CLIM 690: Scientific Basis of Climate Change Climate Models and Their Evaluation

CLIM 690: Scientific Basis of Climate Change Substitute for reality Closely mimics some essential elements Omits or poorly mimics non-essential elements What is a Model?

CLIM 690: Scientific Basis of Climate Change Quantitative and/or qualitative representation of natural processes (may be physical or mathematical) Based on theory Suitable for testing “What if…?” hypotheses Capable of making predictions What is a Model?

CLIM 690: Scientific Basis of Climate Change What is a Model? Input DataModelOutput Data Tunable Parameters What output data might we consider for a typical climate model? What input data might we consider for a typical climate model? What are the tunable parameters of interest?

CLIMATE DYNAMICS OF THE PLANET EARTH S Ω a g T4T4 WEATHERWEATHER CLIMATE. CLIMATE. hydrodynamic instabilities of shear flows; stratification & rotation; moist thermodynamics day-to-day weather fluctuations; wavelike motions: wavelength, period, amplitude S,, a, g, Ω O 3 H 2 O CO 2 stationary waves (Q, h*), monsoons h*: mountains, oceans (SST) w*: forest, desert (soil wetness)  (albedo)

CLIM 690: Scientific Basis of Climate Change Example of a Model: Earth’s Energy Balance THEORY: Energy conservation: Change in energy due to difference in fluxes Solar Radiation S = 1380 Wm -2 (plane, parallel) Planetary Emission

CLIM 690: Scientific Basis of Climate Change Example of a Model: Earth’s Energy Balance THEORY: Energy conservation: Change in energy due to difference in fluxes MODEL: Assume radiative equilibrium INCOMING FLUX = OUTGOING FLUX (1 -  ) S (  a 2 ) = Q e (4  a 2 ) Q e = 1/4 (1 -  ) S Measured albedo (  ) = 0.31 Measured planetary Q e = 237 Wm -2 Blackbody temperature (  T 4 law): 254 K Measured surface Q es = 390 Wm -2 Blackbody temperature (  T 4 law): 288 K Atmosphere absorbs 153 Wm -2 Greenhouse effect: 34 K Solar Radiation S = 1380 Wm -2 (plane, parallel) Planetary Emission

CLIM 690: Scientific Basis of Climate Change Equations of motions and laws of thermodynamics to predict rate of change of: T, P, V, q, etc. (A, O, L, CO 2, etc.) 10 Million Equations: 100,000 Points X 100 Levels X 10 Variables With Time Steps of: ~ 10 Minutes Use Supercomputers What is a Climate Model?

CLIM 690: Scientific Basis of Climate Change Model Complexity: Development of Climate/Earth System Models

CLIM 690: Scientific Basis of Climate Change

Model Complexity: Development of Climate/Earth System Models

CLIM 690: Scientific Basis of Climate Change

Model Complexity: Development of Climate/Earth System Models

Ultimate: all physico-biogeochemical Earth System

CLIM 690: Scientific Basis of Climate Change Validation –Confirmation that formulation of model conforms to intent (equations, algorithms, units, specified parameters etc.) –Confirmation that outputs are, within tolerable limits, as expected for given inputs Verification –Comparison with known, measured (observed) quantities –Means, variability (frequency, amplitude, phase) –Spatial structure (scale, shape, amplitude) –Simulation: confirms theory for specified circumstances (e.g. specified boundary conditions) –Prediction: accurately reproduces time series of observed evolution from specified initial conditions (Inter-)Comparison –Comparison among different models’ outputs for identical inputs What is Model Evaluation?

CLIM 690: Scientific Basis of Climate Change Example: ENSO Prediction –Comparison of many salient characteristics of ENSO with observations and among models –Coupled ocean-atmosphere models with specified, observed initial conditions and external forcing (e.g. GHG concentrations) What is Model Evaluation?

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics SST along the equator Annual MeanDifference from Observations

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics SST along the equator in the Pacific (mean annual cycle) - lead time 1-3 months

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics SST along the equator in the Pacific (mean annual cycle) - lead time 4-6 months

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics Standard DeviationDifference from Observations

CLIM 690: Scientific Basis of Climate Change (a) (b) (c) Jin et al Climate Dynamics RMSEInterannual Variability Intra-ensemble Variability Annual Cycle Error Intra-ensemble Variability

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics Correlation Forecast Lead (months)

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics Correlation Forecast Lead (months)

CLIM 690: Scientific Basis of Climate Change Jin et al Climate Dynamics Correlation Forecast Lead (months)

CLIM 690: Scientific Basis of Climate Change Evaluating the IPCC Models

CLIM 690: Scientific Basis of Climate Change

Figure 8.2 OBS (contours) & mean MME error (shades) SST ( ) SAT ( ) MME RMS error

CLIM 690: Scientific Basis of Climate Change Figure 8.3 SST & SAT st. dev. OBS (contours) & mean MME error (shades)

CLIM 690: Scientific Basis of Climate Change RMS error w.r.t. ERBE mean error in SW  TOA mean error in OLR

CLIM 690: Scientific Basis of Climate Change OBS Annual Mean Precipitation MME

CLIM 690: Scientific Basis of Climate Change Climate Model Fidelity and Projections of Climate Change J. Shukla, T. DelSole, M. Fennessy, J. Kinter and D. Paolino Geophys. Research Letters, 33, doi /2005GL025579, 2006