Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
What is a climate model?
If we cannot predict weather, how can we predict climate?
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Reading for Week 6Lecture 11
What is a climate model?
• RG 227-244• GW Chapter 5• IPCC WG1 Chapter 8, FAQ 8.1 How Reliable Are the
Models Used to Make Projections of Future Climate Change? – ftp://iges.org/pub/emilia/CLIM101_2010/reading/
IPCC_WG1_FAQ8.1.pdf
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
• Substitute for reality• Closely mimics some
essential elements• Omits or poorly
mimics non-essential elements
What is a Model?
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
What is a Model?
• 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
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Input Data Model Output 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?
What is a Model?
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Input Data Model Output Data
Tunable Parameters
What is a Model?
• Temperature, Pressure, Humidity, Wind Velocity, Salinity, Ice Mass, …
• Averaged by Day, Month, Season, Year, …
• Need verification with obs
• Energy flux from Sun• Atmospheric
constituents (CO2, etc.)
• Landscape features (geography, topography, land use, etc.)
• Initial conditions of all predicted variables
Properties of:Clouds, Ice, Aerosol …
CLIMATE DYNAMICS OF THE PLANET EARTH
S
Ω
a
g
T4
WEATHER
CLIMATE .
hydrodynamic instabilities of shear flows; stratification & rotation; moist thermodynamics
day-to-day weather fluctuations; wavelike motions: wavelength, period, amplitude
T_
y,U_
yT_
z,U_
z
S, , a, g, ΩO3
H2OCO2
stationary waves (Q, h*), monsoons
h*: mountains, oceans (SST)w*: forest, desert (soil wetness)
(albedo)
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
(approximation)
Mass conservation
Energy conservation
Newton’s law
= p / ps
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Equations of motions and laws of thermodynamics predict rate of change of:
T, P, V, q, etc. (A, O, L, CO2, etc.)
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Equations of motions and laws of thermodynamics predict rate of change of:
T, P, V, q, etc. (A, O, L, CO2, etc.)
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Discretization
Atmosphere and ocean are continuous fluids … but computers can only represent discrete objects
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Discretization
Atmosphere and ocean are continuous fluids … but computers can only represent discrete objects
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
• Equations of motions and laws of thermodynamics to predict rate of change of:
T, P, V, q, etc. (A, O, L, CO2, etc.)
• 10 Million Equations: 100,000 Points × 100 Levels × 10 Variables
• With Time Steps of: ~ 10 Minutes
• Use Supercomputers
What is a Climate Model?
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Numerical Weather Prediction
1. Determine (continuous) equations to be solved– Equation of state or Ideal Gas Law (Boyle’s Law relates P V, Charles’
Law relates V T, Gay-Lussac’s Law relates T P)– Conservation of mass (dry air, water)– Conservation of energy– Conservation of angular momentum– Result: set of coupled, nonlinear, partial differential equations
2. Discretize the equations for numerical solution (typically requires computer)
3. Measure current state of global atmosphere to obtain initial conditions
4. Solve the initial value problem to produce a forecast5. Take into account uncertainty in measured atmospheric state by
repeating step 4 over an ensemble of slightly different initial conditions
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Climate Predictability: Averages in space and/or time are more predictable than instantaneous values.
Energy balance sets the range of weather variation.
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Science
Predictability in the Midst of Chaos: A Scientific Basis for Climate
Forecasting23 October 1998, Volume 282, pp. 728-731
J. Shukla
Soil Wetness
SST Anomalies (oC)
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
1998 JFM SST [oC]
JFM SST Climatology [oC]
1998 JFM SST Anomaly [oC]
El Nino/Southern Oscillation
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
El Nino/Southern Oscillation
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Rainfall Anomalies
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
ca 2000AGCM
Model Simulation of ENSO Effects500 hPa Height Anomalies (ACC = 0.98)
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Moore’s “Law”
IPCC-1
IPCC-2
IPCC-3
IPCC-4
103-fold jump since 1st IPCC106-fold jump in last 30 years
Latest advance due to dual-core chipsNear-term advance w/quad-core chips
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Johnvon Neumann
Seymour Cray& Cray-1
ENIAC
IBM 360
Cray-2
ColumbiaNASA
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Climate Models circa early 1990s Global coupled climate models in 2007 and new ESMs
New decadal prediction modelsGlobal coupled models in 5 yrs post-AR5
~500 km ~100 – 200 km
~50 km ~10 km
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
European Heat Wave 2003
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
JJA 2003 SST Anomaly
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
JJA obs
OBS.SST-CLIM.SST exp. result significant at more than 90% sig.lev.
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
J. Shukla, T. DelSole, M. Fennessy, J. Kinter and D. PaolinoGeophys. Research Letters, 33, doi10.1029/2005GL025579, 2006
Climate Model Fidelity and Projections of Climate Change
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Regional Climate Change – Beyond Today’s Models’ Ability?
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Annual Mean Precipitation ChangeEurope: 21st C minus 20th C
T159 (125-km) T1279 (16-km)
“Time-slice” runs of the ECMWF IFS global atmospheric model with observed SST for the 20th century and CMIP3 projections of SST for the 21st century at two different model resolutions
The continental-scale pattern of precipitation change associated with global warming is the same, but the regional details are quite different, particularly in southern Europe.
Center of Ocean-Land-Atmosphere Studies CLIM101: Global Warming - Weather, Climate and Global Society
Summary1. Weather prediction depends on initial conditions (global
observations).
2. Short-term climate (seasonal-decadal) depends on boundary conditions (SST, soil wetness, snow, sea ice, etc.), which depends on ocean-atmosphere interactions.(natural forcings: sun, volcanoes, etc.)
3. Long-term climate change depends on “external” forcing (Human: greenhouse gases, land cover change, etc.)