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OUMH 2103ENGLISH FOR SCIENCE AND TECHNICAL PURPOSESNO. MATRIKULASI

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: norddin_77@oum.com.myPUSAT PEMBELAJARAN: KELANTAN LEARNING CENTRERecent research shows that the consumption of junk food is a major factor in poor diet and this is detrimental to health. Some people believe that better health education is the answer to this problem but others disagree. What is your opinion?

Introduction

Educating people regarding healthy life style would make them aware of hazards caused by fast food and beneficiaries of good healthy food. Therefore they will certainly try to avoid those junky items. As the proverb says Prevention is better than cure health education should be initiated from childhood, This would really create a positive influence on their daily lifestyle. So when they are grown up into adults there is less probability for them to get diverted into the wrong path.There are lot of other social factors, which forces the man to turn towards fast food. Few among them are busy work schedule, advertisement that mainly attracts younger age group, availability of these foods at a cheaper rate and so on. Steps should be taken to prevent these such as ensuring appropriate time and food is provided to the employees. Few more steps that should be considered taken are putting a ban to all the advertisements related to fast food and by prohibiting children from going to these shops. In this 21st century majority of the people are leading an unhealthy lifestyle. Eating food rich in calories has also become a widespread practice. It should be regarded as an issue of serious concern. One sensible approach, to reduce the intake of fast food is through educating people regarding healthy habits. In this essay, I would like to outline a few more approaches which could also contribute for a better health.

Junk food is a major factor in poor diet and this is detrimental to healthFood makes us who we are. If we talk about physical strength, presence of mind, our height, weight etc all these things depend on the type of food we eat. Food provides us nutrients, vitamins and minerals which are required for our growth and wellbeing. Sadly, not all food is good for us and for our health. The foods that are not good for our health are fast foods or junk foods (generally fried food). Most fried foods are processed food; thus are not in their natural state. Fried food is generally high in calories. An unhealthy fried patty burger, alone, contains over 1,200 calories. Eating food high in calories will increase your risk of being obese as your body will use the desired number of calories (energy) for work and then it will store the excessive calories as fat making you obese. Hereis a list of top reasons why fast (read: Junk fried, salty, greasy) food is bad for health.When you raise the subject of over-eating and obesity, you often see people at their worst. The comment threads discussing these issues reveal a legion of bullies who appear to delight in other people's problems.When alcoholism and drug addiction are discussed, the tone tends to be sympathetic. When obesity is discussed, the conversation is dominated by mockery and blame, though the evidence suggests that it may be driven by similar forms of addiction.But this problem belongs to all of us. Even if you can detach yourself from the suffering caused by diseases arising from bad diets, you will carry the cost, as a growing proportion of the health budget will be used to address them. The cost measured in both human suffering and money could be far greater than we imagined.

The consumption of fast foods has been increased around the world over last 50 years. Foods such as French fries, hamburgers and chips, which constitutes huge amount of fat and salt, are harmful for health. Some people believe that increasing the level of awareness of society about deterioration of this group of foods can decrease the consumption of them. I personally believe that affordable, convenient and attractive characteristics of junk food are dominated and education itself cannot change peoples mind to reduce utilizing of fast foods. Two main reasons will be argued accordingly.First of all, increasing peoples knowledge about the harms of low nutrition foods along with the probable ailments caused by them cannot prevent reducing of the consumption of such food. As the short term effects of using junk foods such as low price, easy access and time saving nature of junk foods pursue people to continue their nutrition habits. The long term impacts of this food especially in todays modern life style will be ignored commonly. A good illustration of that is climbing the demand for fast foods which result in increasing fast food restaurants and junk food production factories. Furthermore, the variety of fast foods and attractive appearance of junk foods, absorb peoples attention. Although, several TV programme and conferences have been held to discuss about substituting of rich nutrition food with junk foods in family daily food usage; on the contrary same channels broadcast attractive advertisement for junk foods. While many know that junk food and fast food are associated with an increase in obesity, heart disease, high blood pressure, cancer, tooth decay, and other maladies, and that vegetables and fruit are what they should eat, the popularity of fast food more aptly labeled junk food continues to grow. These salty snack foods, candy, gum, sugary desserts, fried fast food, and carbonated beverages are some of the major food groups within this category. Junk foods are BAD for your health.They taste so good but constant eatingof them can get you into a lot of trouble.Obesity is not caused by eating too muchfood but rather too much of the wrong food.

1. Junk food contains a lot of empty calories.

2. Junk food contains saturated fat that will make you fat.

3. Junk food is very low in nutrients.

4. Junk food contains too much sugar (More sugar=obesity+tooth decay).Generally, these contain minimal amounts of protein, vitamins, minerals, fiber and lots of calories from sugar or fat.As any busy person knows, eating healthy may not always seem realistic. Children need to be ferried to soccer and ballet practice. There are work projects, laundry, family crises, changing the cars oil all of which have to be done. Quality options are often substituted with highly processed boxed meals.Not to mention that depending on where you live, eating right may appear virtually impossible. A drive down a main street of any sized town or city engulfs the senses in an onslaught of bright colors, flashing signs, and enticing slogans all designed to make you crave a quick-fix meal.a.Fast food contain more unhealthy fat.

Most of theconvenient foods contain high levels of saturated fat. This type of fat is mostly derived from animal products such as meat, eggs and butter. Palm oil and coconut oil also contain significant amounts of saturated fat.Eating too much saturated fat can increase bad cholesterol level in the blood. Elevated levels of cholesterol is the main cause of heart attack, stroke and peripheral vascular diseases.Another type of fat presents in these food is called trans fat, which is the worst type of fat. We do not need to eat trans fat, even in tinyamounts.Consumption of trans fat is linked to elevated levels of bad cholesterol (LDL) in the blood. In addition, it can lower the amount of goodcholesterol(HDL) in you body.

b.Fast foods are high in sodium.

Sodium plays several important roles in our body. We need to consume certain amount of sodium everyday.However, taking too much salt is bad for the body. It can cause high blood pressure, obesity, andosteoporosis. In addition, experts believed that over-consumption of salt is linked to increased risk of developing bowl cancer.An average adult need to consume about 1200mg sodium per day. Many of the convenient foods contain far more than that amount.For example; KFC double down sandwich contain 1880 mg of sodium. Similarly, McDonald's Angus bacon and cheese contain 2070 mg of sodium.Imagine you eat one of these items for your one meal time. then what are you going to eat for the rest of the day?Eating too much fast food is bad for your health because they contain more calories, more unhealthy fay, and more salt. They can lead to obesity, high blood pressure, and coronary heart diseases.Junk food is food that is calorie-dense and nutrient poor. In recent decades, junk food, fast food and convenience food consumption in the United States have increased dramatically, with 25 percent of people now consuming predominantly junk food diets. This trend has occurred concurrently with rising epidemics of numerous chronic diseases and accounts for a long list of reasons why eating junk food is bad.

Obesity

Junk food plays a major role in the obesity epidemic. By the year 2050, the rate of obesity in the U.S. is expected to reach 42 percent, according to researchers at Harvard University. Children who eat fast food as a regular part of their diets consume more fat, carbohydrates and processed sugar and less fiber than those who do not eat fast food regularly. Junk food in these children's diets accounts for 187 extra calories per day, leading to 6 additional pounds of weight gain per year. Obesity increases your risk for cardiovascular disease, diabetes and many other chronic health conditions.

Diabetes

Your insulin levels become elevated when you eat processed sugars, such as those in soft drinks, white flour and other foods devoid of fiber and nutrients necessary to properly metabolize carbohydrates. Eating junk foods throughout the day causes chronically high insulin levels, which eventually prompts your cells to begin to ignore this important hormone, resulting in a condition known as insulin resistance. Ultimately, obesity and Type 2 diabetes may set in. Since the 1980s, Type 2 diabetes, which was minimal in teenagers, has risen to 15 percent.

Depression

Junk food may lead to depression in teenagers, according to Andrew F. Smith, author of the book "Fast Food and Junk Food: An Encyclopedia of What We Love to Eat." Hormonal changes at puberty make teens more susceptible to mood and behavioral swings. A healthy diet plays a part in keeping hormone levels on an even keel, while a diet high in junk food falls short of these requirements. Consuming trans fats, saturated fats and processed food is associated with up to 58 percent increase in risk of depression.

Nutrient Deficiencies

Processing that removes vitamins, minerals and fiber makes junk foods into the sources of empty calories that nutritionists disparage. Children who eat a lot of junk foods may develop nutritional deficiencies that lead to low energy, mood swings, sleep disturbance and poor academic achievement, among other health conditions, according to the University of New Hampshire Cooperative Extension.

Sodium

High sodium levels are a defining characteristic of many junk foods and one of the contributing factors to the overconsumption of salt that typifies the Western diet and contributes to high blood pressure and heart, liver and kidney diseases, according to Harvard Health Publications. The average American eats five to 10 times more salt than the 2,300 milligrams per day recommended by the U.S. Dietary Guidelines for Americans. Considering the high rates of high blood pressure among Americans, that level should be even lower -- about 1,500 milligrams per day -- for 70 percent of adults. However, the trend since 1988 shows that fewer people with hypertension adhere to a low-sodium diet now than did then.Top reason not to eat junk foodDisgusting animal conditions

You've seen those horrible movies about how poorly animals are kept when they're being led to slaughter, and they aren't just showing you those heart-wrenching photos for the ratings. Many of these factory-farmed animals are kept in such a small space they are forced to stand in their own feces, have osteoporosis and joint pain because of their confinement and some chickens get their beaks cut off so they don't go nuts and attack each other because of the small corridors. To keep the animals from getting sick in these conditions,they are pumped full of antibiotics, which often end up in our food. That's not only making us want to stop eating fast food, it's making us want to be vegan.

Weird ingredients

I'm sorry, what is in my food?According to the Matador Network, some fast food's chicken nuggets contain a chemical preservative called tertiary butylhydroquinone, which is derived from a petroleum. Yep, the stuff you put into your car. That's not all, either. Some chicken products are mechanically separated, which means those scraps that would normally go to waste are ending up in your nuggets. Plus, if you were even tostudy the ingredients in your favorite meals, you'd be shocked to see how many of them are chemical preservatives, artificial coloring, monosodium glutamate and more.

Low food quality

It doesn't take an expert to see that most fast food chains don't use the highest quality of ingredients. You can tell by the rubbery patty, the wilted lettuce leaves and the extra-chewy chicken. They use the cheapest parts to make the products so when you're eating your hamburger you have no darn clue what part of the cow it came from, and, heck, if it's even cow you're eating! Here's an idea, spend the extra few bucks and make your own burger from meat you bought yourself.

Food preparation

[or lack of]

It's called fast food for a reason, friends. Most of the meals you get aren't cooked with thought or love; they actually aren't even cooked on a stove. Many are unwrapped from their frozen containers and thrown into a dirty microwave. This saves the managers the time and money it would take to teach the cooks how to prepare the food properly and not worry about cross contamination. It saves their butts but doesn't make yours look any prettier.Trans fats

You haven't heard that word in a while, probably because it was banned from a few restaurants. Why? It can raise your LDL cholesterol, or bad cholesterol, leading to a heart attack or cardiac arrest. However, not all fast food restaurants are required to list trans fat content on menus, so it's possible the food you're eating may still have it, and lots of it. Fast food items particularly high in trans fats include French fries, fried fish filet sandwiches and fried chicken, for example.Slime

Now, you've heard all about the pink slime, and, thankfully, it's not something many of the restaurants use anymore to preserve their meats. But, that's not the only slime you may find at these fast food joints. In fact, a few fast food restaurants in Wrigley Field were shut down because they hadblack slime on their ice machines! Before you take a slurp of that diet Coke, make sure you aren't drinking bacteria-infested slime instead

Conclusion

The fast food culture has reached global proportions and many restaurant chains are found worldwide. The Mayo Clinic warns that fast food consumption is generally unhealthy and is leading to an alarming increase in obesity in both children and adults. It is also a culprit in cardiovascular disease, which affects the heart and arteries. Fast food can increase the risk of atherosclerosis, or hardening and narrowing of the arteries, heart disease and stroke due to the types of ingredients it contains and the amounts people typically consume.Fast food meals often include beverages such as fruit juice, milkshakes, smoothies and sodas that are high in sugar and calories. A 12-ounce soda contains 9 teaspoons of sugar and 140 calories. An article published in the medical journal "Pediatrics" warns that high sugar consumption can lead to obesity and an increase in Type 2 diabetes in both adults and children. All types of diabetes can have consequences for the body including diseased arteries, according to the American Diabetes Association. Although diet sodas have fewer calories, they may encourage poor food choices by increasing sugar cravings.

References

1. Jago R, Baranowski T, Baranowski JC. Fruit and vegetable availability: a micro environmental mediating variable? Public Health Nutr. 2007; 10:6819.

2. Larson NI, Neumark-Sztainer D, Jannan PJ, Story M. Family meals during adolescence are associated with higher diet quality and healthful meal patterns during young adulthood. J Am Diet Assoc. 2007; 107:150210.

3. Sen B. Frequency of family dinner and adolescent body weight status: evidence from the national longitudinal survey of youth, 1997. Obesity (Silver Spring). 2006; 14:226676.

4. Taveras EM, Rifas-Shiman SL, Berkey CS, Rockett HR, Field AE, Frazier AL, et al. Family dinner and adolescent overweight. Obes Res. 2005; 13:9006.

5. Gable S, Chang Y, Krull JL. Television watching and frequency of family meals are predictive of overweight onset and persistence in a national sample of school-aged children. J Am Diet Assoc. 2007; 107:5361.

6. Fulkerson JA, Neumark-Sztainer D, Hannan PJ, Story M. Family meal frequency and weight status among adolescents: cross-sectional and 5-year longitudinal associations. Obesity (Silver Spring). 2008; 16:252934.

7. Singh GK, Siahpush M, Hiatt RA, Timsina LR. Dramatic Increases in Obesity and Overweight Prevalence and Body Mass Index Among Ethnic-Immigrant and Social Class Groups in the United States, 1976-2008. J Community Health. 2010.

8. Darmon N, Drewnowski A. Does social class predict diet quality? Am J Clin Nutr. 2008; 87:110717.

9. Dubowitz T, Acevedo-Garcia D, Salkeld J, Lindsay AC, Subramanian SV, Peterson KE. Lifecourse, immigrant status and acculturation in food purchasing and preparation among low-income mothers. Public Health Nutr. 2007; 10:396404.PART B (20 marks)

The following diagram shows how greenhouse gases trap energy from the Sun.

Energy from the SunIntroduction

Inthe1850sBritishphysicist John Tyndall investigated the transmission of radiant heat through gases and vapors.Greenhouse Effect,thecapacityofcertain gases in the atmosphere to trap heat emitted from the Earths surface, thereby insulating and warming the Earth. Without the thermal blanketing of the natural greenhouse effect, the Earths climate would be about 33 Celsius degrees (about 59 Fahrenheit degrees) cooler too cold for most living organisms to survive. Scientistscallthisunnatural heating effect global warming and blame it for an increase in the Earths surface temperature of about 0.6 Celsius degrees (about 1 Fahrenheit degree) over the last nearly 100 years. Without remedial measures, many scientists fear that global temperatures will rise 1.4 to 5.8 Celsius degrees (2.5 to 10.4 Fahrenheit degrees) by 2100. These warmer temperatures could melt parts of polar ice caps and most mountain glaciers, causing a rise in sea level of up to 1 m (40 in) within a century or two, which would flood coastal regions. Global warming could also affect weather patterns causing, among other problems, prolonged drought or increased flooding in some of the worlds leading agricultural regions.

Describing how greenhouse gases trap energy from the Sun.

In 1896 he calculated that doubling the natural concentrations of carbon dioxide in the atmosphere would increase global temperatures by 4 to 6 Celsius degrees (7 to 11 Fahrenheit degrees), a calculation that is not too far from todays estimates using more sophisticated methods. Arrhenius correctly predicted that when Earths temperature warms, water vapor evaporation from the oceans increases. Thegreenhouseeffect has warmed the Earth for over 4 billion years. Now scientists are growing increasingly concerned that human activities may be modifying this natural process, with potentially dangerous consequences. Since the advent of the Industrial Revolution in the 1700s, humans have devised many inventions that burn fossil fuels such as coal, oil, and natural gas. Burning these fossil fuels, as well as other activities such as clearing land for agriculture or urban settlements, releases some of the same gases that trap heat in the atmosphere, including carbon dioxide, methane, and nitrous oxide. These atmospheric gases have risen to levels higher than at any time in the last 420,000 years. As these gases build up in the atmosphere, they trap more heat near the Earths surface, causing Earths climate to become warmer than it would naturally.The greenhouse effect increases the temperature of the Earth by trapping heat in our atmosphere. The greenhouse effect keeps the temperature of the Earth higher than it would be if direct heating by the Sun was the only source of warming. When sunlight reaches the surface of the Earth, some of it is absorbed which warms the ground and some bounces back to space as heat. Greenhouse gases that are in the atmosphere absorb and then redirect some of this heat back towards the Earth. Tyndall found that nitrogen and oxygen, the two most common gases in the atmosphere, had no heat-absorbing properties. He then went on to measure the absorption of infrared radiation by carbon dioxide and water vapor, publishing his findings in 1863 in a paper titled On Radiation Through the Earths Atmosphere. SwedishchemistSvante August Arrhenius, best known for his Nobel Prize-winning work in electrochemistry, also advanced understanding of the greenhouse effect. The main feedback gas of the greenhouse effect is: Water vapor

Carbon dioxide, methane, nitrous oxide and the fluorinated gases are all well-mixed gases in the atmosphere that do not react to changes in temperature and air pressure and thus do not condense and become rain or snow. Water vapor on the other hand, is a highly active component of the climate system that responds rapidly to changes in conditions by either condensing into rain or snow, or evaporating to return to the atmosphere. Thus the impact of the greenhouse effect is primarily circulated through water vapor, and it acts as a fast feedback.

Carbon dioxide and the other non-condensing greenhouse gases are the key gases within the Earth's atmosphere that sustain the greenhouse effect and control its strength. Water vapor is a fast-acting feedback but it is controlled by the radiative forcings supplied by the non-condensing greenhouse gases.In fact, the greenhouse effect would collapse were it not for the presence of carbon dioxide and the other non-condensing greenhouse gases. Together the feedback by the condensing and the forcing by the non-condensing gases within the atmosphere both play an important role in the greenhouse effect. So as long as the amount of greenhouse gases in the atmosphere and the amount of energy from the sun remain the same, the average temperature on Earth should also be constant.

The greenhouse effect is a major factor in keeping our Earth warm because it keeps some of the planet's heat that would otherwise escape from the atmosphere out to space. In fact, without the greenhouse effect the Earth's average global temperature would be much colder and life on Earth as we know it would not be possible. The difference between the Earth's actual average temperature 14.4 C (57.9 F) and the expected effective temperature just with the Sun's radiation -18.1 C (-0.6 F) gives us the strength of the greenhouse effect, which is 32.5 C. Thegreenhouseeffect results from the interaction between sunlight and the layer of greenhouse gases in the Earth's atmosphere that extends up to 100 km (60 mi) above Earth's surface. Sunlight is composed of a range of radiant energies known as the solar spectrum, which includes visible light, infrared light, gamma rays, X rays, and ultraviolet light. When the Suns radiation reaches the Earths atmosphere, some 25 percent of the energy is reflected back into space by clouds and other atmospheric particles. About 20 percent is absorbed in the atmosphere. For instance, gas molecules in the uppermost layers of the atmosphere absorb the Suns gamma rays and X rays. The Suns ultraviolet radiation is absorbed by the ozone layer, located 19 to 48 km (12 to 30 mi) above the Earths surface.In addition, some of the Suns radiation that is absorbed by the Earths surface becomes heat energy in the form of long-wave infrared radiation, and this energy is released back into the atmosphere. Certaingasesintheatmosphere, including water vapor, carbon dioxide, methane, and nitrous oxide, absorb this infrared radiant heat, temporarily preventing it from dispersing into space. As these atmospheric gases warm, they in turn emit infrared radiation in all directions. Some of this heat returns back to Earth to further warm the surface in what is known as the greenhouse effect, and some of this heat is eventually released to space. This heat transfer creates equilibrium between the total amount of heat that reaches the Earth from the Sun and the amount of heat that the Earth radiates out into space. This equilibrium or energy balance the exchange of energy between the Earths surface, atmosphere, and space is important to maintain a climate that can support a wide variety of life.

Theheat-trappinggases in the atmosphere behave like the glass of a greenhouse. They let much of the Suns rays in, but keep most of that heat from directly escaping. Because of this, they are called greenhouse gases. Without these gases, heat energy absorbed and reflected from the Earths surface would easily radiate back out to space, leaving the planet with an inhospitable temperature close to 19C (2F), instead of the present average surface temperature of 15C (59F).Toappreciatetheimportance of the greenhouse gases in creating a climate that helps sustain most forms of life, compare Earth to Mars and Venus. Mars has a thin atmosphere that contains low concentrations of heat-trapping gases. As a result, Mars has a weak greenhouse effect resulting in a largely frozen surface that shows no evidence of life. In contrast, Venus has an atmosphere containing high concentrations of carbon dioxide. This heat-trapping gas prevents heat radiated from the planets surface from escaping into space, resulting in surface temperatures that average 462C (864F) too hot to support life. Earthsatmosphereis primarily composed of nitrogen (78 percent) and oxygen (21 percent). These two most common atmospheric gases have chemical structures that restrict absorption of infrared energy. Only the few greenhouse gases, which make up less than 1 percent of the atmosphere, offer the Earth any insulation. Greenhouse gases occur naturally or are manufactured. The most abundant naturally occurring greenhouse gas is water vapor, followed by carbon dioxide, methane, and nitrous oxide. Human-made chemicals that act as greenhouse gases include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs).

a.Water Vapor

About50percentofthe Suns energy, largely in the form of visible light, passes through the atmosphere to reach the Earths surface. Soils, plants, and oceans on the Earths surface absorb about 85 percent of this heat energy, while the rest is reflected back into the atmosphere most effectively by reflective surfaces such as snow, ice, and sandy deserts. Watervaporisthemost common greenhouse gas in the atmosphere, accounting for about 60 to 70 percent of the natural greenhouse effect. Humans do not have a significant direct impact on water vapor levels in the atmosphere. However, as human activities increase the concentration of other greenhouse gases in the atmosphere (producing warmer temperatures on Earth), the evaporation of oceans, lakes, and rivers, as well as water evaporation from plants, increase and raise the amount of water vapor in the atmosphere.

b.Carbon Dioxide

Carbondioxideconstantly circulates in the environment through a variety of natural processes known as the carbon cycle. Volcanic eruptions and the decay of plant and animal matter both release carbon dioxide into the atmosphere. In respiration, animals break down food to release the energy required to build and maintain cellular activity. A byproduct of respiration is the formation of carbon dioxide, which is exhaled from animals into the environment. Oceans, lakes, and rivers absorb carbon dioxide from the atmosphere. Through photosynthesis, plants collect carbon dioxide and use it to make their own food, in the process incorporating carbon into new plant tissue and releasing oxygen to the environment as a byproduct. Inordertoprovideenergy to heat buildings, power automobiles, and fuel electricity-producing power plants, humans burn objects that contain carbon, such as the fossil fuels oil, coal, and natural gas; wood or wood products; and some solid wastes. When these products are burned, they release carbon dioxide into the air. In addition, humans cut down huge tracts of trees for lumber or to clear land for farming or building. This process, known as deforestation, can both release the carbon stored in trees and significantly reduce the number of trees available to absorb carbon dioxide.Asaresultofthesehuman activities, carbon dioxide in the atmosphere is accumulating faster than the Earths natural processes can absorb the gas. By analyzing air bubbles trapped in glacier ice that is many centuries old, scientists have determined that carbon dioxide levels in the atmosphere have risen by 31 percent since 1750. And since carbon dioxide increases can remain in the atmosphere for centuries, scientists expect these concentrations to double or triple in the next century if current trends continue.

What Causes the Greenhouse Effect?Life on earth depends on energy from the sun. About 30 percent of the sunlight that beams toward Earth is deflected by the outer atmosphere and scattered back into space. The rest reaches the planet's surface and is reflected upward again as a type of slow-moving energy called infrared radiation.

The heat caused by infrared radiation is absorbed by "greenhouse gases" such as water vapor, carbon dioxide, ozone and methane, which slows its escape from the atmosphere.

Although greenhouse gases make up only about 1 percent of the Earth's atmosphere, they regulate our climate by trapping heat and holding it in a kind of warm-air blanket that surrounds the planet.

This phenomenon is what scientists call the "greenhouse effect." Without it, scientists estimate that the average temperature on Earth would be colder by approximately 30 degrees Celsius (54 degrees Fahrenheit), far too cold to sustain our current ecosystem.

How Do Humans Contribute to the Greenhouse Effect?While the greenhouse effect is an essential environmental prerequisite for life on Earth, there really can be too much of a good thing.

The problems begin when human activities distort and accelerate the natural process by creating more greenhouse gases in the atmosphere than are necessary to warm the planet to an ideal temperature.

Burning natural gas, coal and oil -including gasoline for automobile engines-raises the level of carbon dioxide in the atmosphere.

Some farming practices and land-use changes increase the levels of methane and nitrous oxide.

Many factories produce long-lasting industrial gases that do not occur naturally, yet contribute significantly to the enhanced greenhouse effect and "global warming" that is currently under way.

Deforestation also contributes to global warming. Trees use carbon dioxide and give off oxygen in its place, which helps to create the optimal balance of gases in the atmosphere. As more forests are logged for timber or cut down to make way for farming, however, there are fewer trees to perform this critical function.

Population growth is another factor in global warming, because as more people use fossil fuels for heat, transportation and manufacturing the level of greenhouse gases continues to increase. As more farming occurs to feed millions of new people, more greenhouse gases enter the atmosphere.

Ultimately, more greenhouse gases means more infrared radiation trapped and held, which gradually increases the temperature of the Earth's surface and the air in the lower atmosphere.

The Average Global Temperature is Increasing QuicklyToday, the increase in the Earth's temperature is increasing with unprecedented speed. To understand just how quickly global warming is accelerating, consider this:

During the entire 20th century, the average global temperature increased by about 0.6 degrees Celsius (slightly more than 1 degree Fahrenheit).

Using computer climate models, scientists estimate that by the year 2100 the average global temperature will increase by 1.4 degrees to 5.8 degrees Celsius (approximately 2.5 degrees to 10.5 degrees Fahrenheit).

Not All Scientists AgreeWhile the majority of mainstream scientists agree that global warming is a serious problem that is growing steadily worse, there are some who disagree. John Christy, a professor and director of the Earth System Science Center at the University of Alabama in Huntsville is a respected climatologist who argues that global warming isn't worth worrying about.Christy reached that opinion after analyzing millions of measurements from weather satellites in an effort to find a global temperature trend. He found no sign of global warming in the satellite data, and now believes that predictions of global warming by as much as 10 degrees Fahrenheit by the end of the 21st century are incorrect.Scientists agree that even a small increase in the global temperature would lead to significant climate and weather changes, affecting cloud cover, precipitation, wind patterns, the frequency and severity of storms, and the duration of seasons.

Rising temperatures would raise sea levels as well, reducing supplies of fresh water as flooding occurs along coastlines worldwide and salt water reaches inland.

Many of the worlds endangered species would become extinct as rising temperatures changed their habitat.

Millions of people also would be affected, especially poor people who live in precarious locations or depend on the land for a subsistence living.

Certain vector-borne diseases carried by animals or insects, such as malaria, would become more widespread as warmer conditions expanded their range.

Carbon Dioxide Emissions are the Biggest ProblemCurrently, carbon dioxide accounts for more than 60 percent of the enhanced greenhouse effect caused by the increase of greenhouse gases, and the level of carbon dioxide in the atmosphere is increasing by more than 10 percent every 20 years.If emissions of carbon dioxide continue to grow at current rates, then the level of the gas in the atmosphere will likely double, or possibly even triple, from pre-industrial levels during the 21st century.

Climate Changes are InevitableAccording to the United Nations, some climate change is already inevitable because of emissions that have occurred since the dawn of the Industrial Age. While the Earths climate does not respond quickly to external changes, many scientists believe that global warming already has significant momentum due to 150 years of industrialization in many countries around the world. As a result, global warming will continue to affect life on Earth for hundreds of years, even if greenhouse gas emissions are reduced and the increase in atmospheric levels halted.

What is Being Done to Reduce Global Warming?To lessen those long-term effects, many nations, communities and individuals are taking action now to reduce greenhouse gas emissions and slow global warming by reducing dependence on fossil fuels, increasing the use of renewable energy, expanding forests, and making lifestyle choices that help to sustain the environment. Whether they will be able to recruit enough people to join them, and whether their combined efforts will be enough to head off the most serious effects of global warming, are open questions that can only be answered by future developments.

Conclusion

Aerosols,alsoknownas particulates, are airborne particles that absorb, scatter, and reflect radiation back into space. Clouds, windblown dust, and particles that can be traced to erupting volcanoes are examples of natural aerosols. Human activities, including the burning of fossil fuels and slash-and-burn farming techniques used to clear forestland, contribute additional aerosols to the atmosphere. Although aerosols are not considered a heat-trapping greenhouse gas, they do affect the transfer of heat energy radiated from the Earth to space. The effect of aerosols on climate change is still debated, but scientists believe that light-colored aerosols cool the Earths surface, while dark aerosols like soot actually warm the atmosphere. The increase in global temperature in the last century is lower than many scientists predicted when only taking into account increasing levels of carbon dioxide, methane, nitrous oxide, and fluorinated compounds. Some scientists believe that aerosol cooling may be the cause of this unexpectedly reduced warming. However,scientistsdo not expect that aerosols will ever play a significant role in offsetting global warming. As pollutants, aerosols typically pose a health threat, and the manufacturing or agricultural processes that produce them are subject to air-pollution control efforts. As a result, scientists do not expect aerosols to increase as fast as other greenhouse gases in the 21st century.

The "greenhouse effect" often gets a bad rap because of its association with global warming, but the truth is we couldn't live without it.

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