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Projected Future Changes

Projected Future Changes. Primary Source: IPCC WG-I Chapter 10 - Global Climate Projections. Part 1: Projected Radiative Forcing. Language Problem: Forecast. IPCC does not talk about “forecasting” or “predicting” future climate. Why?.

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Projected Future Changes

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  1. Projected Future Changes Primary Source: IPCC WG-I Chapter 10 - Global Climate Projections

  2. Part 1: Projected Radiative Forcing

  3. Language Problem: Forecast IPCC does not talk about “forecasting” or “predicting” future climate. Why? • A “forecast” implies that we know (or think we know) all the factors that determine the future - even though we may know them only imperfectly.Some important factors we do not know for the future: What will humans do about GHG emissions, aerosol generation and land use? When and where will volcanoes erupt, and how strongly?

  4. Terminology: Projection To recognize this uncertainty, many climate scientists describe a simulation of possible future climate as a projection. IPCC: “A projection is a potential future evolution of a quantity or set of quantities, often computed with the aid of a model.”

  5. Special Report on Emission Scenarios (SRES) IPCC Working Group III produced a set of possible future emissions scenarios, described in special IPCC report (see supplemental material). • The IPCC AR4 focuses on three: B1 - a “low” emissions future, global cooperation A1B - a “medium” emissions future A2 - a “high” emissions future, regional fragmentation There is no probability weighting to these scenarios: each is considered equally credible.

  6. SRES Scenarios vs. Time

  7. Steps from Scenario to Climate Change Radiation schemes and parameterizations Climate system models Biogeochemical models

  8. Radiative ForcingsGCM vs Line-by-line What is “line-by-line”?

  9. Radiative ForcingsGCM vs Line-by-line Doubled CO2 20% increase in water vapor

  10. Radiative ForcingsSRES A1B 2000-2100 Longwave (infrared) Shortwave (solar) aerosol uncertainty

  11. EndPart 1: Projected Radiative Forcing

  12. Part 2: Projected Climate Change - Atmosphere & Water Cycle

  13. Projections of Future Changes in Climate

  14. Stabilization of Future Changes in Climate

  15. Latitudinal Pattern of Temperature Change (2080 - 2099) minus (1980 - 1999) Ratio: Local change / Global average T Actual change

  16. Latitude-Height Temperature Changes A1B (“medium”) scenario relative to 1980-1999 Stippling: multi-model ensemble mean > standard deviation between models

  17. Surface Temperature Changes Relative to 1980-1999

  18. Latitudinal Pattern of Precipitation Change (2080 - 2099) minus (1980 - 1999) Ratio: Local change / Global average T Actual change

  19. Surface Temperature, Precipitation and Pressure Changes Relative to 1980-1999 Stippling: multi-model ensemble mean > standard deviation between models

  20. Changes in Cloud Cover [fraction] A1B (“medium”) scenario relative to 1980-1999

  21. Changes in Diurnal Temperature Range A1B (“medium”) scenario relative to 1980-1999

  22. Changes in Precipitation Characteristics

  23. Changes in Water Cycle

  24. EndPart 2: Projected Climate Change - Atmosphere & Water Cycle

  25. Part 3: Projected Climate Change - Oceans & Extremes

  26. Latitude-Height Temperature Changes A1B (“medium”) scenario relative to 1980-1999 Stippling: multi-model ensemble mean > standard deviation between models

  27. Changes in Area of Sea Ice

  28. Changes in Distribution of Sea Ice

  29. Changes in tropical Pacific SSTs and El Niño Variability

  30. Changes in Extremes: Very Warm Nights For North America (Wehner, 2008)

  31. Changes in Extremes: Heavy Precipitation For North America (Wehner, 2008)

  32. Changes in Extremes Standard deviation scale used to combine results from multiple models

  33. Factors Affecting Hurricane Development A1B scenario 18 GCMs (Vecchi and Soden, 2007)

  34. Changes Hurricane Intensity Idealized Simulations with High Resolution Model Future: 80-year warming from 1%/year CO2 increase (Knutson and Tuleya, 2004)

  35. Sea Level Rise due to Thermal Expansion Observed: 1961-2003: 0.4 ± 0.1 mm/yr 1993-2003: 1.6 ± 0.5 mm/yr Models (A1B): 2000-2020: 1.3 ± 0.7 mm/yr

  36. Local Sea Level Change due to Density and Circulation Changes Freshening of water? Wind changes? Low thermal expansivity? Stippling: ensemble mean > stdev between models “+” = greater than global average

  37. Sea-Level Rise: 2090-2099 from 1980-1999

  38. EndPart 3: Projected Climate Change - Oceans & Extremes

  39. END Global Climate Projections

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