CLIMATE CHANGE - CLIMATE CHANGE It is obvious that climates...

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CLIMATE CHANGE It is obvious that climates have changed throughout geological history because of different types of rocks & sediments, different kinds of fossils (animals, plants, pollen, shells etc). In the last 100-200 years there has also been instrumental evidence of climate change for certain localities (mainly limited to land areas). It has only been in the last 20-30 years with the advent of satellites for continuous global data acquisition & computers for data storage, analysis & modelling that it has been possible to view atmospheric processes over the oceans, to see changes & also factor the changes into climate models for the future (e.g. The Atmospheric General Circulation Model or AGCM) The satellites, however, record data from aloft & not from the sea surface & we do not know much about what goes on there because weather ships are not in general use anymore. It appears that climate variability has increased significantly since the K/T (Cretaceous/Tertiary) Boundary (~60-65 MA). This variability has been seen: In the general cooling of the temperatures since the Cretaceous, The Glacial/Interglacial cycles of the Pleistocene Epoch (since ~ 2.5MA). Complex glacial periods of ~100,000 years separated by complex Interglacials of ~10-20,000 years. ‘Complex’ meaning that they had a succession of different climates & environments, e.g. The Interglacial Pollen Zones indicate the following sequence: There is archaeological & historical evidence of climatic change in the Holocene Interglacial. The climatic optimum (highest temperatures & greatest humidity) for the interglacial occurred from 8,000 to 5,000YBP (The Hypsithermal Period) The early Middles Ages Warm Phase saw the Viking Exploration & Settlements in The Little Ice Age (LIA) started in the Later Middle Ages & lasted for ~300 years (~1550-1850CE). The Thames froze to ~30cm for 2 months during the Great Frost of 1684. The sea was The years that the Thames froze for an extended period of time: 1408, 1435, 1506, 1514, 1537, 1565, 1595, 1608, 1621, 1635, 1649, 1655, 1663, 1666, 1677, 1684, 1688/89, 1695, 1708/9, 1715/16, 1739/40, 1768, 1775, 1784/85/86 (eruption of Laki), 1788/89, 1794/5 & 1814, 1816 (eruption of Tambora) 1829/30 & 1837/8. Hasn’t frozen solid since.
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The LIA was associated with colder temperatures, more snow & neoglaciation with glaciers growing in size. Since ~1850 there has been a warming of temperatures & a retreat of the glaciers.
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This note was uploaded on 04/06/2012 for the course GEOG 1600 taught by Professor Roger during the Fall '12 term at York University.

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CLIMATE CHANGE - CLIMATE CHANGE It is obvious that climates...

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