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Old Tuesday, November 24, 2009
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Default 1.Global warming,2.Green house effect and 3.ozone depletion

Above the three topics have effects on the same path.
How would you explain it?
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first of all u should write the scientific reasons behind these phenomena. then u shud move to the effects of these phenomena which wud be same for all three of them. then write paragraph to describe the similarities.
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Originally Posted by y.rahman View Post
then u shud move to the effects of these phenomena which wud be same for all three of them.
effects due to ozone depletion are because of ultra violet radiation hitting living beings and will be different from effects due to global warming which will act via disturbance in earths climatic conditions
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Post Read this!!

Earth's Protection Shield is Being Destroyed - Ozone Depletion and Global Warming

Stratospheric Ozone
The Earth's atmosphere is made up of different layers. The layer closest to the surface is called the troposphere which extends from the Earth's surface up to about 10 kilometers. The ozone layer is located above the troposphere in the stratosphere (10 km to about 50 km high). Stratospheric ozone is Earth's natural protection for all life forms, shielding our planet from harmful ultraviolet-B (UV-B) radiation. UV-B radiation is harmful to humans, animals, and plant life. The ozone layer is being destroyed by certain industrial chemicals including ozone depleting refrigerants, halons, and methyl bromide, a deadly pesticide used on crops.

Colder Temperatures Increase Ozone Damage
Ozone depletion damage gets much worse when the stratosphere is very cold. This has been the case the past two years, causing extensive ozone depletion. This past winter, ozone depletion reached the most severe levels ever recorded over the Northern Hemisphere. Western United States ozone levels also continue to drop 3-4 percent per decade. Even if all of our efforts to stop harmful emissions are successful, the ozone layer is not expected to begin recovery until around 2020 at the earliest.
Montreal Protocol
Under the auspices of United Nations Environment Programme (UNEP), Governments of the world, including the United States have cooperatively taken action to stop ozone depletion with the "The Montreal Protocol on Substances that Deplete the Ozone Layer", signed in 1987.
Global Warming

The terms, global warming and climate change are often used interchangeably. Gases such as carbon dioxide, methane, nitrous oxide, and refrigerants create a greenhouse effect by trapping heat in the lower atmosphere. This makes the Earth warmer because the sun's rays are allowed into the lower atmosphere but the heat from these rays isn't able to escape.

Global Warming has been Verified
In 1995, 2,500 scientists prepared a report called the Second Assessment of the Intergovernmental Panel on Climate Change (IPCC). The IPCC reports that global warming and climate change is a reality, and that human emissions of greenhouse cases are a culprit. There are several harmful impacts that result from a global warming trend. Impacts from global warming include sea level rise, more extreme weather events including heat waves, frosts, droughts, storms, extinction of species, loss of entire forests, marine life destructionand glacial retreat.
Earth's Temperature is Rising
1998 was the hottest year since accurate records began in the 1840s, and 10 of the hottest years have occurred during the last 15 years. By examining growth rings from trees and ice cores drilled in Antarctica, scientists have determined that the past decade was the warmest in more than four centuries, and that the current rate of warming is probably unprecedented in at least 10,000 years.

The damage to our environment has already started. For example, sea level has risen from 10-25 centimeters and will continue to rise for centuries even if we stop all global warming emissions immediately. As the world warms, the outlook for all life forms looks bleak, unless we can turn down the heat by reducing concentrations of greenhouse gases in the atmosphere.
Kyoto Protocol
The United Nations has developed a framework the "Kyoto Protocol on Climate Change", signed in 1997 convention on global warming and climate change. The adoption of the Kyoto protocol strengthens the framework with new policies and measures including quantified limitation and reduction objectives to greenhouse gas emissions not covered by the Montreal Protocol.
Global Warming Can Increase Ozone Depletion
Scientist's are concerned that continued global warming will accelerate ozone destruction and increase stratospheric ozone depletion. Ozone depletion gets worse when the stratosphere (where the ozone layer is), becomes colder. Because global warming traps heat in the troposphere, less heat reaches the stratosphere which will make it colder. Greenhouse gases act like a blanket for the troposphere and make the stratosphere colder. In other words, global warming can make ozone depletion much worse right when it is supposed to begin its recovery during the next century.
Effects of Ozone Depletion and Global Warming
(UV-B) radiation causes skin cancer, cataracts and immune suppression in both animals and humans. UV-B also damages plants including hardwood forests, and phytoplankton (an alga is a type of phytoplankton which is the building block of the oceanic food chain).
Effect on Infectious Diseases
Most infectious diseases are transmitted by insects and rodents. Transmitters of disease are called vectors. For example, mosquitoes transmit malaria, dengue and viral encephalitis (inflammation of the brain). Like other animals and plants, vectors are accustomed to certain climate conditions. If the climate becomes warmer, the mosquito will try to fly to new places where it can survive and expose more people to the disease. Changes in sea surface temperature and sea level can lead to higher incidence of water-borne infectious and toxin-related illnesses such as malaria (severe chills and fever), cholera (intestinal disease), dengue (characterized by severe pains in the joints and back), and leishmaniasis (skin ulcers).
Human susceptibility to infections can be further compounded by malnutrition. UV-B radiation from ozone depletion damages both plants and animals. UV-B harms amphibian eggs, midge larvae and trout. Crops that are damaged will reduce food availability. UV-B also can damage mammalian immune systems which makes humans and other animals more susceptible to infectious diseases.
Approximately 92 million people are expected to become refugees from global warming and climate change by 2100, not including any added from population growth.
Effects on Earth's Food Chain
Ozone depletion and global warming have harmful effects on plants and animals. If allowed to continue, our food chain will be seriously disrupted. For example, phytoplantkton are tiny floating algae in the ocean which are the base of the marine food chain. In Antarctica, there has been upwards of 50 percent ozone depletion. This means that an unusually high amount of UV-B radiation has reached the Earth's surface in the Antarctic region. UV-B harms the productivity of phytoplankton, thereby reducing the available food for animals that feed on phytoplankton. Krill eat phytoplankton and penguins eat krill. From a climate change perspective, phytoplankton normally absorb a lot of carbon from the air. As phytoplankton dies from UV-B radiation, this carbon is no longer absorbed. This means that more carbon will be left in the atmosphere, contributing to more global warming. More global warming can increase ozone depletion, which kills more phytoplankton, and the process repeats itself.
"Total Environmental Impact" of Refrigerants
Six parameters define the "total environmental impact" of refrigerants on our environment.
  • Ozone Depletion Potential (ODP)
  • Global Warming Potential (GWP)
  • Atmospheric Life
  • Energy Use
  • Equipment Emission Rate
  • Refrigerant Charge

Approximately 70 percent of the world's electricity is generated by the burning of fossil fuels. For every additional kWh used, there are more greenhouse gas emissions generated by electric utility power plants. This is the indirect effect of global warming refrigerants. The environmental impact of even small changes in chiller energy use has an impact. There is a need to use refrigerants that minimize both ODP and GWP to address global environmental concerns. If the efficiency of every centrifugal chiller in the world were increased by only 0.08 kW/ton, power plant-generated greenhouse gas emissions would be reduced by literally billions of pounds. This is an amount equal to removing nearly two million cars from the road each year, or to planting nearly a half billion trees every year.
Action Plan For Organizations Using Refrigerants
Most refrigerants used in air conditioning and refrigeration contribute to global warming in addition to ozone depletion. Even the new non-ozone depleting alternative refrigerants add to the global warming problem. Businesses and organizations using refrigerants are encouraged to take action now to do what's right for both their organization and for the environment. Persons responsible for HVAC and/or environmental concerns in their company or organization need to take strong, immediate actions to reduce ozone depletion and global warming.
Minimize emissions of ozone depleting (ODP) and direct global warming (GWP) refrigerants used by your organization. The most effective way to start reducing emissions is to implement a Refrigerant Management Plan and insure that your organization is complying with EPA's Section 608 Refrigerant Recycling Regulations. Refrigerants should be handled as a controlled substance. A defined leak management program, including leak monitoring and leak repair policies is essential. Provide Refrigerant Management and Regulations Compliance Training to your responsible employees. Organization's using refrigerants should review and implement industry best practices in refrigerant management to minimize emissions at every stage of refrigerant handling. Implement a process to keep current with regulatory changes to insure going compliance requirements are met.
Reduce energy consumption of HVAC systems using refrigerants to reduce indirect global warming emissions. Conduct a building tune-up to reduce your heating, cooling, and electrical loads, and thus your overall energy consumption.
Replace older HVAC systems containing high ozone depleting and/or global warming refrigerants with newer, more efficient systems. Frequently, HVAC systems are oversized. Thus, you may want to consider right-sizing your existing system with a smaller, more energy-efficient one that matches the newly reduced loads. The operating costs of a high efficiency system may offer an attractive pay back of your investment. Evaluate HVAC systems on a total cost of ownership basis, rather than first cost.

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Post Greenhouse Effect!!

Asslamulaikum,
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I can't fix and make it visible help!!
The Greenhouse Effect
The greenhouse effect is a naturally occurring process that aids in heating the Earth's surface and atmosphere. It results from the fact that certain atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the energy balance of the planet by absorbing longwave radiation emitted from the Earth's surface. Without the greenhouse effect life on this planet would probably not exist as the average temperature of the Earth would be a chilly -18° Celsius, rather than the present 15° Celsius.
As energy from the Sun passes through the atmosphere a number of things take place (see Figure 7h-1). A portion of the energy (26% globally) is reflected or scattered back to space by clouds and other atmospheric particles. About 19% of the energy available is absorbed by clouds, gases (like ozone), and particles in the atmosphere. Of the remaining 55% of the solar energy passing through the Earth's atmosphere, 4% is reflected from the surface back to space. On average, about 51% of the Sun's radiation reaches the surface. This energy is then used in a number of processes, including the heating of the ground surface; the melting of ice and snow and the evaporation of water; and plant photosynthesis.

The heating of the ground by sunlight causes the Earth's surface to become a radiator of energy in the longwave band (sometimes called infrared radiation). This emission of energy is generally directed to space (see Figure 7h-2). However, only a small portion of this energy actually makes it back to space. The majority of the outgoing infrared radiation is absorbed by the greenhouse gases (see Figure 7h-3 below).


Figure 7h-3: Annual (1987) quantity of outgoing longwave radiation absorbed in the atmosphere.
(Image created by the CoVis Greenhouse Effect Visualizer).

Absorption of longwave radiation by the atmosphere causes additional heat energy to be added to the Earth's atmospheric system. The now warmer atmospheric greenhouse gas molecules begin radiating longwave energy in all directions. Over 90% of this emission of longwave energy is directed back to the Earth's surface where it once again is absorbed by the surface. The heating of the ground by the longwave radiation causes the ground surface to once again radiate, repeating the cycle described above, again and again, until no more longwave is available for absorption.
The amount of heat energy added to the atmosphere by the greenhouse effect is controlled by the concentration of greenhouse gases in the Earth's atmosphere. All of the major greenhouse gases have increased in concentration since the beginning of the Industrial Revolution (about 1700 AD). As a result of these higher concentrations, scientists predict that the greenhouse effect will be enhanced and the Earth's climate will become warmer. Predicting the amount of warming is accomplished by computer modeling. Computer models suggest that a doubling of the concentration of the main greenhouse gas, carbon dioxide, may raise the average global temperature between 1 and 3° Celsius. However, the numeric equations of computer models do not accurately simulate the effects of a number of possible negative feedbacks. For example, many of the models cannot properly simulate the negative effects that increased cloud cover would have on the radiation balance of a warmer Earth. Increasing the Earth's temperature would cause the oceans to evaporate greater amounts of water, causing the atmosphere to become cloudier. These extra clouds would then reflect a greater proportion of the Sun's energy back to space reducing the amount of solar radiation absorbed by the atmosphere and the Earth's surface. With less solar energy being absorbed at the surface, the effects of an enhanced greenhouse effect may be counteracted.
A number of gases are involved in the human caused enhancement of the greenhouse effect (see Table 7h-1 below). These gases include: carbon dioxide (CO2); methane (CH4); nitrous oxide (N2O); chlorofluorocarbons (CFxClx); andtropospheric ozone (O3). Of these gases, the single most important gas is carbon dioxide which accounts for about 55% of the change in the intensity of the Earth's greenhouse effect. The contributions of the other gases are 25% forchlorofluorocarbons, 15% for methane, and 5% for nitrous oxide. Ozone's contribution to the enhancement of greenhouse effect is still yet to be quantified.

Average concentrations of atmospheric carbon dioxide in the year 2005 were about 380 parts per million (see Figure 7a-1). Prior to 1700, levels ofcarbon dioxide were about 280 parts per million. This increase in carbon dioxide in the atmosphere is primarily due to the activities of humans. Beginning in 1700, societal changes brought about by theIndustrial Revolution increased the amount of carbon dioxide entering the atmosphere. The major sources of this gas include fossil fuel combustion for industry, transportation, space heating, electricity generation and cooking; and vegetation changes in natural prairie, woodland, and forested ecosystems. Emissions from fossil fuel combustion account for about 65% of the extra carbon dioxide now found in our atmosphere. The remaining 35% is derived from deforestation and the conversion of prairie, woodland, and forested ecosystems primarily into agricultural systems. Natural ecosystems can hold 20 to 100 times more carbon dioxide per unit area than agricultural systems.

Artificially created chlorofluorocarbons are the strongest greenhouse gas per molecule. However, low concentrations in the atmosphere reduce their overall importance in the enhancement of the greenhouse effect. Current measurements in the atmosphere indicate that the concentration of these chemicals may soon begin declining because of reduced emissions. Reports of the development of ozone holes over the North and South Poles and a general decline in global stratospheric ozone levels over the last two decades has caused many nations to cutback on their production and use of these chemicals. In 1987, the signing of the Montreal Protocol agreement by forty-six nations established an immediate timetable for the global reduction of chlorofluorocarbons production and use.

Since 1750, methane concentrations in the atmosphere have increased by more than 150%. The primary sources for the additional methane added to the atmosphere (in order of importance) are rice cultivation, domestic grazing animals, termites, landfills, coal mining, and oil and gas extraction. Anaerobic conditions associated with rice paddy flooding results in the formation of methane gas. However, an accurate estimate of how much methane is being produced from rice paddies has been difficult to obtain. More than 60% of all rice paddies are found in India and China where scientific data concerning emission rates are unavailable. Nevertheless, scientists believe that the contribution of rice paddies is large because this form of crop production has more than doubled since 1950. Grazing animals release methane to the environment as a result of herbaceous digestion. Some researchers believe the addition of methane from this source has more than quadrupled over the last century. Termites also release methane through similar processes. Land-use change in the tropics, due to deforestation, ranching, and farming, may be causing termite numbers to expand. If this assumption is correct, the contribution from these insects may be important. Methane is also released from landfills, coal mines, and gas and oil drilling. Landfills produce methane as organic wastes decompose over time. Coal, oil, and natural gas deposits release methane to the atmosphere when these deposits are excavated or drilled.

The average concentration of nitrous oxide in the atmosphere is now increasing at a rate of 0.2 to 0.3% per year. Sources for this increase include land-use conversion; fossil fuel combustion; biomass burning; and soil fertilization. Most of the nitrous oxide added to the atmosphere each year comes from deforestation and the conversion of forest, savanna and grassland ecosystems into agricultural fields and rangeland. Both of these processes reduce the amount of nitrogen stored in living vegetation and soil through the decomposition of organic matter. Nitrous oxide is also released into the atmosphere when fossil fuels and biomass are burned. However, the combined contribution of these sources to the increase of this gas in the atmosphere is thought to be minor. The use of nitrate and ammonium fertilizers to enhance plant growth is another source of nitrous oxide. Accurate measurements of how much nitrous oxide is being released from fertilization have been difficult to obtain. Estimates suggest that the contribution from this source may represent from 50% to 0.2% of nitrous oxide added to the atmosphere annually.

Ozone's role in the enhancement of the greenhouse effect has been difficult to determine scientifically. Accurate measurements of past long-term (more than 25 years in the past) levels of this gas in the atmosphere are currently unavailable. Concentrations of ozone gas are found in two different regions of the Earth's atmosphere. The majority of the ozone (about 97%) found in the atmosphere is localized in the stratosphere at an altitude of 15 to 55 kilometers above the Earth's surface. In recent years, the concentration of the stratospheric ozone has been decreasing because of the buildup of chlorofluorocarbons in the atmosphere (see Lecture 7e). Since the late 1970s, scientists have discovered that total column ozone amounts over Antarctica in the springtime have decreased by as much as 70%. Satellite measurements have indicated that the zone from 65° North to 65° South latitude has had a 3% decrease in stratospheric ozone since 1978. Ozone is also highly concentrated at the Earth's surface. Most of this ozone is created as an artificial by product of photochemical smog.

In summary, the greenhouse effect causes the atmosphere to trap more heat energy at the Earth's surface and within the atmosphere by absorbing and re-emitting longwave energy. Of the longwave energy emitted back to space, 90% is intercepted and absorbed by greenhouse gases. Without the greenhouse effect the Earth's average global temperature would be -18° Celsius, rather than the present 15° Celsius. In the last few centuries, the activities of humans have directly or indirectly caused the concentration of the major greenhouse gases to increase. Scientists predict that this increase mayenhance the greenhouse effect making the planet warmer. Some experts estimate that the Earth's average global temperature has already increased by 0.3 to 0.6° Celsius, since the beginning of this century, because of this enhancement. Predictions of future climates indicate that by the middle of the next century the Earth's global temperature may be 1 to 3° Celsius higher than today.
Table 7h-1: Gases involved in the Greenhouse Effect: past and present concentration and sources.

Greenhouse Gas
Concentration
1750
Concentration
2003
Percent Change
Natural and Anthropogenic Sources
Carbon Dioxide280 ppm376 ppm34%Organic decay; Forest fires; Volcanoes; Burning fossil fuels; Deforestation; Land-use changeMethane0.71 ppm1.79 ppm152%Wetlands; Organic decay; Termites; Natural gas & oil extraction; Biomass burning; Rice cultivation; Cattle; Refuse landfillsNitrous Oxide270 ppb319 ppb18%Forests; Grasslands; Oceans; Soils; Soil cultivation; Fertilizers; Biomass burning; Burning of fossil fuelsChlorofluorocarbons (CFCs)0880 pptNot ApplicableRefrigerators; Aerosol spray propellants; Cleaning solventsOzoneUnknownVaries with latitude and altitude in the atmosphereGlobal levels have generally decreased in the stratosphere and increased near the Earth's surfaceCreated naturally by the action of sunlight on molecular oxygen and artificially through photochemical smog production
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