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An Introduction to Climate Models: Principles and Applications

An Introduction to Climate Models: Principles and Applications. William D. Collins National Center for Atmospheric Research Boulder, Colorado USA. Topics. The climate-change context Components of the climate system Representation of climate in global models The NCAR climate model CCSM3

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An Introduction to Climate Models: Principles and Applications

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  1. An Introduction to Climate Models:Principles and Applications William D. Collins National Center for Atmospheric Research Boulder, Colorado USA Colloquium on Climate and Health 17 July 2006

  2. Topics • The climate-change context • Components of the climate system • Representation of climate in global models • The NCAR climate model CCSM3 • Applications to global change • Transition from climate models to Earth system models Colloquium on Climate and Health 17 July 2006

  3. Climate Simulations for the IPCC AR4(IPCC = Intergovernmental Panel on Climate Change) IPCC Emissions Scenarios Climate Change Simulations IPCC 4th Assessment • Results: • 10,000 simulated years • Largest submission to IPCC • 100 TB of model output 2007 Colloquium on Climate and Health 17 July 2006

  4. Exchange of Energy in the Climate Colloquium on Climate and Health 17 July 2006

  5. Components of the Climate System Colloquium on Climate and Health 17 July 2006 Slingo

  6. Time Scales in the Climate System Colloquium on Climate and Health 17 July 2006

  7. Configuration of NCAR CCSM3(Community Climate System Model) Atmosphere (CAM 3.0) T85 (1.4o) Land (CLM2.2) T85 (1.4o) Sea Ice (CSIM 4) (1o) Coupler (CPL 6) Ocean (POP 1.4.3) (1o) Colloquium on Climate and Health 17 July 2006

  8. Why are there multiple Climate Models? • Ongoing research on processes: • The carbon cycle • Interactions of aerosols and clouds • Interactions of climate and vegetation • No “1st principles” theories (yet) for: • Physics of cloud formation • Physics of atmospheric convection • Inadequate data to constrain models Colloquium on Climate and Health 17 July 2006

  9. Brief History of Climate Modeling • 1922: Lewis Fry Richardson • Basic equations and methodology of numerical weather prediction • 1950: Charney, Fjørtoft and von Neumann (1950) • First numerical weather forecast (barotropic vorticity equation model) • 1956: Norman Phillips • 1st general circulation experiment (two-layer, quasi-geostrophic hemispheric model) • 1963: Smagorinsky, Manabe and collaborators at GFDL, USA • Nine level primitive equation model • 1960s and 1970s: Other groups and their offshoots began work • University of California Los Angeles (UCLA), National Center for Atmospheric Research (NCAR, Boulder, Colorado) and UK Meteorological Office • 1990s: Atmospheric Model Intercomparison Project (AMIP) • Results from about 30 atmospheric models from around the world • 2001: IPCC Third Assessment Report • Climate projections to 2100 from 9 coupled ocean-atmosphere-cryosphere models. • 2007: IPCC Fourth Assessment Report • Climate projections to 2100+ from 23 coupled ocean-atmosphere-cryosphere models. Colloquium on Climate and Health 17 July 2006 Slingo

  10. Richardson’s Vision of a Climate Model “Myriad computers are at work upon the weather of the part of the map where each sits, but each computer attends only to one equation or part of an equation. The work of each region is coordinated by an official of higher rank. Numerous little 'night signs' display the instantaneous values so that neighboring computers can read them. Each number is thus displayed in three adjacent zones so as to maintain communication to North and South of the map…” Lewis Fry Richardson Weather Prediction by Numerical Process (1922) Colloquium on Climate and Health 17 July 2006

  11. Evolution of Climate Models Colloquium on Climate and Health 17 July 2006

  12. Basic Equations for the Atmosphere • Momentum equation: dV/dt = -p -2^V –gk +F +Dm • Where =1/ ( is density), p is pressure,  is rotation rate of the Earth, g is acceleration due to gravity (including effects of rotation), k is a unit vector in the vertical, F is friction and Dm is vertical diffusion of momentum • Thermodynamic equation: dT/dt = Q/cp + (RT/p) + DH • where cp is the specific heat at constant pressure, R is the gas constant,  is the vertical velocity, DH is the vertical diffusion of heat and Q is the internal heating from radiation and condensation/evaporation; Q = Qrad + Qcon • Continuity equation for moisture (similar for other tracers): dq/dt = E – C + Dq • where E is the evaporation, C is the condensation and Dq is the vertical diffusion of moisture Colloquium on Climate and Health 17 July 2006 Slingo

  13. Vertical Discretization of Equations Vertical Grid for Atmosphere Colloquium on Climate and Health 17 July 2006

  14. Horizontal Discretization of Equations T31 T42 T85 T170 Colloquium on Climate and Health 17 July 2006 Strand

  15. Physical Parameterizations • Processes that are not explicitly represented by the basic dynamical and thermodynamic variables in the basic equations (dynamics, continuity, thermodynamic, equation of state) on the grid of the model need to be included by parameterizations. • There are three types of parameterization; • Processes taking place on scales smaller than the grid-scale, which are therefore not explicitly represented by the resolved motion; • Convection, boundary layer friction and turbulence, gravity wave drag • All involve the vertical transport of momentum and most also involve the transport of heat, water substance and tracers (e.g. chemicals, aerosols) • Processes that contribute to internal heating (non-adiabatic) • Radiative transfer and precipitation • Both require the prediction of cloud cover • Processes that involve variables additional to the basic model variables (e.g. land surface processes, carbon cycle, chemistry, aerosols, etc) Colloquium on Climate and Health 17 July 2006 Slingo

  16. Parameterized Processes Colloquium on Climate and Health 17 July 2006 Slingo

  17. Momentum Flux Wind Speed 0 ua Processes Included in the CCSM Land Model • The current version includes: • Biogeophysics • Hydrology • River routing • The next version will include: • Natural and human-mediated changes in land cover • Natural and human-mediated changes in ecosystem functions • Coupling to biogeogeochemistry Biogeophysics Hydrology Sensible Heat Flux Latent Heat Flux Photosynthesis Precipitation Diffuse Solar Radiation Longwave Radiation Evaporation Interception Canopy Water Direct Solar Radiation Transpiration Reflected Solar Radiation Emitted Long- wave Radiation Throughfall Stemflow Absorbed Solar Radiation Sublimation Evaporation Infiltration Surface Runoff Snow Melt Soil Heat Flux Soil Water Heat Transfer Redistribution Drainage Colloquium on Climate and Health 17 July 2006

  18. Subgrid Structure of the Land Model Gridcell Landunits Glacier Wetland Vegetated Lake Urban Columns Soil Type 1 PFTs Colloquium on Climate and Health 17 July 2006

  19. “Products” of Global Climate Models • Description of the physical climate: • Temperature • Water in solid, liquid, and vapor form • Pressure • Motion fields • Description of the chemical climate: • Distribution of aerosols • Evolution of carbon dioxide and other GHGs • Coming soon: chemical state of surface air • Space and time resolution (CCSM3): • 1.3 degree atmosphere/land, 1 degree ocean/ice • Time scales: hours to centuries Colloquium on Climate and Health 17 July 2006

  20. The CCSM Program Scientific Objectives: • Develop a comprehensive climate model to study the Earth’s Climate. • Investigate seasonal and interannual variability in the climate. • Explore the history of Earth’s climate. • Estimate the future of the environment for policy formulation. Recent Accomplishments: • Release of a new version (CCSM3) to the climate community. • Studies linking SST fluctuations, droughts, and extratropical variability. • Simulations of last 1000 years, Holocene, and Last Glacial Maximum. • Creation of largest ensemble of simulations for the IPCC AR4. http://www.ccsm.ucar.edu Colloquium on Climate and Health 17 July 2006

  21. The CCSM Community Development Group CCSM3 Atmosphere (CAM 3) NCAR Universities Labs Land (CLM 3) Sea Ice (CSIM 4) Coupler (CPL 6) Physics Applications Chemistry Ocean (POP 1) Model Users Climate Community • Current Users: • Institutions: ~200 • Downloads of CCSM3: • Users:~600 • Publications: • NCAR: 87 • Universities: 94 • Labs/Foreign: 48 • Total: 229 Colloquium on Climate and Health 17 July 2006

  22. Changes in Atmospheric Composition Colloquium on Climate and Health 17 July 2006

  23. Forcing: Changes in Exchange of Energy Colloquium on Climate and Health 17 July 2006

  24. Components of Aerosol Forcing Back Scattering (Cooling) Absorption (Column Warming) Cloud Evaporation (Warming) Absorption (Atmospheric Warming) Cloud Seeding (Cooling) Suppression of Rain; increase of life time (Cooling) Forward Scattering Dimming of Surface Surface Cooling Colloquium on Climate and Health 17 July 2006 Ramaswamy

  25. Simulations of Aerosol Distributions 1995-2000 Colloquium on Climate and Health 17 July 2006

  26. Fidelity of 20th Century Simulations with the CCSM3 • Criteria for the ocean/atmosphere system • Realistic prediction of sea-surface temperature given realistic forcing • Realistic estimates of ocean heat uptakeEffects of ocean on transient climate response • Realism of ocean mixed layer and ventilationOcean uptake of CO2 and passive tracers (CFCs) Colloquium on Climate and Health 17 July 2006

  27. Simulation of Sea-Surface Temperature Colloquium on Climate and Health 17 July 2006

  28. Increases in Global Ocean Temperatures(Results from CCSM3 Ensemble) L = Levitus et al (2005) Ensemble Members Relative Model Error < 25% Colloquium on Climate and Health 17 July 2006 Gent et al, 2005

  29. Global Ocean Inventory of CFC-11(Passive tracer proxy for CO2) } Ensemble Members Data CCSM3 Colloquium on Climate and Health 17 July 2006 Gent et al, 2005

  30. Penetration Depth of CFC-11 WOCE data (Willey et al, 2004) m CCSM3 Simulation Colloquium on Climate and Health 17 July 2006 Gent et al, 2005

  31. Projections for Global Surface Temperature Colloquium on Climate and Health 17 July 2006 Meehl et al, 2005

  32. Projections for Regional Surface Temperature Change Colloquium on Climate and Health 17 July 2006 Meehl et al, 2005

  33. Projections for Global Sea Level Colloquium on Climate and Health 17 July 2006 Meehl et al, 2005

  34. Committed Change:Global Temperature and Sea Level Colloquium on Climate and Health 17 July 2006 Teng et al, 2005

  35. Changes in Sea Ice Coverage Colloquium on Climate and Health 17 July 2006 Meehl et al, 2005

  36. Changes in Permafrost Coverage Colloquium on Climate and Health 17 July 2006 Lawrence and Slater, 2005: Geophys. Res. Lett.

  37. Scientific objectives for the near future • Major objective: Develop, characterize, and understand the most realistic and comprehensive model of the observed climate system possible. • Subsidiary objectives: • Analyze and reduce the principal biases in our physical climate simulations using state-of-the-art theory and observations. • Simulate the observed climate record with as much fidelity as possible. • Simulate the interaction of chemistry, biogeochemistry, and climate with a focus on climate forcing and feedbacks. Colloquium on Climate and Health 17 July 2006

  38. Recent evolution of climate forcing Colloquium on Climate and Health 17 July 2006 Hansen and Sato, 2001

  39. Simulating the chemical state of the climate system Chemistry + BGC + Physics + Ecosystems Emissions Concentrations Forcing Climate Response Feedbacks Feedbacks Chemical Reservoirs Chemical Reservoirs Offline models • In the past, we have generally used offline models to predict concentrations and read these into CCSM. • This approach is simple to implement, but • It cuts the feedback loops. • It eliminates the chemical reservoirs. • The next CCSM will include these interactions. Colloquium on Climate and Health 17 July 2006

  40. CCSM4: a 1st generation Earth System Model Coupler Land Atmosphere Ocean Sea Ice C/N Cycle Dyn. Veg. Land Use IceSheets Ecosystem & BGC Gas chem. Prognostic Aerosols Upper Atm. Colloquium on Climate and Health 17 July 2006

  41. Historical changes in agricultural land use Colloquium on Climate and Health 17 July 2006 Johan Feddema

  42. Changes in surface albedo by land use Colloquium on Climate and Health 17 July 2006 Johan Feddema

  43. Evolution of tropospheric ozone (1890-2100, following A2 scenario) Colloquium on Climate and Health 17 July 2006 Lamarque et al, 2005

  44. Flux of CO2 into the world oceans(Ocean ecosystem model) Colloquium on Climate and Health 17 July 2006 Moore, Doney, and Lindsay

  45. Conclusions • Modern climate models can be applied to: • Studying the integrated climate system • Modeling climates of the past • Projecting future climate change and its impact • Challenges ahead for modelers: • Process-oriented modeling of the climate • Coupled chemistry/climate modeling • Challenges ahead for the community: • Better linkages between modelers, health specialists, & policy makers • Better modeling of chemical and biological climate change Colloquium on Climate and Health 17 July 2006

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