Systems and Feedback Loops

1. Systems and Feedback Loops

2. Questions for Today: • What is a system and it’s parts? • What are the different types of system response? (Positive and Negative Feedback Loops) • What is synergy and how is it harmful and beneficial?

3. The environment is difficult to study because… • A hypothesis must be testable • VARIABLES must be controlled and isolated • Too many interactions – known & unknown

4. More problems • Scale is often a problem • Populations over time • Environmental factors over centuries • Measurement is difficult • Species, pollutants, tons of soil

5. We do our best… • At best, we provide trends & estimates • Rely on models • Examples include climate models, ocean models, atmospheric models, etc.

6. Models • A representation or simulation of a system being studied • Can be mental, physical, graphical, mathematical, conceptual

7. Correlation • Relationship between two separate events • More CO2 and higher global temperatures

8. Correlation DOES NOT mean causation… • More lemons imported causes more traffic accidents?

9. Parts of a System • A system is a set of components that function and interact in some regular way. • Parts of a system • Inputs • Flows or thoroughputs • Outputs • Environmental scienctists use computer modeling to analyze systems.

10. System Vocabulary Stuff is processed Stuff comes out Stuff goes in • INPUT  matter, energy, information entering a system • THROUGHPUT  rate flow of matter, energy, or information through a system • OUTPUT  matter, energy, information leaving a system

11. Throughputs Outputs Energy Inputs Energy resources Heat Matter resources Waste and pollution Economy Goods and services Information Fig. 2-10, p. 44

12. Input  Throughput  Output

13. FEEDBACK LOOPS Stuff is processed Stuff comes out Stuff goes in Feedback Loop Change induces change

14. Feedback Loops • Systems respond to change through the use of feedback loops • Two types of feedback loops: • Positive – process that increases change • Negative - process that decreases change • Homeostasis

15. Negative Feedback Loops • The change counteracts the situation Examples: What happens when you’re hot? What happens when you’re cold?

16. Negative Feedback Loops • Negative, or corrective, feedback loops causes a system to change in the opposite direction from which it is moving. • Examples: • Thermostat • Recycling

17. House warms Temperature reaches desired setting and furnace goes off Furnace on House cools Temperature drops below desired setting and furnace goes on

18. Positive feedback Loops • The change compounds the situation = Snowball Effect! Example: As long as there are more human births than deaths, population will continue to increase.

19. Positive Feedback Loops • A feedback loop occurs when an output of matter, energy, or information, is fed back into the system as an input and leads to changes in that system. • A positive feedback loops causes a system to change further in the same direction. • Examples of Harmful Feedback loops: • Deforestation • Melting of Polar Ice Caps • Examples of Beneficial Feedback Loops: • Blood Clotting • Ecological Succession

20. Decreasing vegetation... ...which causes more vegetation to die. ...leads to erosion and nutrient loss... Fig. 2-11, p. 45

21. Pesticides:

22. Urban Sprawl

23. Synergy • Synergy is when two or more process interact so that the combined effects are greater than the sum of their separate effects. • Harmful Example: • Smoking and Asbestos leading to Lung Cancer • Air Pollutant Cocktails • Beneficial Example: • Writing your Congressmen (Cheesy, Huh?)

24. Positive or Negative • 1 person in a group of 10 has a cold. • That person passed the cold to another and soon 5 people now have the cold. • Those 5 students then each pass the cold to another.

25. Feedback Loops in Context Global warming says that the average temperature of Earth is increasing. During analysis, scientists have identified possible positive and negative feedback loops to explain atmospheric climate change. • http://science.howstuffworks.com/global-warming.htm

26. Radiation and Reflection

27. Positive or Negative? The warming of the oceans causes dissolved CO2 to bubble out into the atmosphere. This atmospheric CO2 helps to trap heat near the earth. This trapped heat continues to warm the ocean.

28. Positive or Negative? Warmer water temperatures cause greater water evaporation, which puts more water vapor in the air. More water vapor in the air traps heat inside the atmosphere.

29. Positive or Negative? The increased cloud cover from the last example might also act to reflect sunlight back into space, preventing it from entering our atmosphere. This might cool the earth.

30. Positive or Negative? Sunlight striking the earth is absorbed by dark colors and reflected by light colors. The polar ice caps act like huge mirrors, reflecting sunlight back into space. Warmer water temperatures are melting these ice caps and decreasing these big “mirrors,” leaving dark water behind.

31. Positive or Negative? Warmer temperatures cause greater water evaporation, which falls to earth as precipitation. Therefore global warming may cause increased snow fall in the polar regions, leading to increased snow and ice formation.

32. How did you do? • 1. Positive • 2. Positive • 3. Negative • 4. Positive • 5. Negative

33. Contemplate this… • What would Earth look like if there weren't any greenhouse effect at all? • It would probably look a lot like Mars. • Mars doesn't have a thick enough atmosphere to reflect enough heat back to the planet, so it gets very cold there.

34. Hmmmmm…. Some scientists have suggested that we could terraform the surface of Mars by sending "factories" that would spew water vapor and carbon dioxide into the air. If enough material could be generated, the atmosphere might start to thicken enough to retain more heat and allow plants to live on the surface.

35. Just like early Earth… • Once plants spread across Mars, they would start producing oxygen. • After a few hundred or thousand years, Mars might actually have an environment that humans could simply walk around in -- all thanks to the greenhouse effect.