Evidence that the World has Warmed in the Late Nineteenth Century

?
View mindmap
  • 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
              • Untitled
    • 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

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all Climate Change resources »