Global Warming - Global Warming Is it really an...

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Global Warming Is it really an inconvenient truth? A gadfly’s report by tom bush
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05/07/09 Friday Seminar/tob 2 Human Impact on Global Climate Humans have been modifying environment over extensive areas for thousands of years fossil fuels overgrazing of marginal lands killing off the native animals building cities So do animals and plants
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05/07/09 Friday Seminar/tob 3 Surface Temperature Reconstruction for the last 2000 years National Academy of Sciences Chaired by Gerald R. North Distinguished Professor Department of Atmospheric Sciences Study Concluded Northern hemisphere was warmer during the late 20 th century than any other time during the past millennium Presented to 109 th Congress
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05/07/09 Friday Seminar/tob 4 Five key Conclusions 1. Instruments measured warming of about 1 0 F (0.55 0 C) during the 20 th Century. 2. Large scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium including the relative warm period the “Medieval Warm Period” and a relatively cold period the “Little Ice Age” 3. With a high level of confidence the global mean surface temperature was higher during the last few decades of the 20 th century than any comparable period during the last four centuries. 4. …individual locations were higher during the past 25 years than during any period of comparable length since A. D. 900. 5. Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about 900 A. D.
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05/07/09 Friday Seminar/tob 5 Report Summary Statements “Reconstruction of surface temperatures do not tell us why the climate is changing. To answer that question, one would need to examine the factors, or forcings, that influence the climate system.
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05/07/09 Friday Seminar/tob 6
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05/07/09 Friday Seminar/tob 7 Just a Minute - Where Does Temperature Data Come From? Climatologists use many sources Meteorological Instrument records Only about 200 years old Mostly Europe and North America continents ocean data sparse Worldwide satellite data since 1970’s Written documentation and descriptive accounts What people felt – Bitter cold – Heavy snowfall Floods Crop failures, etc
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05/07/09 Friday Seminar/tob 8 More Temperature Sources Proxy data Fossil evidence Tree rings Insect and pollen frequencies in sediments Moraines and glacial deposits Isotope ratios of various elements
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05/07/09 Friday Seminar/tob 9 Climatologists Observations During most of earth’s history Global temperatures were 8 0 to 15 0 Celsius warmer than today Climate is continuously changing
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05/07/09 Friday Seminar/tob 10 What About the Oceans? “Is the World Ocean Warming? Upper –
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Global Warming - Global Warming Is it really an...

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