Introduction:
Greenhouses can be divided into glass greenhouses and plastic greenhouses. Plastics mostly used are PEfilm and multiwall sheet in PC or PMMA. Commercial glass greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, lighting and may be automatically controlled by a computer.
The glass used for a greenhouse works as a barrier to air flow and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. A miniature greenhouse is known as a cold frame.
A greenhouse (also called a glasshouse) is a building where plants are grown.A greenhouse is a structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation from the sun is absorbed by plants, soil, and other things inside the building. Glass is transparent to this radiation. The warmed structures and plants inside the greenhouse re-radiate this energy in the infra-red, to which glass is partly opaque, and that energy is trapped inside the glasshouse. Although there is some heat loss due to conduction, there is a net increase in energy (and therefore temperature) inside the greenhouse. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. These structures range in size from small sheds to very large buildings.
Greenhouses can be divided into glass greenhouses and plastic greenhouses. Plastics mostly used are Peril and mutual sheet in PC or PMMA. Commercial glass greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, lighting and may be automatically controlled by a computer.
The glass used for a greenhouse works as a barrier to air flow and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the auto vent automatic cooling system. A miniature greenhouse is known as a cold frame.
Greenhouse Effect:
The term ‘Greenhouse Effect’ refers to the way certain gases trap heat in the atmosphere, much as the glass in a greenhouse prevents rising warm air from escaping.
Enhancement of this effect by human activity – not the effect itself, which is entirely natural – has experts worried. In fact, Earth, 93 million miles from its energy source – the sun – would be about 32° C colder if certain atmospheric gases did not trap heat. We probably owe existence of life on this planet to the greenhouse effect.
Whether radiation is absorbed depends on the size & type of objects through which it travels. About half of sunlight hitting the outer atmosphere reaches the surface, where it transfers energy to land and water. The surface then sheds that energy as heat, largely infrared radiation ( IR ). If the air contained nothing but its main components almost all of the energy emitted at the surface would radiate uninterrupted back into space.
But in fact, nearly 90 % of that long-wave-length radiation is caught by clouds and gases, which sends much of it down again. The astonishing result is that Earth’s surface is hit daily with twice
as much energy from re-radiated IR out of the atmosphere as from incoming sunlight.
That is because some kinds of molecules, known collectively as ‘greenhouse’ gases, are just the right size and configuration to trap long-wavelength IR and re-radiate it. Most greenhouse gases elude natural chemical cleaning processes in the atmosphere, and many stay aloft from decades to centuries.
However, the term ‘global warming’ is deceptive because it suggests that the paramount issue is average temperature. But much more important is a change in the way water moves around. As Earth’s surface warms, most of the energy goes into evaporating water. When rising water vapor condenses again, it sheds that energy as heat into the air. Even a modest amount of global warming would cause a substantial increase in air moisture because for every 1 degree Celsius that its temperature rises, the atmosphere can hold 6 percent more water vapor.
That means a substantial warming would produce more clouds and rain on average and more violent precipitation in some areas and severe drying of soils in many other locations. A greater cloud cover would explain why warming seems to have increased most at nighttime and in winter. During the day, clouds keep the land cooler by shading the surface, while at night they form a barrier that confines heat close to the surface.
Excerptedfrom ‘Climate Change Primer’
in the Washington Post 1997
A greenhouse (also called a glasshouse) is a building where plants are grown.
A greenhouse is a structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation from the sun is absorbed by plants, soil, and other things inside the building. Glass is transparent to this radiation. The warmed structures and plants inside the greenhouse re-radiate this energy in the infra-red, to which glass is partly opaque, and that energy is trapped inside the glasshouse. Although there is some heat loss due to conduction, there is a net increase in energy (and therefore temperature) inside the greenhouse. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. These structures range in size from small sheds to very large buildings.
Greenhouses can be divided into glass greenhouses and plastic greenhouses. Plastics mostly used are PEfilm and multiwall sheet in PC or PMMA. Commercial glass greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, lighting and may be automatically controlled by a computer.
The glass used for a greenhouse works as a barrier to air flow and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. A miniature greenhouse is known as a cold frame.
Definition of Greenhouse Effect:
Greenhouse Effect — The warming of the Earth’s atmosphere attributed to a buildup of carbon dioxide or other gases; some scientists think that this build-up allows the sun’s rays to heat the Earth, while making the infra-red radiation atmosphere opaque to infra-red radiation, thereby preventing a counterbalancing loss of heat.
Greenhouse effect — The result of water vapor, carbon dioxide, and other atmospheric gases trapping radiant (infrared) energy, thereby keeping the earth’s surface warmer than it would otherwise be. Greenhouse gases within the lower levels of the atmosphere trap this radiation, which would otherwise escape into space, and subsequent re-radiation of some of this energy back to the Earth maintains higher surface temperatures than would occur if the gases were absent.
Greenhouse Effect — Atmospheric heating caused by solar radiation being readily transmitted inward through the earth’s atmosphere but longwave radiation less readily transmitted outward, due to absorption by certain gases in the atmosphere.
Steady increase in the Earth’s average lower atmosphere (near surface) temperature due to heat retention caused by the accumulation of greenhouse gases (including water vapor, carbon dioxide, methane, nitrous oxides, and chlorofluorocarbons or CFCs). These gases form a blanket around the earth that lets the incoming sun rays (short wave radiation) to pass through but blocks the reflected heat rays (long wave radiation) from going out into the space. Heat-retention is a natural phenomenon (essential to all life on earth) replicated in greenhouses where the glass roof traps radiant heat within an enclosed space. This build up of heat has drastically increased since industrial revolution in mid 19th century by fossil fuel burning. And further accelerated by CFC-emissions in the 20th century, leading to global warming (the year 1998, for example, was the warmest year in the recorded history). Each CFC molecule (which causes ozone-depletion also) is estimated to have 10,000 times more heat reflecting effect than a molecule of carbon dioxide. The greenhouse effect was first studied in 1896 by the Swedish Nobel-laureate (1903) chemist Svante Arrhenius (1859-1927) who called it hothouse effect. But its mathematical bases preceded its discovery and were published in 1824 by the French mathematician Jean-Baptiste-Joseph Fourier (1768-1830).
The History Of Greenhouses:
Greenhouses have come a long way since the wealthy Europeans and Americans used them to grow oranges and pineapples in glass structures known as orangeries and pineries. These structures became status symbols as well as a practical way to grow fruits, vegetables and exotic plants. One of the earliest known greenhouses was built around 30 A.D. for the Roman emperor Tiberius. Remember glass had not been invented so the “Specularium” was painstakingly fabricated from tiny translucent sheets of mica. All this was done to satisfy Tiberius’s cravings for cucumbers out of season. It wasn’t until 1599 that the first practical greenhouse was designed by Jules Charles a French botanist. It was built in (where else) Leiden Holland and used primarily to grow medicinal tropical plants. One of the favorite plants of the day came from the Tamarind (an Indian date) whose fruit was made into a curative drink.The idea caught on and greenhouses began spreading throughout Europe. The French, who had a love of a new fruit, the orange, began building orangeries to protect the trees from frost. These structures were cumbersome. One structure built by Soloman de Caus in 1619 in Heidelburg which held 340 orange trees. It had a removable roof that had to be painstakingly put up and taken down during the frost season.
Experimenting with angled glass walls and heating flues to improve the efficiency of greenhouses went on throughout the 17th century. New technologies and improved glass led to larger and more elaborate structures that housed plants simply to please the eyes and palates of the European aristocracy. The palace of Versailles was an example of the elaborate efforts of the royalty to build bigger and more spectacular orangeries. The Versailles orangery was more than 500 feet long, 42 feet wide, and 45 feet high. It had a southern exposure for light and heat. Despite the elaborateness of these structures, it was the Victorian age in England that ushered in the golden era of the greenhouse. By the end of the mid nineteenth century glass was plentiful and the prohibitive taxes were repealed. The wealthy began competing with each other to build the most elaborate greenhouse, again primarily just to grow citrus fruits and rare flowers. Little thought was given to using the greenhouse for a complete range of food production. The soaring conservatory at KewGardens in England is a prime example of the Victorian greenhouse. There is a replica in San Fransisco’s Golden GatePark called the Conservatory of Flowers.
In America the first greenhouse on record was built around 1737 by Andrew Faneuil, a wealthy Boston merchant. Like his European predecessors, Faneuil used it primarily to grow fruit. The concept spread slowly, since almost all greenhouses were built for the wealthy. George Washington, perhaps the richest man in America, craved pineapples and ordered a pinery built at Mt.Vernon so he could serve pineapples to his guests. By 1825, greenhouses were becoming increasingly common. Many of the greenhouses were heated by furnace warmed air; some were pit greenhouses built into the earth and heated largely by south facing windows. This is a design that remains highly practical today.
Indeed the modern concept of the greenhouse is simple and practical. No longer is it the private domain of the monied class but something anyone interested in gardening can have for relatively little cost. Today a greenhouse can go virtually anywhere there is space; it can be attached to a house, placed in a backyard or perched on a deck, roof or balcony. In addition greenhouses are becoming more automated, reducing the time and care owners much spend. With new materials available today such as aluminum, pvc piping, fiberglass, acrylic, and polycarbonate panels as well as pressure treated wood ensures the consumer that their greenhouse will stand the test of time. Long gone are the days of shattered glass and overheated/under heated greenhouses.
The idea of growing plants in environmentally controlled areas has existed since Roman times. The Roman emperor Tiberius ate a cucumber-like vegetable daily. The Roman gardeners used artificial methods (similar to the greenhouse system) of growing to have it available for his table every day of the year. Cucumbers were planted in wheeled carts which were put in the sun daily, then taken inside to keep them warm at night. The cucumbers were stored under frames or in cucumber houses glazed with either oiled cloth known as “speculation” or with sheets of serenity (a.k.a. lapis secularist), according to the description by Pliny the Elder.
Giant greenhouses in the Netherlands
The first modern greenhouses were built in Italy in the thirteenth century to house the exotic plants that explorers brought back from the tropics. They were originally called giardini botanici (botanical gardens). The concept of greenhouses soon spread to the Netherlands and then England, along with the plants. Some of these early attempts required enormous amounts of work to close up at night or to winterize. There were serious problems with providing adequate and balanced heat in these early greenhouses. Today the Netherlands as many of the largest greenhouses in the world, some of them so vast that they are able to produce millions of vegetables every year.
The French botanist Charles Lucien Bonaparte is often credited with building the first practical modern greenhouse in Leiden, Holland to grow medicinal tropical plants.
Originally on the estates of the rich, with the growth of the science of botany greenhouses spread to the universities. The French called their first greenhouses orangeries, since they were used to protect orange trees from freezing. As pineapples became popular pineries, or pineapple pits, were built. Experimentation with the design of greenhouses continued during the Seventeenth Century in Europe as technology produced better glass and construction techniques improved. The greenhouse at the Palace of Versailles was an example of their size and elaborateness; it was more than 500 feet long, 42 feet wide, and 45 feet high.
In the nineteenth Century the largest greenhouses were built. The conservatory at Kew Gardens in England is a prime example of the Victorian greenhouse. Although intended for both horticultural and non-horticultural exhibition these included London’s Crystal Palace, the New York Crystal Palace and Munich’s Glaspalast. Joseph Paxton, who had experimented with glass and iron in the creation of large greenhouses as the head gardener at Chatsworth, in Derbyshire, working for the Duke of Devonshire, designed and built the first, London’s Crystal Palace. A major architectural achievement in monumental greenhouse building were the Royal Greenhouses of Laeken (1874-1895) for King Leopold II of Belgium.
In Japan, the first greenhouse was built in 1880 by Samuel Cocking, a British merchant who exported herbs.
In the Twentieth Century the geodesic dome was added to the many types of greenhouses. A notable example is the Eden Project, in Cornwall.
Greenhouse structures adapted in the 1960s when wider sheets of polyethylene film became widely available. Hoop houses were made by several companies and were also frequently made by the growers themselves. Constructed of aluminium extrusions, special galvanized steel tubing, or even just lengths of steel or PVC water pipe, construction costs were greatly reduced. This meant many more greenhouses on smaller farms and garden centers. Polyethylene film durability increased greatly when more effective inhibitors were developed and added in the 1970s. These UV inhibitors extended the usable life of the film from one or two years up to 3 and eventually 4 or more years. Gutter connected greenhouses became more prevalent in the 1980s and 1990s. These greenhouses have two or more bays connected by a common wall, or row of support posts. Heating inputs were reduced as the ratio of floor area to roof area was increased substantially. Gutter connected greenhouses are now commonly used both in production and in situations where plants are grown and sold to the public as well. Gutter connected greenhouses are commonly covered with a double layer of polyethylene film with air blown between to provide increased heating efficiencies, or structured polycarbonate materials.
A greenhouse (also called a glasshouse) is a building where plants are grown.
A greenhouse is a structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation from the sun is absorbed by plants, soil, and other things inside the building. Glass is transparent to this radiation. The warmed structures and plants inside the greenhouse re-radiate this energy in the infra-red, to which glass is partly opaque, and that energy is trapped inside the glasshouse. Although there is some heat loss due to conduction, there is a net increase in energy (and therefore temperature) inside the greenhouse. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. These structures range in size from small sheds to very large buildings.
Uses of Green house effect:
Greenhouses protect crops from too much heat or cold, shield plants from dust storms and blizzards, and help to keep out pests. Light and temperature control allows greenhouses to turn inarable land into arable land, thereby improving food production in marginal environments.
Because greenhouses allow certain crops to be grown throughout the year, greenhouses are increasingly important in the food supply of high latitude countries. One of the largest greenhouse complexes in the world is in Almeria, Spain, where greenhouses cover almost 50,000 acres (200 km2). Sometimes called the sea of plastics.
Greenhouses are often used for growing flowers, vegetables, fruits, and tobacco plants. Bumblebees are the pollinators of choice for most greenhouse pollination, although other types of bees have been used, as well as artificial pollination. Hydroponics can be used in greenhouses as well to make the most use of the interior space.
Besides tobacco, many vegetables and flowers are grown in greenhouses in late winter and early spring, and then transplanted outside as the weather warms. Started plants are usually available for gardeners in farmers’ markets at transplanting time. Special greenhouse varieties of certain crops such as tomatoes are generally used for commercial production.
The closed environment of a greenhouse has its own unique requirements, compared with outdoor production. Pests and diseases, and extremes of heat and humidity, have to be controlled, and irrigation is necessary to provide water. Significant inputs of heat and light may be required, particularly with winter production of warm-weather vegetables.
Because the temperature and humidity of greenhouses must be constantly monitored to ensure optimal conditions, a wireless sensor network can be used to gather data remotely. The data is transmitted to a control location and used to control heating, cooling, and irrigation systems.
Causes of the Greenhouse Effect:
The Greenhouse effect is a much debated issue. Here are some details about the causes of the Greenhouse effect.
Humankind has progressed a lot over the years. However, this progress has come at a cost of the exploitation of nature many a times. Humans are the main reason for the pollution in nature.
Global warming has been a matter of concern for many years, with various man-made machines now contributing to Global Warming.
One of the main causes of Global Warming is the Green house effect. When the emission of infra-red radiation in the atmosphere warms a planet’s surface, it is known as the Green House Effect. The Greenhouse effect is a natural phenomena occurring on planet Earth.
There are natural as well as human-made causes of the greenhouse effect. The natural causes of the Green house effect are the emissions of gases like nitrous oxide, carbon-di-oxide, methane, ozone and water vapor.
The life on Earth depends entirely on the Sun. The energy for life is supplied by the Sun. Out of the total sunlight available, more than thirty percent is deflected into outer space. The rest is reflected and converted into slow moving energy called infrared radiation. This radiation is then trapped into the atmosphere by various gases like carbon-di-oxide, methane, ozone and water vapor. Therefore, it’s escape is slowed down. Out of these gases, carbon-di-oxide itself is responsible for the Green house effect.
The greenhouse effect is actually beneficial to the Earth. It is only when human-made processes increase its speed that the problems occur. One main problem is the oft repeated ‘Global Warming’.
One of the man-made causes of the Green House effect is deforestation. Deforestation increases the amount of carbon-di-oxide in the atmosphere. Also, due to the disappearance of trees, photosynthesis cannot take place. Deforestation causes of the greenhouse effect. Deforestation is rampant today due to the increase in human civilization. The levels of deforestation have increased by about nine percent in recent times. Also, the burning of wood causes it to decay, therefore releasing more carbon-dioxide into the atmosphere.
Greenhouse Gases also can be released into the atmosphere due to the burning of fossil fuels, oil, coal and gas. These materials are used increasingly and rampantly in Industries. Therefore Industries are also a major cause of the Greenhouse Effect.
Another man-made causes of the increase in the Green house effect due to the emission of such gases are any all electrical appliances. Even the humble refrigerator in the house emits gases which contribute to the Greenhouse effect. These gases are known as Chlorofluorocarbons (CFCs) and are used in refrigerators, aerosol cans, some foaming agents in the packaging industry, fire extinguisher chemicals and cleaners used in the electronic industry. Some processes of the cement manufacturing industries also act as a cause towards the Greenhouse effect.
Other man-made processes that contribute and are a cause to the Greenhouse effect are burning of gasoline, oil and coal. Apart from these, some farming and land-use processes are a cause of the Green house effect. Most factories also produce many gases which last for a longer time in the atmosphere. These gases contribute to the green-house effect and also the global warming on the planet. These gases are not naturally available in the atmosphere.
Population growth also is a indirect contributor and one of the causes of the Greenhouse effect. With the increase in population, the needs and wants of the people increase. Therefore, this increases the manufacturing processes as well as the industry processes. This results in the increase of the release of industrial gases which catalyse the green house effect. The increase in population also results in the increase of agricultural processes. Most man-made machines, like the automobile also contribute to the green house effect.
Global warming:
Global warming is the increase in the average temperature of Earth’s near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th century. Most of the observed temperature increase since the middle of the 20th century was caused by increasing concentrations of greenhouse gases, which results from human activity such as fossil fuel burning and deforestation. Global, a result of increasing concentrations of atmospheric aerosols that block sunlight from reaching the surface, has partially countered the effects of greenhouse gas induced warming.
Climate model projections summarized in the latest IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century. The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts.[4] Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects include changes in the frequency and intensity of extreme weather events, species extinctions, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional variations is uncertain.
The scientific consensus is that anthropogenic global warming is occurring. Nevertheless, political and public debate continues. The Kyoto Protocol is aimed at stabilizing greenhouse gas concentration to prevent a “dangerous anthropogenic interference”. As of November 2009, 187 states have signed and ratified the protocol.
Global mean surface temperature difference relative to the 1961–1990 average
Climate change:
Climate change is a change in the statistical distribution of weather over periods of time that range from decades to millions of years. It can be a change in the average weather or a change in the distribution of weather events around an average (for example, greater or fewer extreme weather events). Climate change may be limited to a specific region, or may occur across the whole Earth.
In recent usage, especially in the context of environmental policy, climate change usually refers to changes in modern climate. It may be qualified as anthropogenic climate change, more generally known as “global warming” or “anthropogenic global warming” (AGW).
For information on temperature measurements over various periods, and the data sources available, see temperature record. For attribution of climate change over the past century, see attribution of recent climate change.
Solar output
Variations in solar activity during the last several centuries based on observations of sunspots and beryllium isotopes.
The sun is the predominant source for energy input to the Earth. Both long- and short-term variations in solar intensity are known to affect global climate.
Three to four billion years ago the sun emitted only 70% as much power as it does today. If the atmospheric composition had been the same as today, liquid water should not have existed on Earth. However, there is evidence for the presence of water on the early Earth, in the Hadean and Archean eons, leading to what is known as the faint young sun paradox Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist[13] Over the following approximately 4 billion years, the energy output of the sun increased and atmospheric composition changed, with the oxygenation of the atmosphere around 2.4 billion years ago being the most notable alteration. These changes in luminosity, and the sun’s ultimate death as it becomes a red giant and then a white dwarf, will have large effects on climate, with the red giant phase possibly ending life on Earth.
Solar output also varies on shorter time scales, including the 11-year solar cycle and longer-term modulations.[15] Solar intensity variations are considered to have been influential in triggering the Little Ice Age, and some of the warming observed from 1900 to 1950. The cyclical nature of the sun’s energy output is not yet fully understood; it differs from the very slow change that is happening within the sun as it ages and evolves. While most research indicates solar variability has induced a small cooling effect from 1750 to the present, a few studies point toward solar radiation increases from cyclical sunspot activity affecting global warming.
Volcanism
Volcanism is a process of conveying material from the crust and mantle of the Earth to its surface. Volcanic eruptions, geysers, and hot springs, are examples of volcanic processes which release gases and/or particulates into the atmosphere.
Eruptions large enough to affect climate occur on average several times per century, and cause cooling (by partially blocking the transmission of solar radiation to the Earth’s surface) for a period of a few years. The eruption of Mount Pinatubo in 1991, the second largest terrestrial eruption of the 20th century (after the 1912 eruption of Novarupta) affected the climate substantially. Global temperatures decreased by about 0.5 °C (0.9 °F). The eruption of Mount Tambour in 1815 caused the Year Without a Summer. Much larger eruptions, known as large igneous provinces, occur only a few times every hundred million years, but may cause global warming and mass extinctions.
Volcanoes are also part of the extended carbon cycle. Over very long (geological) time periods, they release carbon dioxide from the Earth’s crust and mantle, counteracting the uptake by sedimentary rocks and other geological carbon dioxide sinks. According to the US Geological Survey, however, estimates are that human activities generate more than 130 times the amount of carbon dioxide emitted by volcanoes.
Ocean variability
The ocean is a fundamental part of the climate system. Short-term fluctuations (years to a few decades) such as the El Niño–Southern Oscillation, the Pacific decadal oscillation, the North Atlantic oscillation, and the Arctic oscillation, represent climate variability rather than climate change. On longer time scales, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat by carrying out a very slow and extremely deep movement of water, and the long-term redistribution of heat in the world’s oceans.
Human influences
Anthropogenic factors are human activities that change the environment. In some cases the chain of causality of human influence on the climate is direct and unambiguous (for example, the effects of irrigation on local humidity), while in other instances it is less clear. Various hypotheses for human-induced climate change have been argued for many years. Presently the scientific consensus on climate change is that human activity is very likely the cause for the rapid increase in global average temperatures over the past several decades. Consequently, the debate has largely shifted onto ways to reduce further human impact and to find ways to adapt to change that has already occurred.
Of most concern in these anthropogenic factors is the increase in CO2 levels due to emissions from fossil fuel combustion, followed by aerosols (particulate matter in the atmosphere) and cement manufacture. Other factors, including land use, ozone depletion, animal agriculture and deforestation, are also of concern in the roles they play – both separately and in conjunction with other factors – in affecting climate, microclimate, and measures of climate variables.
Vegetation
A change in the type, distribution and coverage of vegetation may occur given a change in the climate; this much is obvious. In any given scenario, a mild change in climate may result in increased precipitation and warmth, resulting in improved plant growth and the subsequent sequestration of airborne CO2. Larger, faster or more radical changes, however, may well result in vegetation stress, rapid plant loss and desertification in certain circumstances.
Ice cores
Analysis of ice in a core drilled from a ice sheet such as the Antarctic ice sheet, can be used to show a link between temperature and global sea level variations. The air trapped in bubbles in the ice can also reveal the CO2 variations of the atmosphere from the distant past, well before modern environmental influences. The study of these ice cores has been a significant indicator of the changes in CO2 over many millennia, and continues to provide valuable information about the differences between ancient and modern atmospheric conditions.
Sea level change
Global sea level change for much of the last century has generally been estimated using tide gauge measurements collated over long periods of time to give a long-term average. More recently, altimeter measurements — in combination with accurately determined satellite orbits — have provided an improved measurement of global sea level change.
Contributions of Atmospheric Gases and Solar Radiation to Warming:
Scientists have estimated the contribution to warming made by a range of gases, dust and solar radiation. They have a high level of certainty that greenhouse gases contribute the most to warming, with increases in CO2 as the greatest contributor with about 1.4 watts/meter2 and methane, nitrous oxide, and halocarbons making smaller contributions. Scientists have a lower level of certainty about the contributions of reductions in stratospheric ozone and increases in tropospheric aerosols, which cool the Earth by 0.3 watts/meter2 and 0.9 watts/meter2 respectively. Solar radiation may also contribute to warming but scientists have a very low certainty about the level of this contribution.
Global warming is here, it’s human-caused, and it will continue for centuries even if greenhouse-gas emissions are stabilized, an international panel of climate experts said in a report issued today.
The Intergovernmental Panel on Climate Change (IPCC) used its strongest language yet to link human activity to Earth’s warming temperatures, rising seas, more intense storms, and a host of other environmental maladies.
“Fossil fuel use, agriculture, and land-use change are fundamentally affecting the systems on our planet,” Achim Steiner, executive director of the United Nations Environment Programme, said at a press briefing in Paris, France.
(Get the basics: “Global Warming Fast Facts.”)
The United Nations and the World Meteorological Organization oversee the IPCC.
Hundreds of climate experts and government representatives from 113 countries labored all week in Paris to reach unanimous agreement on the wording of each sentence in the 20-page summary for policymakers.
“Most of the observed increase in globally averaged temperature since the mid-20th century is very likely due to the observed increase in anthropogenic [human-caused] greenhouse gas concentrations,” the report reads.
The phrase “very likely” translates to a 90 percent probability, the report’s authors note. This is a significant departure from previous reports.
In 2001 the panel concluded humans were “likely,” or with 66 percent probability, the cause of global warming. The panel also released reports in 1995 and 1990.
“Each time they’ve used a more explicit statement about the human contribution,” said Henry Jacoby, co-director of the Center for Energy and Environmental Policy Research at the Massachusetts Institute of Technology, in a phone interview Thursday.
Jacoby, who studies the threat of global climate change, said the report will cause some people to “be somewhat more concerned” but doubted it would be “revolutionary” in spurring action to reduce greenhouse gas emissions.
During the 20th century global mean surface temperature rose about one degree Fahrenheit (IPCC, Synthesis Report 5). These are just a few climate changes associated with the current global trend towards warming. Ther have been natural cycles of climate change since earth’s formation, however in recent centuries humans have influenced global climate change through the emission of greenhouse gases. While many scientists believe that the current trend of global climate change is going in the direction of warming and their studies show that global warming is a threat to humans, wildlife, and ecosystems. Most scientists and their studies also agree that human actions, especially the burning of oil and fossil fuels, are contributing to global warming, however there is much debate over to what extent human actions are causing global warming. Some scientists and politicians believe that a warming trend is occurring, however, they are convinced that it is still mostly a natural trend. In contrast many scientific studies on climate change show that human actions are definitely a factor in global warming and may be significant whether minor or not, as the human factor even if small could be enough to cause irreversible changes in Earth’s climate and natural climate change cycle. For this reason greenhouse gas emissions by humans need to be reduced in order to limit human’s affect on the climate cycle. It is also important that efforts are undertaken towards being prepared for a forced adaptation to a warmer climate that is likely to occur due to human’s actions in the past several decades.
Global climate change and the current global warming trend affect all living things on our planet, including animals, plants, and humans. Some of the possible consequences of global warming are “heat waves, water shortages, rising sea levels, loss of beaches and marshes,
Many scientific studies have shown that greenhouse gases contribute to global warming. Greenhouse gases are necessary for keeping the planet habitable, however too much can cause the planet to become too warm for human inhabitation. According to the Intergovernmental Panel on Climate Change (IPCC), “most of observed warming over last 50 years [is] likely due to increases in greenhouse gas concentrations due to human activities” (Synthesis Report 31). Evidence from air bubbles in ice core samples has allowed scientists to determine the composition of the atmosphere and infer climatic changes over the past several millennia (IPCC, The Scientific Basis 202). By comparing the past atmosphere composition with the present composition there has been substantial increase in greenhouse gases, “primarily carbon dioxide, methane, and nitrous oxide” (Baird 14), over the last century. The evidence from ice core samples also shows a correlation between past global warming and an increase in greenhouse gases, thus “like today’s global warming, the ancient warming was caused by massive releases of carbon-bearing greenhouse gases” (Curtin 13). In the past the increase in greenhouse gases was due to natural processes such as volcanic eruptions. In contrast, the increase in greenhouse gases since the Industrial Revolution is mostly caused by human actions, such as the burning of fossil fuels and oil, as well as land use changes. While these greenhouse gases are important for trapping some of the sun’s heat and making our planet inhabitable, too much greenhouse gases “could eventually cause the planet to be much less habitable for humans, plants, and animals” (Baird 14). Because some greenhouses gases, such as carbon dioxide, have long lives in the atmosphere, it is important to limit greenhouse gas emissions soon before it is too late, as even with a stabilization of low emissions the effects of greenhouse gases already in our atmosphere will continue to cause global warming for at least another century.
Many scientists believe that the increased emissions of greenhouse gases by humans are a factor in global warming, however they are uncertain to what extent the current trend is a natural climate change process. This uncertainty has been blown out of portion by several politicians, mostly Republicans, as is indicated in the statements collected from them in a 2006 Congressional Insiders Poll about if man is a factor in global warming. One congressman is reported saying that “there is absolutely no conclusive evidence that it has anything to do with man” (Bell 5). Based on results from scientific studies most scientists believe that man does have an a significant role in the current global warming trend and even those that doubt human’s role in the current climate change, such as Richard S. Linden, admit that humans do have an affect on climate, although he believes human’s role to be an extremely small and insignificant factor (Grossman 39). It is this minority of doubters, which appear to have no scientific studies to back up their doubt, that the current United States Presidential Administration uses to back up their belief that global warming is not cause by humans, thus the economic costs of limiting our fossil fuel consumption is unreasonable and refuses to sign the Kyoto Protocol, which sets guidelines for reducing greenhouse gas emissions. Even if actions to limit greenhouse gas emissions suddenly began to occur the human impact of the environment due to the emission of greenhouse gases would remain considerable. According to projections by IPCC in order
for carbon dioxide numbers in the atmosphere to become stabilized there needs to be a global drop in the emission of carbon dioxide by human activities under 1990 levels by the middle of the 21st century for carbon dioxide levels to be stabilized at 450 ppm (parts per million), by the end of the 21st century for stabilization at 650 ppm, and by the end of the 22nd century to be stabilized at 1,000 ppm (IPCC, Synthesis Report 31). Even if the stabilization occurs at 450 ppm “global average surface temperature during [the] 21st century [will continue] rising
Global climate change is an issue that affects our planet’s environment as a whole, including the sea, the atmosphere, animals, and humans. Scientific evidence exists that not only supports that global climate change is occurring and is currently characterized by warming. Studies show that one of the causes of the global warming trend is an increase of greenhouse gases in the earth’s atmosphere, which is related to past climate change events by using Antarctic ice core samples. This increase in greenhouse gases in the past century mostly from human actions, especially the burning of oil and fossil fuels, and only slightly to natural occurrences, such as volcanic eruptions as in the past. While scientists are not certain how much the increase in greenhouse gases contribute to global warming, there is little doubt that it is a contributing factor and a result of human actions. Although further studies are needed to determine how much of the global warming trend is natural, it appears clear that greenhouse gas emissions need to be reduced in order to curb the impact humans have on climate change cycles and humans also need to learn to adapt to the irreversible changes that we may have already caused.
Bangladesh in global warming scenario:
Today one of the most hotly deliberated topics on Earth is the issue of global warming or climate change. Increased populations, extreme demand for energy and limited resources have put the global environment under threat. As a result we are getting increasingly aware about the stake of environment we reside in. Nowadays the terms greenhouse effect, industrial pollution, air pollution, sustainable development, and biodiversity etc. have become frequently used words.
The greenhouse effect is a natural occurrence initiated by carbon dioxide and other gases in the atmosphere. Scientists all over the world have known for more than a century that greenhouse gases like carbon dioxide, methane, water vapour and chlorofluorocarbons help prevent heat from escaping the earth’s atmosphere. In the temperate region green houses are built to cultivate crops when the outer land remains covered by snow. Sun light of a shorter wavelength enters the glass roof of the green house and strikes the soil and radiates back with a longer wave length. The change in wave length of sunlight transports the release of heat energy. This stored heat energy raises the green house temperature, making its environment suitable for crop growth though the outside temperature still remains around freezing point. Similarly, greenhouse gases also keep the earth warm enough to support life. So, the concern is not with the fact that we have a greenhouse effect, but whether human activities are leading to an enhancement of the greenhouse effect or causing the global warming.
Automobiles and other transport exhausts are thought to be the principal source of atmospheric carbon dioxide. Coal or petroleum based power plants and different industries release a huge amount of carbon dioxide into the atmosphere. In addition, animal breathing, plant and microbial respiration, agricultural and other solid waste disposal also produce a large amount of carbon dioxide. This carbon dioxide is dissolved into ocean water, incorporated in marine organism and utilised by green plant and so on.
On the other hand, deforestation may have terrible global effects as well. Forests are natural consumers of carbon dioxide — one of the greenhouse gases whose buildup in the atmosphere contributes to global warming. Annihilation of forest not only removes these carbon sinks, but forest burning and decomposition pump into the atmosphere even more carbon dioxide, along with other greenhouse gases. Increase of carbon dioxide in the lower levels of the atmosphere warm sit-up and global warming obviously takes place. The global climate models predict that a doubling of carbon dioxide concentration will increase the mean daily temperature by about two ( to five degree centigrade. There are likely to be more natural calamities like devastating hurricanes, tornedos, cyclones, storms and drought. Altered weather will greatly harm the world’s largest food source or agricultural pattern.
Indirect indicators of warming such as borehole temperatures, snow cover, and glacier recession data are in significant agreement with the more direct indicators of recent warmth. Evidence such as changes in glacier length is useful since it provides qualitative support for existing meteorological data. However, there is a great deal of disagreement among scientists about whether global warming is actually occurring and it is certainly an important political issue which has shaped legislation and generated regulations.
According to Special Report on Emission Scenarios (SRES) published by Intergovernmental Panel on Climate Change (IPCC), due to thermal expansion and loss of mass from glaciers and ice caps, global mean sea level is projected to rise by 0.09 to 0.88 meters between 1990 and 3100. Over several centuries, it may be possible to observe the effect of these orbital parameters, however for the prediction of climate change in the 21st century, these changes will be far less important than radiative forcing from greenhouse gases. Further research is required to improve the ability to detect, attribute and understand climate change, to reduce uncertainties and to project future climate changes. In particular, there is a need for additional systematic and sustained observations, modeling and process studies.
In the 1970s, various sectors of the scientific community became concerned about the possible reduction in the ozone layer surrounding the earth in the upper atmosphere. After a decade like in 1980s, scientists, governments, and the public in all over the world became concerned about the possibility that the world may be getting warmer. However, there is much need to refine our understanding of key natural forcing mechanisms of the climate, including solar irradiance changes, in order to reduce uncertainty in our projections of future weather pattern change.
As it relates to recent estimate by Intergovernmental Panel on Climate Change (IPCC), due to global warming the sea level may levitate by about 20 centimeter by 2030 and it could be as much as one meter by the end of the next century depending upon the future control of green house gases.
Based on the geographical structure like low elevation of the land areas, the low inclining of the rivers, and proximate to the sea, Bangladesh is one of the most susceptible country to the effects of sea level rise and climate change. In coastal area, the significant effects of sea level changes on flooding, drainage, agriculture, tides, waves and vital wetlands cannot be overlooked. One (1) meter sea level rise will inundate about 5,608 million acres of existing coastal land which is about 15 percent of the total area of Bangladesh. The area comprising of 65 percent of greater Khulna, 99 percent of Barisal, 100 percent of Patuakhali, 44 percent of Noakhali and 12 percent of Faridpur will be inundated and as a result 13.74 percent of net cropped area and about 401,600 hectares of mangrove forest along with its wild life will be vanished.
A very rough appraisal indicates that with one meter sea level rise, area of high salinity intrusion will increase from existing 13 percent to 31 percent of Bangladesh land area. In fact, entire south and south western part of Gages, Padma-Lower and Megna river system will be affected by high salinity penetration. This will reduce the crop yield significantly in the affected areas. Salinity intrusion may affect the power station’s water use in the Siddhirganj and Narayanganj areas.
It is patent that the green house effect is a great threat for the world. The industrialized countries are mostly responsible for this undesirable effect. The use of chlorofluorocarbons in air conditioners, refrigerators, and as propellants has resulted in the release of large amounts into the atmosphere. Because chlorofluorocarbons are implicated in both global warming and ozone depletion, considerable international attention is focused on controlling their manufacture and release.
Cutting across these uses is a crucial need associated with strengthening international co-operation in order to better utilize scientific, computational and observational resources. This should also promote free exchange of data among scientists. A special need is for increasing the observational and research capacities in many regions, particularly in developing countries. Finally, as is the goal of this assessment, there is a continuing imperative to communicate research advances in terms that are relevant to decision making.
Global warming may be reduced by three inter linked levels such as personal, technological and legal. The levels should work by energy conservation, shifting to renewable energy sources, reforestation and educating people to make them aware about global warming. At the personal level, recycling, increasing efficiency and reducing demands for every item are parts of conservation strategy. Use of renewable energy sources like solar and wind energy should be enhanced. Improvement of energy efficiency of all machinery, buildings and factories will reduce the rate of carbon dioxide emission. Replacement of fossil fuels by solar energy, biofuels (ethanol) hydropower, hydrogen fuel, wind etc. will reduce the carbon dioxide emissions.
It is an obvious indication in modern science that we will be living with global warming for the rest of our lives. Thus, it is indispensable to think ahead and take all essential steps in time to minimise the greenhouse emissions all over the world otherwise soon it will be too late. Finally, control of the green house gas is the crying need for maintaining an environmental equilibrium and saving the world for the future generations.
Bangladesh faces tsunami threat:
Michael Casey, AP Environmental Writer
BANGKOK, Thailand — More than 1 million people in South Asia’s Bay of Bengal could be swept to their deaths by a tsunami if a giant earthquake were to hit off the coast of Myanmar, according to a study published Thursday.
But the study’s author, Phil Cummins, said he does not have enough data to say whether such a cataclysmic event — a quake projected to be from 8.5 magnitude to 9.0 magnitude — is likely to hit parts of Myanmar and Bangladesh in the next few decades or in several hundred years. Smaller quakes in the immediate area are rare.
“I don’t want to cause a panic. There is no reason anything like this would happen soon,” said Cummins, of Geoscience Australia, the federal agency that carries out geoscientific research.
The threat of tsunamis has taken on added urgency in recent years after a 9.3-magnitude earthquake off Indonesia’s Sumatra island in December 2004 triggered a tsunami that killed more than 230,000 people and left a half million homeless in a dozen countries. Myanmar and Bangladesh suffered relatively minor damage from the tsunami, with 61 people and 2 people killed, respectively.
Previous research had shown the potential for large quakes in the Bay of Bengal area but Cummins’ said his study, which appears in Thursday’s issue of the journal Nature, is the first to suggest a big quake could spawn a tsunami “that could have pronounced impact on the Chittagong coast and the Ganges-Bhramaputra delta at the northern tip of” the bay.
The numbers of people at risk from a tsunami, Cummins wrote, may be “over a million,” given that the region is home to Bangladesh’s second largest city of Chittagong and there are tens of millions of people living just above sea level in the region.
Cummins has not presented his findings to the governments of Myanmar and Bangladesh. Officials from Myanmar and Bangladesh could not immediately be reached for comment.
The area Cummins studied is a section of the Sunda Megathrust known as the Arakan Subduction Zone where the Indian and Southeast Asia plates meet. The Sunda Megathrust stretches all the way from Western Australia to the Himalayas, and ruptures along that fault line were blamed for the Sumatra earthquake in 2004.
Examining historical records, Cummins found evidence that an earthquake estimated at magnitude 8.5 to 9.0 struck off the western Myanmar coast in April 1762 — the most recent large quake found in the records.
He said it probably produced a tsunami, citing eyewitness accounts of waves washing over nearby Cheduba Island, submerged coasts near Chittagong and causing river levels as far inland as the Bangladeshi capital Dhaka — about 62 miles.He said future quakes and tsunamis were likely, given the historical accounts and more recent surveys of the area, which determined a magnitude 8.5 quake would hit the area every 100 years and a 9.0 every 500 years.
“I would hope this spurs further work in confirming these past events,” he said. “It should be possible to answer how big was this event, how often do these events occur and what kind of tsunamis are generated through further geological investigation.”
He said it was difficult for local authorities to take action to prevent the disaster, since it was not likely an immediate threat and any tsunami would probably inundate threatened regions from within 10 minutes to two hours.
The reaction to Cummins’ findings has been mixed, with some tsunami experts saying they shed important light on a section of Sunda Megathrust that has received little attention in the past.
“The main value of the paper is in advertising the danger of the section of the megathrust that no one has worried about,” said California Institute of Technology’s Kerry Sieh, who has used coral records and GPS networks to predict that a big quake and tsunami are likely to hit parts of SumatraIsland in the coming decades.
“The effects on the west coast of Myanmar and more importantly Bangladesh would be awful,” he said.
But Costas Synolakis, director of the TsunamiResearchCenter at the University of Southern California, insisted he and others presented findings at earlier seminars showing there was a threat of a quake-generated tsunami in the Bay of Bengal but that the worst impact would be in Sri Lanka.
“There is nothing new here,” Synolakis said in an e-mail interview.
Synolakis also said the scenario presented by Cummins “could lead to a massive panic south of Chennai (India) and possibly a sense of reassurance in Sri Lanka,” where he said the threat of another tsunami was worse.
