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GS1004_lecture22note - Global Climate Change II Consequences of warming What we know Complexity of models What can be done I Possible implications

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Global Climate Change II Consequences of warming What we know Complexity of models What can be done I. Possible implications of global warming 1) sea-level rise : poles are more affected by warming; may rise up to 8 o C in winter, whereas tropics may only rise by 1 o C and global average only rises by 3 o C. -e.g. West Antarctic Ice Sheet = WAIS; 500,000 km 3 ice, if it melts, sea level rises by 20 ft. -ice sheets collapse into ice streams -moulins – meltwater melts ice; thermal erosion *A 1 meter rise in sea level would devastate New Orleans, Bangladesh, and many other major cities (e.g. Manhattan). *Sea level has risen nearly half a foot in the last 100 years. 2) locally intensified weather ; more storms, bigger storms. -there is a correlation between sea surface temperature, wind speed, and moisture content of hurricanes. 3) shifting climate patterns ; shifts in vegetation; spread of deserts, effect on agriculture (famine). Local changes in temperature and precipitation(natural or anthropogenic) can be devastating, regardless of the global mean temperature. Local change can be good (e.g. Wisconsin), but also bad (e.g. N. Africa). *Rapid climate change is bad; geopolitical boundaries are fixed. Societies and towns have become established over decades. Rapid warming can lead to warring and suffering. Global change in annual average precipitation = 20% increase over the last century, but major variation locally. Global climate is a very delicate system; it doesn’t take much to alter local patterns. II. What we know FACT 1) The earth is warming. Evidence: 1) glaciers are melting worldwide -Europe, S. America, Alaska, Canada, Tropics, Himalaya, Africa; glaciers everywhere are losing mass (with a few exceptions). 85% of glaciers worldwide are experiencing loss in volume. 2) Arctic sea ice extent (based on submarines and satellites) has declined 10% in the past 30 years. Positive feedback effect on warming. In a few decades, there may be no ice cap in summer -this has an additional warming effect on climate; lack of ice means more heat is absorbed by the darker color of the oceans (this is called albedo ; the degree to which heat is absorbed or reflected). 3) Melting permafrost. Warming has been more pronounced in high latitudes (polar). This also has a positive feedback effect with warming, because it releases stored methane, which is a greenhouse gas.
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-for example, winter travel days on frozen Alaska tundra have dropped from 200 in the 1970s, to about 100 now. 4)
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This note was uploaded on 09/26/2011 for the course GEOG 1004 at Virginia Tech.

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GS1004_lecture22note - Global Climate Change II Consequences of warming What we know Complexity of models What can be done I Possible implications

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