DECADAL TIME-SCALES. Conclusion †¢ The Medieval Warm Period does not represent an analogy to the warming of the late 20th century, for which scientists have independent evidence of human causation, and the evidence strongly suggests that the MWP was a regional, rather than a global phenomenon. Our understanding of the climate system is sufficient to provide qualitative models for most global or hemispheric climatic variations over geologic history and quantitative models for variations over the past millennium. †¢ The Earth’s climate may return to ice age conditions in thousands of years, but this does not preclude devastating effects from global warming over the next few centuries. 5 †¢ All known natural explanations for the current global warming trend have been eliminated by direct observations.The human-intensified greenhouse effect provides the only quantitative explanation for the current warming trend. About the authors Dr. Wang received his doctorate from Harvard University and works as a climate scientist at Environmental Defense. He has published several peer-reviewed papers on the global methane budget and was the author of â€Å"The Latest Myths and Facts on Global Warming,† which was read into the congressional record by Senator John McCain in 2005. The report is available at http://www. undoit. org/pdfs/mythsvfacts. pdf. Dr. Chameides, chief scientist at Environmental Defense, is a member of the U.S. National A cademy of Sciences and has been named a National Associate of the National Academies. He is also an American Geophysical Union Fellow, and has received the American Geophysical Union's Macelwane Award. Dr. Chameides has served as editor of the Journal of Geophysical Research and is the author or coauthor of more than 120 scientific publications and five books. He received his doctorate from Yale University. The explanations are qualitative instead of quantitative because we do not have quantitative data from these events in the distant past to construct their exact histories. It has been suggested based on temperature reconstructions and model simulations that the MWP may have been caused by increased solar activity or a dearth of volcanic activity. 3 th Because worldwide temperature measurements do not exist before the 19 century, temperature records before th the 19 century are based on reconstructions of the temperature from the variations in temperature-sensitive proxies (e. g. , tree rings, isotopes in ice cores). 4 These variations are possibly due to changes in the concentrations of atmospheric aerosols produced from the burning of fossil fuels and biomass. 1 6

Up in Arms About Short Essay Topics for Interview?

Up in Arms About Short Essay Topics for Interview? Short Essay Topics for Interview - Dead or Alive? Which will be part of my next review for a different show. If you're in need of custom essay online, don't hesitate to get in touch with us now for we believe in providing result oriented and efficient classification essay assistance to our clients. If you would like a job, you've got to earn a case for yourself. If you're a student, or anyone else who's going to do lots of writing, then you ought to provide yourself with the most suitable technology, especially now, when it's virtually costless to achieve that. There are lots of people of the world who don't practice what they preach. There's no greater approach to do so than to write. You awaken and realize that you've had a sex change. Go over it a couple more times to be sure you're happy with your work. If you're a student, you should attempt to master the quick essay. An essay is a fairly short bit of writing on a specific topic. This essay will end up being 300 to 600 words, so in the event that you pick solid examples and make certain you are very clear in your explanations of things, it won't really hard to reach. On the flip side, in the event the brief essay is viewed as an important learning tool, it's not hard to realize how it can benefit students. When it is argumentative or informative essays, you must develop a topic that could grab the interest of the reader very quickly and this isn't such an easy job. Sociology essays handle the study of human social behavior in a society, therefore, it is quite interesting for the students who want to know more about human psyche but boring for people who don't like studying their species. Selecting the topic is crucial, particularly for a 2-minute speech and will aid with student progress. Following are a few of the suggested sociology essay topic for those students that are unable to choose a great topic for their assignment. Life, Death, and Short Essay Topics for Interview Therefore, if you learn how to think, through writing, then you'll develop a well-organized, efficient mind and one which is well-founded and certain. Write the introduction you can Now sit down to begin writing your essay. For thoughts and tips to help you begin writing a brief story of your own, continue r eading. Lots of the creative writing prompts I've written on this website might be used for a brief story. It's a convention of the brief story genre, and once you begin to look for it, you will see it everywhere. The greatest short story idea on the planet won't help you in the event that you don't write this, and a mediocre idea can be created into an award winning story if it's written well. You're the only person who really can compose the story. A quick story is tight there is not any room for extended exposition, there are not any subplots to explore, and by the close of the story there ought to be no loose ends to tie up. The Birth of Short Essay Topics for Interview When the brief essay is employed as a building block of composition skills, it is quite valuable. Don't forget that editing is a collaborative approach. Don't pitch an investigative piece in case you don't understand how to commence reporting it. Determine what you like, and you will be on the path to great writing topics. Now the question is the way to develop into sincere if you previously believe you're si ncere. An expert in a given subject area loses their capacity to use that skill any longer. It's advisable that you just select the topic that you're able to deal with, for instance, if you're not t sketching the personality characteristics then you ought to better not elect for it. The issue with the brief essay is as soon as an instructor relies on it as the sole way of expression in a class. Facts, Fiction and Short Essay Topics for Interview So when you're writing an essay, you're harnessing the complete might of culture to your life. Brainstorming ideas Your essay should be unique. Write a Testimonial Few very good words, go a ways, thanks! An essay is, thus, a quick piece written by somebody trying to explore a topic or answer a question. You might even are looking for a specialist on the topic matter and conduct an interview. Topics for young children ought to be fun, easy, and something they are easily able to come up with on their own. The very first part, wher e the examiner takes your interview, is quite a light personal conversation. Start asking your own questions regarding your topic, then answer them. If even 1 word looks extraneous, it must go. If you refuse to get tempted for fifteen minutes (25 on a really lousy day) you will realize that the clamor in your head will settle down and you're going to be in a position to focus on writing. A better part of the moment, writers find it hard to answer that question. The absolute most helpful writers write each and every day, at the very least a bit. The Lost Secret of Short Essay Topics for Interview A 2-minute speech is a huge method to ease into public speaking and that's why it's commonly utilized in the classroom. You don't want to provide them a topic that's too difficult or requires an excessive amount of preparation. When you prepare for the Reading section, it's better for you whether you read an excessive amount of context in English. In the speaking section, you have to be confident of what you speak. Top Short Essay Topics for Interview Choices You will be pleased to know that it has best deals like gift vouchers etc. and should you shop above thousand then you will receive totally free delivery too. Ideas change the planet, particularly when they're written. The picture of a few of the dresses has been displayed together with the color so that it will become simple for the buyer to produce the best choice. Real-life situations such as these offer believable, concrete ideas for quick stories.

Democracy A Truly Human Way Of Living - 977 Words

Democracy to me always had a propagandist sort of vibe to it. When presented pop culture and movies, every instance the subject of democracy arises, it is also accompanied by some US plot to overthrow some South American communist regime. I identified democracy as a political form, a political tool, and my most preferred system of government. The American philosopher John Dewey, however, looks past the veil that democracy’s political and economic purposes produce and examines democracy instead as a way of life. Dewey identifies democracy as a truly human way of living, because it demands the participation of all the human beings that reside within its form to contribute to the values the system is purposed to provide for. Voting is the mechanism that allows the participants of a democracy to contribute and maintain those values, and honor the foundations that allow democracy to survive, while giving their participants’ equal opportunity to live and be their best. To int roduce, to Dewey, the common perception of democracy is hardly fitting of the perception I initially exposed. Dewey expands my common idea of democracy by referring to it as a â€Å"way of living†, but in the general political and governmental sense dictates it as, â€Å"the best means so far found, for realizing ends that lie in the wide domain of human relationships and the development of human personality. (1110)† Dewey understands democracy to be a social way to act as an individual. Democracy enforces andShow MoreRelatedDemocracy By John Dewey : Democracy888 Words   |  4 PagesDemocracy to me always had a propagandist vibe to it. In pop culture and movies, every instance the subject of democracy arises, it is also accompanied by some US plot to overthrow some South American communist regime. I identified democracy as a political form, a political tool, and my most preferred system of government. 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