Evidence that the World has Warmed in the Late Nineteenth Century
- Created by: Eleanor_kittle
- Created on: 10-02-19 12:25
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- Evidence that the Earth has Warmed since the Late Nineteenth Century
- Increase in Global Temperatures
- Consistent rise of global land and ocean temperatures in the C20
- Shrinking Valley Glaciers and Ice Sheets
- Everywhere in the past century, valley glaciers have been retreating and some have completely disappeared
- If trend continues, valley glaciers in the Alps may shrink by 80-96% by the end of the century
- Present day melting of polar ice sheets adds approximately 1mm to sea level every year
- Losses are due to:
- Warming of the atmosphere, which melts the ice surface
- Warming, which produces meltwater that penetrates the ice and increased the velocity of glacial flow
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- Losses are due to:
- Present day melting of polar ice sheets adds approximately 1mm to sea level every year
- If trend continues, valley glaciers in the Alps may shrink by 80-96% by the end of the century
- Everywhere in the past century, valley glaciers have been retreating and some have completely disappeared
- Rising Sea Level
- Began to rise mid-nineteenthcentury
- Since 1900 the average rise has been 1.0-2.5 mm/year
- Recent satellite imagery suggests a faster rate - 3mm/year
- Two processes account for the global sea level rise:
- The thermal expansion of oceans as the worlds climate warms
- The melting of land-based ice sheets and glaciers
- Increasing Atmospheric Water Vapour
- The most important greenhouse gas (GHG)
- It traps huge amounts of energy radiated from the Earth's surface and creates a natural greenhouse affect
- Amount of water vapour in the atmosphere is directly related to temperature and rates of evaporation
- In a warmer world there will be more atmospheric moisture
- For every 1 degree increase in temperature caused by enhancingCO2 levels, rising levels of water vapour will double the warming
- Large concentrations of water vapour will amplify the effects of warming on positive feedback; hence more vapour intensifies the greenhouse effect
- Increases evaporation, which in turn leads to more atmospheric vapour, more evaporation, more warming...
- Decreasing snow cover and sea ice
- 2% decline per decade since 1966 in the northern hemisphere
- Snow has a high albedo, reflecting 70-80% of incoming solar radiation compared with just 10-20% for soil and vegitation surfaces
- Demising snow cover therefore increases the absorption of solar radiation
- With the suns energy being used to warm the ground air temperatures rise
- Creates positive feedback, which explains the rapid warming currently taking place in the Arctic
- Arctic sea ice has declined dramatically - 8% in summer and 3-4% in winter
- Also decreasedthickness
- Less sea ice results in more solar energy absorption by open sea surface, raising air temperatures and causing even more rapid melting
- Increase in Global Temperatures
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