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Physical Science Basis of Climate Change : IPCC 2007

Physical Science Basis of Climate Change : IPCC 2007

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Physical Science Basis of Climate Change : IPCC 2007

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  1. Physical Science Basis of Climate Change: IPCC 2007 Chapter 7: Couplings Between Changes in theClimate System and Biogeochemistry Emilia K. Jin

  2. Contents • Feedbacks • Global Carbon -Climate System • Land - Climate Interaction • Ocean - Climate Interaction • Reactive Gases • Aerosol Bottom Line: Carbon – Climate feedbacks are critically important for predicting future climate change, but the more we learn the more we realize that we do not understand…

  3. Contents • Feedbacks • Global Carbon -Climate System • Land - Climate Interaction • Ocean - Climate Interaction • Reactive Gases • Aerosol

  4. Couplings Between Changes in theClimate System and Biogeochemistry • To identify the major biogeochemical feedbacks of significance to the climate system, and to assess current knowledge of their magnitudes and trends. • Examine the relationships betweenthe physical climate system and the land surface, the carbon cycle,chemically reactive atmospheric gases and aerosol particles. •  There are large uncertaintiesto provide a simple quantitative description. Biogeochemical cycling • Natural and anthropogenic emissions of gases and aerosols • Transport at a variety of scales, chemical and microphysical transformations • Wet scavenging and surface uptake by the land and terrestrial ecosystems • Wet scavenging and surface uptakeby the ocean and its ecosystems. Earth’s Climate Nonlinearinteractions between/within thedifferent components of the Earth system Radiativeproperties of the atmosphere Complexconnected physical, chemical and biological processesoccurring in the atmosphere, land and ocean. Composition of the atmosphere Biophysical state of the Earth’s surface : LLGHGs, CO2, CH4, N2O, ozone, and aerosol particles.

  5. Radiative Forcing Components and Their Feedbacks to the Climate System • Largest forecers are CO2, CH4, aerosols, ozone, and surface albedo (reflectivity). • They all involve potential feedbacks to the climate system, usually through biogeochemistry. • Nonlinear interactions between the climate and biogeochemical systems could amplify or attenuate the disturbances produced by human activities.

  6. Positive vs. Negative Feedback • Something triggers a small system change • The system responds to the change • Feedback • Positive Feedback: The response accelerates the original change • Negative Feedback: The response damps the original change

  7. Effect of Positive Feedback (1) With positive feedbacks Temperature If no feedbacks present Time

  8. Effect of Positive Feedback (2) If no feedbacks present Temperature With positive feedbacks Time

  9. The Need for Negative Feedbacks • Positive feedbacks are destabilizing - they tend to drive the system away from equilibrium • Negative feedbacks are required to restore equilibrium

  10. A System Without Negative Feedbacks Example “Runaway Greenhouse Effect”, T  H2O  T Catastrophic Warming! Temperature Time

  11. The Way Physical Systems Usually Behave Temperature Warming Accelerating Warming Decelerating Time

  12. Feedbacks - Summary • Positive feedbacks tend to increase the amplitude of the system response • Negative feedbacks tend to reduce the amplitude of the system response

  13. Feedbacks in the Biosphere • 1. The plankton multiplier in the ocean (positive) • (Colder  Stronger Ocean Biological Pump  Remove ATM CO2) • 2. Carbon dioxide fertilization, plant growth (negative) • 3. Effect of higher temperatures on respiration (positive) • 4. Reduction of forest growth because of climate change (positive) • 5. Increased greenhouse gases due to increase of fires (positive) • 6. Release of methane from wetland and permafrost (positive)

  14. Feedbacks in the Climate System • Water vapor feedback • Cloud-radiation feedback • Ice-albedo feedback • Climate-Carbon Cycle feedback

  15. Ice-Albedo Feedback (1) Cooling Ice Increases Albedo Increases Absorption of sunlight decreases

  16. Ice-Albedo Feedback (2) Warming Ice Decreases Albedo Decreases Absorption of sunlight increases

  17. Water Vapor Feedback (1) Warming Evaporation from the Oceans Increases Atmospheric Water Vapor Increases Stronger Greenhouse Effect

  18. Water Vapor Feedback (2) Cooling Evaporation from the Oceans Decreases Atmospheric Water Vapor Decreases Weaker Greenhouse Effect Water Vapor Feedback is Positive

  19. Understanding and Attributing Climate Change • 1. Equilibrium Climate Sensitivity (ECS) and Transient Climate Response (TCR) • Definitions • Model ECS and TCR—the role of feedbacks • 2. Detection and Attribution • Detection and Attribution of What? • Modeling with and without anthropogenic forcing • 3. Understanding?

  20. Equilibrium Climate Sensitivity (ECS) and Transient Climate Response (TCR) • Definition: The ECS is the full equilibrium surface temperature response to a doubling of CO2 • Definition: The TCR is the surface temperature response at CO2 doubling for a 1%/yr increase of CO2 (i.e. at year 70) • a. ECS and TCR are basically model concepts • b. TCR < ECS • c. ECS is a measure of the feedbacks in the system: • Recall:

  21. Climate Model Fidelity and Projections of Climate Change J. Shukla, T. DelSole, M. Fennessy, J. Kinter and D. Paolino Geophys. Research Letters, 33, doi10.1029/2005GL025579, 2006

  22. Contents • Feedbacks • Global Carbon -Climate System • Land - Climate Interaction • Ocean - Climate Interaction • Reactive Gases • Aerosol

  23. Carbon Dioxide Raupachet al., 2007 PNAS

  24. Carbon Dioxide Raupachet al., 2007 PNAS

  25. Carbon Dioxide Raupachet al., 2007 PNAS

  26. Carbon Dioxide Raupachet al., in press. PNAS

  27. Fraction of the CO2 emitted by human activities which remains in the atmosphere airborne fraction =atm / (fossil fuel + cement + land use emissions)

  28. Fraction of the CO2 emitted by human activities which remains in the atmosphere airborne fraction =atm / (fossil fuel + cement + land use emissions)

  29. Carbon Dioxide • • The rate of increase of CO2 emissions from fossil fuels has been increasing (top line) • • The rate of increase of atmospheric CO2 has been increasing • Bars : yearly • Solid lines : 5-year means (Black for SCRIPPS Red for NOAA) • • Less so since 1990 * 2.1 Gt-C of CO2 is equivalent to 1 ppm concentration in the atmosphere

  30. Carbon Dioxide CO2 Concentration Remained in the ATM.

  31. Are there changes in the efficiency of the land and/or ocean sinks for CO2 ?

  32. Climate Change Scenarios

  33. Climate Change Scenarios, Predicting Climate Change of the Future and the IPCC Assessments The problem of projecting the future climate has many aspects. One way to make a prediction is to predict the concentration of GHG in the future and apply that future concentration to a climate system model to determine how the climate system will respond. There are three critical issues: The projection of future GHG concentrations depends on the future emissions The future concentration of GHG depend on the uptake of emitted GHG by various parts of the climate system The simulated response of the future climate system depends on how well the climate system model simulates the current climate For issue #1, the IPCC makes use of the SRES (Special Report on Emission Scenarios) http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/emission/

  34. The IPCC Assessments of ClimateChange and Uncertainties • The six IPCC scenarios arespline fits to projections (initialized with observations for 1990) of possiblefuture emissions for four scenario families, A1, A2, B1, and B2, which emphasizeglobalized vs. regionalized development on the A,B axis and economicgrowth vs. environmental stewardship on the 1,2 axis. • Three variants of the A1(globalized, economically oriented) scenario lead to different emissions trajectories:A1FI (intensive dependence on fossil fuels), A1T (alternative technologieslargely replace fossil fuels), and A1B (balanced energy supply betweenfossil fuels and alternatives).

  35. The IPCC AR4

  36. The IPCC Assessments of ClimateChange and Uncertainties Different scenarios: A1. The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B) (where “balanced” is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies). A2. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines. B1. The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives. B2. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

  37. IPCC SRES Emission Scenarios(The Emission Scenarios of the IPCC special Report on Emission Scenarios) Pg (Petagram) =1015 g = Gt (Gigaton)