global warming


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INTRODUCTION ● 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 during the 20th century. ● Most of the observed temperature increase since the middle of the 20th century has been caused by increasing concentrations of greenhouse gases, which result from human activity such as the burning of fossil fuel and deforestation. ● 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 during the 21st century

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EVIDENCES FOR GLOBAL WARMING Earths mountain glaciers are melting, Antarctica’s ice sheets are breaking up, Sea level is rising, Temperature of the global ocean is rising, Northern hemisphere permafrost is melting, Arctic pack is thinning and retreating, tree line in mountain ranges is moving upward, Many tropical diseases are spreading toward poles and higher elevation in the tropics Greenland Largely Ice Free ice sheets breaking up

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DEBATES ON GLOBAL WARMING Debate on the existence of global warming: ● On the basis of instrumental records, simulation models, most scientists claim that global warming is a unique event over last 100 years and it will continue in the foreseeable future. ● Another group claims that simulation and climatic models are not sufficient enough to account for the phenomenon because model cannot take all the possible variables associated with air temperature change and rather counter argues that global warming is temporary rise in the average air temperature which will naturally correct itself over the time like the past.

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B) Debate on the causes of global warming: ● Supporters of global warming theory, recognize global warming as a result of enhanced green house effect on the earth’s surface triggered by anthropogenic activities like combustion of fossil fuels, deforestation etc. ● But the critics dismiss connection between the global warming and human activities and they opine that it is a natural phenomenon triggered by solar variation. combustion of fossil fuels

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C) Debate on the consequences of global warming: The predictions of the precise impacts of global warming on physical and biological processes are again questioned by the critics on the basis of its soundness of climatic models on which predictions are based. El Niño Becomes Permanent

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D) Political debate on the mitigation measures of global warming: If it is taken that global warming is human induced and should be avoided, international agreements like Kyoto protocol, carbon trading and techniques like carbon sequestration becomes necessary to cut green house emission. There is going on blame game between industrial and non-industrial nations to cut their green house emission. Conversely if global warming is taken as natural and beyond human limit, there is no need for such international agreements. GHG emission per capita 2000.

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CRITIQUE OF THE DEBATES ● Temperature records e.g. the 20th century was the warmest century in the last millennium, the 1990s was the warmest decade of the century and 1998 was the warmest year and above mentioned evidences clearly indicate that global warming is a phenomenon and not a myth. But the rate of rise in temperature of the earth in future is disputable. ● The 20th century global warming approximately 0.5 degree Celsius which appears to exceed natural trends (estimated from statistical modelling) of 0.3 degree Celsius per one hundred years

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● It is now widely considered likely that this global warming is very much in harmony with increasing green house gas concentration rather than with other forcing mechanisms such as solar variation but casual linkage is not yet definitely established ● As the present day global warming is mostly anthropogenic in nature, the rate of rise in temperature can be minimized if there is a shift toward renewable and nuclear energy immediately which has been indicated by the IPCC models. ● Finally the arguments and counterarguments in the above debates have led to many research works recently on global warming which will open up some unknown facts about this complex phenomenon to understand it on a more sound basis.

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References Barry, R. G. and Chorley, R. J. (1998) Atmosphere Weather and Climate pp. 325-357, 7th Edition, Routledge, London and New York Crithchfield, H. J. (2004) General Climatology pp. 227-245,4th Edition Prentice-Hall of India private Limited, New Delhi-110001 http:// Lamb, H.H. (1977) The changing Climate: selected papers, pp.236, Methuen, London Lutgens, F. K. and Tarbuck, E. J. (2001) The Atmosphere- An Introduction to Meteorology,pp. 368-388, 8th Edition, Prentice Hall, Upper Saddle River, New Jersey 07458 Oliver, J. E. and Hidore, J. J. (2003) Climatology -An Atmospheric Science, pp. 296- 309,2nd Edition, Pearson Education Pearce, Fred, 2007, With Speed and Violence: Why Scientists Fear Tipping Points in Climate Change, pp.8, 78, 90-98, Beacon Press, Boston Singh, S. (2005) Climatology, pp.372-410,1st Edition, Prayag Pustak Bhawan, Allahadad- 211002, India Wang, J. and Michael,O. 2005. “The Latest Myths and Facts on Global Warming.” Envronmental Defense, [PDF]

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