Feedback

• effect of positive feedback?

  this amplifies the effects of a change to a system
• Effects of negative feedback

  dampens the effect of a change to a system
• sometimes the same change to a system can cause EITHER a positive or negative feedback
• Example of positive feedback in the WATER cycle

  • temps rise
  • evaporation increases
  • amount of water vapour in atmosphere increases
  • greenhouse effect increases
  • (this is a cycle)
• Example of positive feedback in carbon cycle?

  • temps rise
  • plant respiration rate increases
  • amount of CO2 in atmosphere increases
  • greenhouse effect increases
  • (this is a cycle)
• negative feedback in the water cycle example

  • temps rise
  • evaporation increases
  • amount of water vapour in atmosphere increases, causing more clouds to form
  • increased cloud cover reflects more of Sun's energy back into space
  • Temps fall
• negative feedback in carbon cycle example

  • CO2 in atmosphere increases
  • extra CO2 causes plants to increase growth
  • Plants remove and store more CO2 from atmosphere
  • Amount of CO2 in atmosphere reduces
• in these examples, what would the positive feedbacks do?

  increase global warming because they are amplifying the temperature rise
• In these examples, what would the negative feedbacks do

  cancel out the temperature increase, so global warming would not increase