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Lecture 2

Week 9 Lecture 2 GEOG 2200 2012 Notes.docx

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GEOG 2200
John Milton

Page1Week 9 Lecture 2 Climate Change and UsGEOG 2200 2012How do we see natural disaster and climate change Certainly Hollywood has presented us with a diverse collection of disaster movies and more recently movies inspired by climate changeLast Tuesday I ended with a short video about the climate change debate Where do you see yourselves as individuals How many of you think that it is too latethat climate change is coming whether we adjust our habits right now Should we looking at mediation as opposed to avoidanceClimate Change through TimePlace matters when it come to climateand will be even more important when it comes to changes in our climate Our understanding of climate is very limited We live in an interglacial periodthe Holocene Epoch or Interglacial Period Before the Holocene Interglacial was the frigid Pleistocenethe last ice age when all of Canada was covered by the Wisconsinan glaciers The severity of the late Pleistocene period was enhanced by the explosion of Toba in presentday Indonesia This volcano didnt just eruptit exploded like Tambora in 1815 sending millions of tons of debris into the upper atmosphere obscuring the sun and sending the Earth into an even deeper cold The crater of Toba remainsabout 90 kilometres long and 50 kilometres wide The warming of the planet began about 18000 years before present BP and we remain in this interglacial period today This isnt the first such interglacial period About 140000 years ago the earlier interglacial period the Eemian Interglacial It came to an end with the advancement of glaciers ice sheets and ultimately the planets weather turned colder and ultimately triggered the Pleistocene glacial period But 18000 years ago humans existed Humans witnessed the dramatic change in climate that brought us out of a glacial period and into this interglacial warm periodThese oscillations in our climate as highlighted last Tuesday can be influenced by celestial and terrestrial factors The warmth that the Earth receives from the Sun varies according to the position of the Earth as well as the longrange cycles of the Sun itself There is a documented 11year Sunspot cycle but this does not correlate to changes in climate However longer fluctuations in the Suns strength are simply not understoodThen there is the orbit of the Earth This is not steady or fixed An eccentricity in our orbit takes the Earth farther and nearer to the Sun in a cycle of more than 400000 years The inclination of that orbit also changes in a cycle ranging from 100000 to 400000 years Finally there is both the angle of rotation and the direction in which that axis points towards the Sun or away from it in cycles of about 41000 years and between 23000 and 26000 years respectively In another work Why Geography MattersMore Than Ever 2009 de Blij writes One of the most interesting developments in recent years has been the realization that the cycles just mentioned seem to dominate sequentially that is the timing of warn and cold spells may depend on what cycle or combination of cycles has the upper hand For example over the past million years it appears that 40000 to 50000year swings from warm to cold and back again dominated until about 420000 years ago when quite suddenly the cycles changed to 100000 year alternations
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