Climate change - environmental systems and change.


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Climate change - environmental systems and change.

  1. 1. Climate Change<br />Hype or Reality?<br /><br />
  2. 2. Global System<br />
  3. 3. Conceptual Global Climate System<br />Consider alterations of processes within the system<br />Space<br />Earth<br />Atmosphere<br />Consider energy and mass transfers across system boundaries and processes or events that may alter their magnitude<br />
  4. 4. How do we know that climate is changing?<br />What is the best evidence??<br />
  5. 5. Individual Events CAN NOT be used<br /> As evidence of a trend!!!<br /> boscastle_flooding.jpg<br /><br /><br /><br />
  6. 6. Fossils<br />Ice Core<br /><br /><br /><br />Paintings<br /><br /><br />Tree Rings<br />Vineyards<br />
  7. 7. Mountain Treelines<br />
  8. 8.<br />Painting by Birman<br />1826<br />Mer de Glace: French Alps<br />2004<br />Athabasca Glacier: Canadian Rockies:<br /><br />
  9. 9. Famous Graph<br />Global records indicate 12 warmest years in the record have occurred since 1990 (record length 1881-2005)<br />2005, 1998, 2003, 2002, 2004, 2001, 1999, 1995, 1990, 1997, 1991, 2000<br />Newer version in IPCC 2007 report<br /><br />
  10. 10.
  11. 11. IPCC (Intergovernmental Panel on Climate Change) Verdict<br />“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea-level”<br />IPCC (2007) Summary for Policymakers, p5.<br />Notice past changes identified are gradual, not catastrophic storms/hazards etc<br />
  12. 12. Past Temporal Fluctuations<br />
  13. 13. Temporal Fluctuations<br />Source: Moran & Morgan (1994). Meteorology. Macmillan College Publishing Co., New York, NY<br />
  14. 14. Temporal Fluctuations<br />Source: Moran & Morgan (1994). Meteorology. Macmillan College Publishing Co., New York, NY<br />Whether we consider ourselves to be in comparatively warm or cool period is dependent upon length of time scale under investigation. Last 10,000 years indicates current relative cooler phase, whereas last 1,000 years shows relative warmer phase. Climate System is always changing!<br />
  15. 15. The Enhanced “Greenhouse Effect”<br />Heat increased due to elimination of advection, i.e. no heat is transported away from the surface<br />Heat increased by re-emission of energy by radiatively active gases<br />
  16. 16. Historic Carbon Dioxide Levels<br />Accepted idea that CO2 levels trigger climate change, positive relationship with temperature<br /><br />
  17. 17. Carbon Dioxide Levels vs Temperature?<br />Majority View: Sponge Effect?<br />Wavelength selective absorption<br />
  18. 18. Many influences on climate but they work at different time scales<br />Source: Moran & Morgan (1994). Meteorology. Macmillan College Publishing Co., New York, NY<br />
  19. 19. EXTERNAL FACTORS<br />Natural external forcing agents<br />Global solar energy<br />Sunspot cycles<br />Intergalactic dust<br />Impacts on global solar distribution<br />Milankovitch theory<br />
  20. 20. Solar Influence: SUNSPOTS<br />A) Cycle (approximately every 11 years)<br />B) Longer term fluctuation linked to European temperatures, e.g. Maunder minimum and the Little Ice Age (1645-1715)<br />Length of cycle linked to temperature?<br />Minor influence<br />Source:<br /><br />
  21. 21. Climatic Aspects and Sunspot Cycle<br />
  22. 22. Sunspot Cycle Length<br />
  23. 23. Long-time scale<br />
  24. 24. Milankovitch Hypothesis<br />Obliquity of rotation to orbital plane<br />Currently 23.4º but varies between 22º and 24.5º over a 41,000 year cycle<br />Greater influence felt towards the poles<br />Eccentricity of orbit around the sun<br />Varies from almost circular to more elliptical than present over two cycles, 96,000 and 413,000 years<br />Current annual variation of global solar energy approximately 5% but maximum variation of 30%<br />Precession of equinoxes<br />Defines the season when closest to the sun over a cycle of approximately 22,000 years<br />BUT TOTAL RADIATION REMAINS CONSTANT<br />
  25. 25. Milankovitch Cycles<br />Corresponds well with cycles from proxy data<br />Theory, in terms of variation of global radiation, insufficient to account for changes in global temperatures<br />Feedback effects must also contribute to climate change<br />Source:<br />
  26. 26. Milankovitch Cycles<br />Combined effect is to redistribute energy input<br />Total amount of radiation received by Earth in a year stays the same: so global effect?<br />Snow and ice amplify effects<br />In hemisphere with lower summer solar input and higher winter solar input – snow does not melt and ice sheets develop <br />– initiates an ICE AGE.<br />Dominance of N. Hemisphere<br />
  27. 27. NATURAL INTERNAL FACTORS<br />Natural Internal Forcing Agents<br />Solar Radiation forcing<br />Volcanoes<br />Earth evolution<br />Orogony (Mountain building)<br />Continental Drift<br />Increasing time scale <br />
  28. 28. VolcanicEruptions <br />Only lasts a couple of years<br /><br />
  29. 29. Dust Veil Index (DVI)<br />
  30. 30. Orogony and Continental Drift<br />Orogony<br />Mountain building due to tectonic forces<br />Increases upland area which may hold snow longer, thus increasing solar reflection - cooling<br />Continental Drift<br />Dictates ratio of land surface to ocean areas: supercontinents<br />Dictates where land and sea are located<br />Land and sea heat up differently and influence climate<br />VERY LONG TIMESCALE<br />Pangaea<br />
  31. 31. Continental Drift<br />High Latitudes and Altitudes : Snow and Ice<br />means high albedo and cooling<br /> Low Latitudes: Vegetation or Desert (depends on precipitation) – former means cooling through the CO2 effect, later means warming. <br />
  32. 32. HUMAN INTERNAL FACTORS<br />Anthropogenic Internal Forcing Agents<br />Human-based activity and land-use change such as urbanisation<br />Growth in existing natural background levels of greenhouse gases<br />
  33. 33. Humans: Land Use Change<br />Deforestation<br />Urbanisation<br />BUT: is this just local?<br /><br />
  34. 34. Major Greenhouse Gases<br />Source:<br />
  35. 35. Major Greenhouse Gases<br />Classified by activity type<br />
  36. 36. Humans: Greenhouse Gases<br />Current CO2 concentration: 380 ppmv – <br />Parts per million volume<br />Between 1970 and 2004, emissions have <br />increased by 70%<br />77% of total emissions is CO2<br />But also note methane (CH4)<br />and nitrous oxide (N2O)<br />Forecast concentration, by 2100:<br />500 – 1000 ppmv (wide range indicates economic uncertainty<br />
  37. 37. GWP (Global Warming Potential)<br />Note that methane is 63 times more powerful in the short term but has a relatively shorter atmospheric lifespan, hence only 9 times more powerful over 500 years <br />
  38. 38. Composite Model<br />Combination of known factors appear to explain major changes in global climate<br />Some doubt cast upon validity – see Idso, K.E. (2001) Predicting the past: Its not that difficult at<br />Source: Gilliland, R.L.  1982.  Solar, volcanic, and CO2 forcing of recent climate changes.  Climatic Change4: 111-131. <br />
  39. 39. The Future?<br />Predictions based on modelling<br />Energy Balance Models<br />Global Climate Models<br />Scenarios of CO2 consumption used: modelling of economics as well as atmosphere<br />AIFI scenario leads to doubling of CO2 by 2050, and 1550 ppm by 2100.<br />Alternative lesser increases used to indicate global action: B1 (600 ppm by 2100), AIT, B2, AIB, A2 <br />
  40. 40. Carbon Dioxide vs Temperature?<br />NON-LINEAR<br />Fatalistic Viewpoint<br />Thresholds<br />
  41. 41. Global Carbon Cycle<br />SMALL<br />Problem:<br />Figures don’t balance<br />BIG<br /> <br />
  42. 42. More cloud<br />Less cloud?<br />-ve<br />Less surface heating<br />Less convection<br />Surface heating<br />Reduced albedo<br />+ve<br />Melting<br />Less ice<br />Possible Feedback Loops<br />Clouds<br />Ice/Snow<br />
  43. 43. UNKNOWNS<br />Permafrost: Methane Release<br /><br /><br />
  44. 44. Problems with GCM’s<br />Clouds not incorporated well<br />Serious deficiencies in treatment<br />Changes in snow/ice cover badly modelled<br />Albedo of snow highly significan<br />Coupling of ocean and atmosphere<br />Thermal inertia of ocean systems<br />Polewards transport of energy<br />More confidence with temperature predictions than rainfall predictions: smooth vs spotty distribution<br />Feedbacks can lead to instability in the model<br />
  45. 45. Future Predictions<br />Intergovernmental Panel on Climate Change(IPCC)<br />Predictions updated 1990, 1996 and 2001, 2007<br />Global<br />Current rates of warming around 0.1-0.2 deg C/decade<br />Current mean estimate of 1.8ºC<>4.0ºC by 2100 (depends on scenario)<br />Constant 2000 concentrations: 0.6°C by 2100 (lag)<br />Regional (see map)<br />
  46. 46. Two main climate model types<br />One way to avoid economic uncertainty is to predict for 2 *CO2, NOT a date<br />Transient (time series) – takes time to adjust<br />Equilibrium: 1 * C02 vs 2 * CO2<br />Model allowed to come into equilibrium<br />Take the difference between the two predictions, i.e. + 2 deg C<br />
  47. 47. Future Global change<br />2 times CO2<br />Most warming: Land, N hemisphere: Least certain: mid-latitudes<br />Green lines represent areas of uncertainty<br />
  48. 48. Regional Detail: Europe: Hadley Centre GCM<br />Annual Precip<br />Note relatively<br />poor grid resolution<br />Annual Temp<br />Winter Precip<br />Summer Precip<br />
  49. 49. PREDICTING EFFECTS is not just <br />temperature and precipitation?<br />Most of the warming is focused in currently cold areas<br />(snow and ice feedback) <br />Logically this should reduce temporal <br />and spatial variability of Earth’s climate at the surface<br />This may influence extreme events? <br />
  50. 50. Thunder<br />Extreme Events: Storminess<br />Waves<br />Wind<br />Ice and Snow<br />Rain<br />
  51. 51. Storm Tracks and GW<br />
  52. 52. North Atlantic Cyclones: Western Europe<br />F<br />I<br />Timeseries of the number of storm events recorded at 24 hour intervals. <br />Timeseries of average intensity (mean pressure gradients)<br />Sym<br />FSevere<br />Timeseries of the number of severe lows (max gradient greater than or equal to 45m/250km)<br />Timeseries of mean symmetry index<br />Source: Amanda Gibson (2006): Unpublished phD Thesis<br />
  53. 53. Hurricanes: Uncertain <br />Increase over N Atlantic<br />From 1995 to present, but<br />There were similar high <br />frequencies in the 1950s. <br />Maybe a cycle: Maybe not?<br />Statistics are inconclusive<br />
  54. 54. Tornadoes:<br />Uncertain Data<br />Changes in reporting<br />and better detection<br />makes the data <br />inhomogenous<br />
  55. 55. Mountains<br />Complicated landscape<br />
  56. 56. Glacial Change in East Africa<br />
  57. 57. Polar Regions<br />Sensitive to change, snow is a natural cooling system, protects the ground<br />as an insulator, frozen lakes can be used for transport, hunting etc.<br />
  58. 58. Mediterranean: Desertification<br />
  59. 59. Portsmouth: coastal flooding: Old Portsmouth 1989, but also both more and less rainfall?<br />
  60. 60. So what can we do?<br />Figure 1. Global average temperature change projected from 16 different climate models for the 21st century if atmospheric CO2 levels are held constant at the year 2000 levels.<br />Figure 1. Global average temperature change projected from 16 different climate models for the 21st century if atmospheric CO2 levels are held constant at the year 2000 levels.<br /><br />Sceptic website!<br />
  61. 61. Future scenarios<br />Source: IPCC 2007 Report: Mitigation of Climate Change<br />
  62. 62. Conceptual Global Climate System<br />Short-wave and long-wave energy balance<br />Sunspot Cycles<br />Orbital Cycles<br />Interstellar Dust <br />Radiative Forcing<br />Atmospheric Chemistry<br />Volcanic Dust<br />Gas Emissions<br />Solar Energy<br />Terrestrial Energy<br />Solar Energy<br />Surface Conditions<br />Thermodynamic Forcing<br />Global Circulation Systems<br />
  63. 63. SUMMARY POINTS<br />Climate change at many time scales: past changes have been caused by many mechanisms superimposed upon one another<br />Changes in mean temperature and or precipitation may be seen in the past reconstructions and modelled in the GCMs, but this is not the whole description of climate<br />Extreme events are a real problem! to predict and understand! They are also not good to use as evidence of past or current climate change, and there is much uncertainty here.<br />Many unknowns concerning degree and extent of response – we are interfering with a complex system <br />Surely we should limit our interference as much as possible even though there are scientific and economic uncertainties?<br />
  64. 64. Internet Resources<br /> A useful site belonging to Climate Action Network Europe, great links<br /> The Intergovernmental Panel on Climate Change: <br />Read the 2007 Scientific Basis report<br /> Met Office<br />Web site gives some model data and predictions for the future<br /> Climate science from climate scientists<br /> Alternative viewpoint<br /> Local action network for climate change mitigation<br />
  65. 65. CHAOS<br />CHAOS<br />CHAOS<br />CHAOS<br />CHAOS<br />CHAOS<br />CHAOS<br />CHAOS<br />CHAOS<br />