Environmental Science Std.-9 Chp.7 Atmosphere and Climate

Transcription

1 Environmental Science Std.-9 Chp.7 Atmosphere and Climate Q.1. Name the layers of the atmosphere. Troposphere Stratosphere Mesosphere Thermosphere Exosphere GREENHOUSE EARTH: Q.2. (a) What is the Greenhouse Effect? It is a natural process that warms the Earth s surface by absorbing the Sun s energy and by re-radiation by greenhouse gases. Some of the sun s energy is reflected to the space and the absorbed energy warms the surface of the Earth. This process makes life possible on Earth by maintaining the Earth s temperature at 33 C. (b) Which are the greenhouse gases responsible for this? Carbon dioxide Water Vapour Methane Nitrous oxide Ozone Chlorofluorocarbons(CFCs) ( 1 )

2 (c) Why is the level of carbon dioxide rising in the atmosphere? Human activities particularly like burning fossil fuels (coal, oil and natural gas), agriculture and land clearing are increasing the concentration of GHGs specially carbon dioxide. (d) How does the increased level of GHGs affecting the temperature of the earth? The increased level of GHGs including carbon dioxide leads to enhance green house effect as these gases trap heat. This in turn, is contributing to Global warming. Q.3. Mention the causes for global warming. (Any 3) Burning of fossil fuels Deforestation Industrial waste and landfills Q.4. How does deforestation lead to global warming? Forests are called natural Carbon Sinks as they take in carbon dioxide from the atmosphere to be used in the process of photosynthesis. Large developmental activities have led to the indiscriminate cutting down of trees and this is what is leading to global warming. Global Warming and its effects: Q.5. What is global warming? The increased level of GHGs, such as carbon dioxide emissions from burning fossil fuels, Deforestation trap heat that would otherwise escape from Earth. This is changing the Earth s climate permanently. Q.6. What are the effects of global warming on weather? 1. Frequent heat waves. Unnatural hot weather has become common in recent years. Intense heat waves are more frequent. This may lead to heat stroke, exhaustion and aggravation of existing health problems. 2. Heavier precipitation and flooding Q.7. How is global warming affecting the sea level in the world? Global warming is accelerating the rate of sea level rise, increasing flooding risk in low lying areas and high-risk to coastal properties. Q.8. Explain the effect of Global Warming on agriculture. Global warming is leading to rise in temperature, heavy rainfall and severe droughts. Agricultural output will suffer due to this and this may lead to food shortage. ( 2 )

3 THE OZONE LAYER: Q.9. Define Ozonosphere. Ozonosphere or the Ozone layer is a region of the upper atmosphere containing a very high concentration of ozone molecules. Q.10. How are the ozone molecules distributed in the Troposphere and Stratosphere? 90% (0-9/17km) of the ozone in the atmosphere is present in the stratosphere. Remaining 10% (17-50km) of ozone is present in the troposphere. Q.11. Why is the Ozone layer important? The ozone layer blocks almost all the solar radiations of wavelengths less than 290 nanometers from reaching the earth s surface. The Ultraviolet rays which are harmful to most living things is absorbed by this layer. Q.12. How was the damage to the ozone layer detected? It was detected by the presence of an ozone hole over Antarctica. The ozone hole was disc overed by Farman, Gardiner and Shanklin. NASA scientists re-analyzed their satellite data and found that the whole of Antarctic was affected. ( 3 )

4 The below given picture gives an idea about the increasing size of Ozone hole. Q.13. What is the reason for the depletion of the ozone layer? Scientific evidence indicates that stratospheric ozone is depleted by a group of manufactured chemicals containing chlorine and/or bromine. These chemicals are called ozone depleting substances (ODS). Q.14. How do the ODS deplete the ozone? ODS are very stable, nontoxic and environmentally safe in the lower atmosphere. Their very stability allows them to float up to the stratosphere. Once they reach stratosphere, they are broken apart by intense UV light, releasing Chlorine and Bromine. Chlorine and Bromine deplete ozone at an alarming rate, by stripping an atom from the ozone molecule. ODS also have a long lifespan in the atmosphere say up to several centuries. Hence,ODS released over the last 80 years are still adding up to ozone depletion. Q.15. Mention some important ODS. Chloroflurocarbons(CFCs) Halons Methyl Chloroform Carbon tetrachloride Hydrofluorocarbons(HCFCs) ( 4 )

5 Q.16. What are the sources of the various ODS? CFCs Refrigerators/Freezers/ACs/Solvents/Hospital sterilants/foam products Halons Fire extinguishers Methyl Chloroform Aerosols/Adhesives/Chemical Processing Carbon Tetrachloride Solvents/ Fire Extinguishers Q.17. What is ozone hole? It is a region of marked thinning of the ozone layer in high latitudes, mainly in winter, Due to the chemical action of CFCs and other atmospheric ODS. Q.18. Mention the effects of depletion of ozone layer. Harm to human health UV rays can cause skin cancer/sunburn and premature aging of skin/ cataracts/blindness etc Adverse effect on agriculture, forestry and natural ecosystems. Major crop species are Vulnerable to increased UV rays. This may lead to reduced growth, photosynthesis and flowering. Damage to marine life. Plankton, the first vital link in aquatic food chain are threatened by increased UV radiation. This leads to disruption of fresh & salt water food chains. Materials. Wood, plastic, rubber, fabrics are degraded by UV radiation. The economic impact of replacing and protecting materials could be significant. Q.19. What is Montreal Protocol? The Montreal Protocol on substances that deplete the ozone layer is an international treaty Designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. ODS controlled by Montreal Protocol includes CFCs, Halon, HCFCs, Methyl Chloroform, Methyl Bromide etc ( 5 )