The Climate System

1. The Climate System Global climate is: Driven by solar radiation (Earth�s external heat engine) Composed of diverse, interrelated components that function as a whole

2. Components of the Climate System

3. Climate System

4. Systems Approach Systems Comprised of diverse components that function as a whole Climate System Flow of energy and mass between components Change in one component will affect other components Linked (coupled) interactions

5. Climate System Example of coupling Increase seafloor spreading rate (volcanism) More CO2 to atmosphere Warmer climate Melt ice Raise sea level Alters ocean circulation Alters distribution of nutrients- productivity Impact on CO2�.

7. Climate System Interactions: Complex Each component works at a different rate Feedbacks Complicated Nonlinear patterns of variation

8. Components of the Climate System Discuss each component in terms of: Response time- how quickly it responds to inputs Heat capacity- amount of energy that must be put into the component to cause a change Albedo -reflectivity of incoming short wave radiation

9. Atmosphere Response time Strong diurnal cycle Fastest response to perturbation- days to months Mixes globally in months to years Heat Capacity Low heat capacity (~1 J/gK) Easily heated and set into motion Strong vertical and horizontal gradients

10. Atmosphere Albedo Clouds reflect 50-55% Clear skies reflect ~5% Coupled to other systems through energy and chemical exchanges Evaporation/precipitation Wind stress Trace gas exchange

11. Hydrosphere Mostly the ocean (97.3% of the world�s water) Response time- Layered Surface ocean- mixed layer (~100 m) Months to years (seasonal cycle) Deep ocean (~100 m to seafloor) Centuries to 1000�s years (mixes in ~1500 yrs)

12. Hydrosphere Heat Capacity Very high (4 J/gK) Stores heat and buffers the system against change Albedo Ocean surface ~8%

13. Hydrosphere Coupled to other components through exchange of energy and mass Evaporation/precipitation Trace gas exchange Land/sea boundary defined by sea level Drives chemical reactions (weathering) Necessary for life (photosynthesis)

14. Cryosphere- Ice Cryosphere includes: continental ice sheets, mountain glaciers, ice shelves, sea ice, snow, permafrost Currently 6% of Earth permanently covered by ice (highly variable) 3 major ice ages during past 570 My

15. Cryosphere- Ice

16. Last Ice AgeLast Glacial Maximum

17. Cryosphere Antarctic Ice Sheet (AAIS) 60% of world�s fresh water Sea level would rise 73 m if AAIS melted (7.4 m sea level rise if Greenland melted)

18. Cryosphere

19. Cryosphere

20. Cryosphere Response time- multiple time scales Rapid seasonal variations- annual meltback Observed decadal changes Ice sheet growth- 10,000 to 100,000 yrs Ice sheet decay- 1,000 to 10,000 yrs Heat Capacity Moderate (2 J/gK)- lots of energy required for phase transition (melting)

21. Cryosphere Albedo Primary role in climate system = reflectivity Highly reflective Old snow ~50% Fresh snow 80-90%

22. Geosphere Sluggish component of climate system Response time- time scales of interactions tend to be slow Plate tectonic motion ~1cm/yr Weathering- global average ~6cm/1000y Millions of years to produce a significant effect Volcanic eruptions- instantaneous effect on atmospheric timescales

23. Geosphere

24. Plate Tectonic Boundaries

25. Geosphere Heat capacity Low (0.25x water = 0.8 J/gK) �Continentality� Because of differences in heat capacities Latitudinal distribution of land and sea and Sea level Are important climate factors

27. Geosphere Albedo Dark soil ~10% Light soil ~30% Black top~5-10% Concrete ~20% Major impacts on climate Continentality Paleogeography (Plate tectonics) Weathering and seafloor spreading (CO2) Topography (atm circulation)

28. Biosphere Can include people (anthropogenic effects) Response time Individuals � seasonal or annual Communities- centuries

29. Biosphere

30. Biosphere Albedo Forests ~5-10% Meadows and crops ~5-25% Rainforests- lowest albedo on Earth Important contributions to climate Photosynthesis-Atmospheric composition Evapotranspiration Albedo (forest ~10%; soil ~25%)

31. Properties of a System Components System made up of diverse components that function as a whole- linked Flow of energy and mass between components (electric blanket example)

32. Properties of a System Equilibrium State State of the system that will not change unless there is a disturbance Stable Equilibrium State system will return to if disturbed slightly Unstable Equilibrium A small disturbance will carry the system away from one equilibrium state until it reaches a new equilibrium state Threshold event Small change that causes the system to shift from one equilibrium state to another

33. Properties of a System

34. Properties of a System Disturbances Perturbation Temporary disturbance Mt Pinatubo eruption- climate cooled for several years then returned to previous state Forcing A more persistent disturbance Global warming

35. Properties of a System Feedback loops A particular type of interaction between components of a system A change in Component 1 elicits a change in Component 2, which in turn comes back to affect Component 1 Requires a disturbance/perturbation/forcing to initiate the change

36. Feedback Loops Positive Feedback Loop Interactions amplify the effects of the disturbance Negative feedback loop Interactions diminish the effects of the disturbance

37. Positive Feedback Loop (amplifies) Temperature decreases Ice grows

39. Negative Feedback Loop (diminishes)

41. Climate Change �Change� Compare climate state at one time to some time in the past or the future Requires record of past climate or predictions of future climate Past- Proxies and archives- records of previous conditions Future- models

42. Proxies and ArchivesExamples

43. Climate Variability Periodic (seasons, glacials) Quasiperiodic (El Ni�o) Chaotic Transition to new equilibrium state Threshold event Gradual

44. Climate Variability

45. Climate VariabilityPeriodic- Ice Ages

46. Climate VariabilityEl Nino- quasiperiodic

47. Climate Variability

48. Climate SystemSummary Climate can change in a number of ways in response to forcing Sometimes at a stable equilibrium Lots of forcing required to instigate a change Sometimes near a transition to a new equilibrium Small forcing can lead to dramatic change (threshold events) Response can be linear or nonlinear