ozone layer depletion, greenhouse effect & global warming

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This is a presentation regarding some of those little threats our Earth is going through....The presentation is made interesting with a wide range of pictures, illustrations and animations...Please download to see the animated slideshow...Hope this comes of help to you!



Science Presentation Ozone Layer Depletion & Greenhouse effectThe Ozone Layer And Ozone HolesWhat is Ozone? A molecule containing three atoms of oxygen is called ozone. Ozone is very rare in our atmosphere, averaging about three molecules of ozone for every 10 million air molecules. In spite of this small amount, ozone plays a vital role in the atmosphere.

Where is ozone found in the atmosphere? Ozone is mainly found in two regions of the Earth's atmosphere. Most ozone (about 90%) resides in a layer that begins between 6 and 10 miles (10 and 17 kilometers) above the Earth's surface and extends up to about 30 miles (50 kilometers). This region of the atmosphere is called the stratosphere. The ozone in this region is commonly known as the ozone layer.

What is the role of the ozone layer and how are humans affected by it? Ozone present in the stratosphere plays a beneficial role by absorbing most of the biologically damaging ultraviolet sunlight. The absorption of ultraviolet radiation by ozone creates a source of heat. Ozone thus plays a key role in the temperature structure of the Earth's atmosphere. Without the filtering action of the ozone layer, more of the Sun's UV radiation would penetrate the atmosphere and would reach the Earth's surface. Many experimental studies of plants and animals and clinical studies of humans have shown the harmful effects of excessive exposure to UV radiation.

At the Earth's surface, ozone comes into direct contact with life-forms and displays its destructive side (hence, it is often called "bad ozone"). Because ozone reacts strongly with other molecules, high levels of ozone are toxic to living systems. Several studies have documented the harmful effects of ozone on crop production, forest growth, and human health. The substantial negative effects of surface-level ozone present in the troposphere from direct toxicity contrast with the benefits of the additional filtering of UV radiation that it provides.

There is also widespread scientific and public interest and concern about losses of ozone in the stratosphere. Ground-based and satellite instruments have measured decreases in the amount of stratospheric ozone in our atmosphere. Over some parts of Antarctica, up to 60% of the total overhead amount of ozone (known as the column ozone) is depleted during Antarctic spring (September-November). This phenomenon is known as the Antarctic ozone hole. In the Arctic polar regions, similar processes occur that have also led to the depletion of column ozone.

What is the ozone hole? Theozone holeis an annual thinning of theozone layeroverAntarctica. The most pronounced decrease in ozone has been in the lowerstratosphere. However, the ozone hole is most usually measured not in terms of ozone concentrations at these levels (which are typically of a few parts per million) but by reduction in the totalcolumn ozone.

The Antarctic Ozone Hole

The Ozone hole as seen from the EarthWhat causes Ozone Holes? The cause of the ozone holes is generally agreed to beCFC(chlorofluorocarbon) compounds which break down due toultravioletlight and becomefree radicalscontaining chlorine high in the Earth's atmosphere. These radicals then break down the ozone catalytically. The ozone layer can also be depleted by free radical catalysts, includingnitric oxide(NO),nitrous oxide(N2O),hydroxyl(OH), atomicchlorine(Cl), and atomicbromine(Br). 15

What are CFCs ? Achlorofluorocarbon(CFC) is anorganic compoundthat contains onlycarbon,chlorine, andfluorine, produced as avolatilederivative ofmethaneandethane. Chlorofluorocarbons (CFCs) are anthropogenic compounds that have been released into the atmosphere since the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and as solvents.

What actions have been taken to protect the ozone layer? Through an international agreement known as the Montreal Protocol on Substances that Deplete the Ozone Layer, governments have decided to eventually discontinue production of CFCs, halons, carbon tetrachloride, and methyl chloroform (except for a few special uses), and industry has developed more "ozone-friendly" substitutes. All other things being equal, and with adherence to the international agreements, the ozone layer is expected to recover over the next 50 years or so.

The Greenhouse Effect

Greenhouse GasesGreenhouse gases are those gases in the atmosphere that absorbs and emits radiations within a thermal infra-red range. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. The Greenhouse EffectThe greenhouse effect is the process in which greenhouse gases absorbs radiation (the infra red rays) and re- radiates it in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.


CO2CO2CO2co2CO228Why is this effect named after a greenhouse?A greenhouse is a structural building with different types of covering materials, such as a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible sunshine is absorbed inside the structure. Air warmed by the heat from warmed interior surfaces is retained in the building by the roof and wall; the air that is warmed near the ground is prevented from rising indefinitely and flowing away. This process in which the heat is trapped within the greenhouse can be compared to the way in which the heat radiations are trapped in the earths atmosphere.

how to reduce greenhouse effect?Green house effect is something that cannot be prevented but can be reduced. It can be reduced in the following ways:By opting for greener technologies that are eco-friendly. By reducing emissions from automobiles, the greenhouse gases can be reduced. By preventing deforestation, because plants absorb a great amount of CO2 from the atmosphere. By using CFC-free refrigerators.By reducing use of aerosols because they produce CFCs.

Global Warming Global warming refers to an unequivocal and continuing rise in the average temperature of Earth's climate system. Most of global warming is being caused by increasing concentrations of greenhouse gases produced by human activities. Future climate change and associated impacts caused by global warming will vary from region to region around the globe. Global warming can be prevented by reducing the emission of greenhouse gases.Effects of Global WarmingIncrease in spread of disease.Warmer waters and more hurricanes.Increase in droughts and heat waves.Economic consequences.Melting of polar ice caps.Floods.Fires and wildfires.Storms.Death by smog.Desertification.Tsunamis.Cold waves.Increase in volcanic activities.Loss of biodiversity and animal extinction.

Melting and breaking down of polar ice caps.

Artists illusion of New York city underwater.

Artists illusion of backwards evolution in case of polar bears.Thats all Folks!!


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