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

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

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

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

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

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

Colloquium on Climate and Health 17 July : 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 –1 st 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 from 23 coupled ocean-atmosphere-cryosphere models. Brief History of Climate Modeling Slingo

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

Colloquium on Climate and Health 17 July 2006 Momentum equation: dV/dt = -  p -2  ^V –gk +F +D m 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 D m is vertical diffusion of momentum Thermodynamic equation: dT/dt = Q/c p + (RT/p)  + D H where c p is the specific heat at constant pressure, R is the gas constant,  is the vertical velocity, D H is the vertical diffusion of heat and Q is the internal heating from radiation and condensation/evaporation; Q = Q rad + Q con Continuity equation for moisture (similar for other tracers): dq/dt = E – C + D q where E is the evaporation, C is the condensation and D q is the vertical diffusion of moisture Basic Equations for the Atmosphere Slingo

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

Colloquium on Climate and Health 17 July 2006 Horizontal Discretization of Equations T31T42 T85T170 Strand

Colloquium on Climate and Health 17 July 2006 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; 1.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) 2.Processes that contribute to internal heating (non-adiabatic) Radiative transfer and precipitation Both require the prediction of cloud cover 3.Processes that involve variables additional to the basic model variables (e.g. land surface processes, carbon cycle, chemistry, aerosols, etc) Physical Parameterizations Slingo

Colloquium on Climate and Health 17 July 2006 Parameterized Processes Slingo

Colloquium on Climate and Health 17 July 2006 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 Drainage Hydrology Canopy Water Evaporation Interception Snow Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Soil Water Redistribution Direct Solar Radiation Absorbed Solar Radiation Diffuse Solar Radiation Longwave Radiation Reflected Solar Radiation Emitted Long- wave Radiation Sensible Heat Flux Latent Heat Flux uaua 0 Momentum Flux Wind Speed Soil Heat Flux Heat Transfer Photosynthesis Biogeophysics Processes Included in the CCSM Land Model

Colloquium on Climate and Health 17 July 2006 Subgrid Structure of the Land Model Gridcell GlacierWetlandLake Landunits Columns PFTs UrbanVegetated Soil Type 1

Colloquium on Climate and Health 17 July 2006 “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 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.

Colloquium on Climate and Health 17 July 2006 The CCSM Community Atmosphere (CAM 3) Ocean ( POP 1) Coupler (CPL 6) Sea Ice (CSIM 4) Land (CLM 3) CCSM3 Model UsersClimate Community Development Group NCARUniversitiesLabs PhysicsApplicationsChemistry 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 Changes in Atmospheric Composition

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

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

Colloquium on Climate and Health 17 July 2006 Simulations of Aerosol Distributions

Colloquium on Climate and Health 17 July 2006 Fidelity of 20 th 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 uptake Effects of ocean on transient climate response –Realism of ocean mixed layer and ventilation Ocean uptake of CO 2 and passive tracers (CFCs)

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

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

Colloquium on Climate and Health 17 July 2006 Global Ocean Inventory of CFC-11 (Passive tracer proxy for CO 2 ) Gent et al, 2005 Ensemble Members } Data CCSM3

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

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

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

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

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

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

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

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

Colloquium on Climate and Health 17 July 2006 Simulating the chemical state of the climate system Emissions Chemistry + BGC + Physics + Ecosystems Chemical Reservoirs ConcentrationsForcing Climate Response Feedbacks 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. Offline models Feedbacks Chemical Reservoirs

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

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

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

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

Colloquium on Climate and Health 17 July 2006 Flux of CO 2 into the world oceans (Ocean ecosystem model) Moore, Doney, and Lindsay

Colloquium on Climate and Health 17 July 2006 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