Climate Change

Climate Change

1. Evidence

   • Long-term
     • Past 400,000 years - more detailed fluctuation
       • Cold glacial periods - 100,000 years
       • Warmer inter-glacial periods - 10,000 years
       • Currently interglacial
     • Ice cores
       • Layer of ice formed every year
       • Drill deep into ice to retrieve a core
       • Analyse trapped gasses to determine temp. each year
     • Pollen analysis
       • Pollen often preserved in sediment
       • Pollen can be identified and dated
       • Pollen from similar plants indicates similar conditions
     • Sea level change
       • Affected by volume of water stored as ice
       • Sea level shown by raised beaches
         • Can be dated, indicating less ice so warmer periods
   • Medium-term
     • Last glacial period 18,000 years ago
     • 5,000 years ago, temperatures were 1-2Oc higher than today
     • Historical records
       • Agricultural reports
       • Indirect indicator
     • Tree rings
       • Ring formed each year
       • Good conditions lead to thick ring
       • Take cores and count rings to find age
         • Analyse each ring to determine climate every year
       • Reliably show and date conditions up to 10,000 years
     • Retreating glaciers
       • Size and extension determined by deposited rocks
         • Rocks can be dated to show when deposited
       • Distance from rocks determines climate change
         • Rocks miles away - increased temperatures
   • Short-term
     • Sharp rise over past 1,000 years
     • General increase shown - pattern not constant
     • Weather records
       • Collected since 1861
       • Show climate change per short period of time
     • Polar ice melt
       • Reduction of ice at both poles
       • Increased melting = increased temperatures
     • Ecosystem changes
       • Temperature affects food and shelter
       • Affects species in different areas
       • Analyse species to indicate climate changes

2. Causes

   • Natural
     • Milankovitch Cycle
       • Orbit
         • Circle - ellipse every 96,000 years
       • Tilt
         • Varies between 21.8 - 14.4 over 41,000 years
       • Wobble
         • Wobbles like a spinning top every 22,000 years
     • Solar Output
       • Sunspots show increased solar output
       • Thought to increase and decrease over 11 year cycle
     • Eruptions
       • Place large quantities of ash into atmosphere
       • Block out solar radiation
       • Cool Earth
   • Human
     • Enhanced greenhouse gas emissions
       • Too much greenhouse gas in atmosphere, warming Earth
       • Fossil fuels
         • Coal power stations
         • Transport
     • Destruction of Co2 sinks
       • Oceans and plants
       • Deforestation
       • Increased emissions mean sinks can't keep up

3. Impacts

   • Melting Ice
     • Water stored as ice returns to oceans
       • Rising sea level
         • Eustatic sea level rise
   • Oceans get warmer
     • Expand - thermal expansion
   • Thawing permafrost
     • Ground frozen for 2+ years
     • Permafrost are natural sinks
     • Releases Co2
     • Collapse of buildings and pipelines built on it
   • Increase in frequency of extreme weather events
   • Changes in distributions of climatic regions
   • Difficult to predict climate change as too much uncertainty
   • Possible Tipping Point
     • Catastrophic and irreversible changes
       • e.g. ice melt + destruction of natural Co2 sinks