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Announcements. All recent lab quizzes up front Makeup for all labs is next week (April 22 and 24) – Please e-mail me and remind me if you need to make up a lab; bring documentation The “quiz” for this week’s lab = take home assignment. Intergovernmental Panel on Climate Change (IPCC). - PowerPoint PPT Presentation
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AnnouncementsAll recent lab quizzes up front
Makeup for all labs is next week (April 22 and 24) –
Please e-mail me and remind me if you need to make up a lab; bring
documentation
The “quiz” for this week’s lab = take home assignment
Intergovernmental Panel on Climate Change (IPCC)
• All countries that are members of UN can have scientists participate
• Scientists from many areas of expertise:– Read scientific literature (papers) – Compile and analyze the data– Make future predictions of climate change
IPCC Reports
1990 First Assessment Report (FAR)
1996 Second Assessment Report (SAR)
2001 Third Assessment Report (TAR)
2007 Fourth Assessment Report (AR4)
Today we will look at results from 2007 (average change) and 2001 (Sphere models)
Predicted Average Global Temperature Change
• From 2007 IPCC report
• Red, green, blue are three different model results
• This is averaged over the entire Earth!
Global Circulation Models (GCMs)
• How are GCMs made?
• Should you believe everything that comes out of a computer?
• Results– Average global temperature increase– Regional temperature changes
Global Circulation Models (GCMs)
• Are physical climate models• Based on our understanding of physics,
chemistry, biology of different parts of climate
• 3 different models today – made by 3 different groups of scientists for IPCC– GFDL – CCSM – UKMET
Running a GCM model
IPCC Models: Step 1 Input
• Forcings: things that are going to change climate
Human activity
IPCC models: Step 1 Input
• Greenhouse gases, including human input– Increase to 720 ppm CO2 by 2080
– Pre-industrial: 280 ppm CO2
– Today: 380 ppm CO2
• Sulfate aerosol concentrations and volcanic aerosols
• Changes in sunlight reaching Earth
• Changes in ozone
Running a GCM model
IPCC Models: Step 2 Climate Simulation
• Internal interactions
Human activity
Structure of a General Circulation Model
• Each subsystem modeled separately
• Link subsystems together with a “coupler” program– Example: interaction
between atmosphere and oceans
http://www.ccsm.ucar.edu/models/ccsm3.0/
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Running a GCM model
IPCC Models: Step 3 Results
• Internal responses
Human activity Temperature
Model Resolution
• See more detail with higher resolution!
• But higher resolution takes more computer power
Higher resolution
(Smaller block size)
Lower resolution
(Larger block size)
GCM resolution
Vertical Layers
• Split oceans, land, atmosphere into blocks
• Grid: size of blocks• Grids are different
sizes in different models
• Grids are not always uniform (different block sizes)
Example of a grid at the surface of the ocean
1 degree longitude isn’t same distance everywhere
http://academic.brooklyn.cuny.edu/geology/leveson/core/linksa/lat_long.html
Numerical problems with poles!
• The distance between longitude grid spacing goes to zero at poles
• Computers can’t handle this
• Models deal with this for oceans by shifting the entire grid (North Pole on a continent) or by inventing a new land mass!
http://academic.brooklyn.cuny.edu/geology/leveson/core/linksa/lat_long.html
Change the grid
http://climate.lanl.gov/Models/POP/images/tripolegrid.jpg
To the sphere!
Is the computer model right?
1. Different models by different groups should give similar results
2. Higher resolution should give better results
3. The results of the model should not be influenced by the way the model is constructed
Is the computer model right?
• Must make assumptions
• Don’t understand everything about physics and chemistry of climate
• Difference between reality and possibility
• Should we follow the model’s predictions even if they might not come true?