1. scientific evidence
   1. physical principles
      1. established over 100 yrs ago
      2. GHGs trap heat, warm planet
      3. inc GHG -> inc global temp
   2. record of distant past
      1. millions of years into past
      2. can't take stable climate for granted
      3. great variation in climate over earths history
         1. 10 major ice age cycles in last million years
      4. climate sensitive to small external influences
      5. last few thousand years quite stable
   3. measurements from recent past
      1. earth warming with increasing GHGs
      2. other environmental changes
      3. overall upward trend over last century clear
2. climate models
   1. warming will continue if GHGs not stabilised
   2. avg temp inc on pre industrial
      1. 2C
         1. more heatwaves
         2. fewer cold spells
         3. altered rainfall patterns
         4. higher global rainfall
         5. plant productivity changes
            1. higher in places
            2. lower in other areas
         6. disturbance to ecosystems
            1. marine
            2. terrestrial
         7. biodiversity disturbances
         8. disruption to food production
         9. sea level rise
         10. decreased arctic ice cover
         11. some may be beneficial in some regions but overall negative effect on current society
      2. 7C
         1. all of the above but much larger scale
         2. likely beyond adaptive capacity of
            1. societies
            2. species
   3. uncertainties
      1. pricise change values not possible
      2. climate sensitive to small changes
      3. plausible range of values based on past climate change data
      4. tipping points
         1. possible
         2. can't be predicted confidently
      5. change could be more or less severe than current estimates
3. What is CC?
   1. climate
      1. statistical descr of weather
         1. variations
         2. extremes
         3. averages
         4. can be defined for different regions or for entire earth
   2. weather changes
      1. day to day differences
      2. seasons
      3. year to year differences
         1. eg. el nino
      4. not climate change
   3. Climate change
      1. change in AVERAGE weather over long period of time
         1. decades or longer
      2. sustained change requires global heating or cooling influence
         1. diagram:
            1. positive feedback loop
         2. changes to suns heat output
         3. changes in earth's orbit around sun
         4. changes in surface ice coverage
         5. changes in cloudiness
         6. GHG concentrations in atmosphere
   4. GHG important in determining climate and changes
4. climate change in distant past
   1. enormous variety
   2. sensitive to small influences
   3. evidence of abrupt shifts
   4. positive feedbacks amplified changes to global temps
      1. likely that same feedbacks will occur when GHGs increased by humans
5. climate change in recent past
   1. avg temp increase
      1. evidence
         1. temp gauges in oceans and air
         2. trends
            1. sea levels
            2. glaciers
            3. ice caps
            4. water vapour content of air
            5. consistent with temp increase
         3. Subtopic 3
   2. Subtopic 2
6. caused by humans?
   1. human activity increasing GHGs
      1. very likely the reason for most of recent temp changes
7. future climate evolution
   1. warming will continue if GHGs continue to risse
   2. significant warming 21st century and beyond
   3. reduction of GHG emissions could reduce future warming signigicantly
8. impacts of CC
   1. on society
   2. on environment
   3. direct impacts
   4. altering impacts of other stresses
9. how to deal with the uncertainty of the science
   1. forecasts uncertain
      1. will remain this way
   2. broad conclusions of science
      1. high degree of confidence in them
      2. based on many lines of evidence
   3. considerations
      1. ethics
      2. economics
      3. risk management
      4. science