Part 5—Generate Snow and Ice Coverage Maps

Note: If this is a new session with EdGCM, you will need to complete Steps 1-3 below. If you already have the program running you can move directly to Step 4.

Step 1 – Launch EdGCM

1. Launch EdGCM by double clicking on the icon in the EdGCM folder, the application will load. The toolbar window will appear. This toolbar window is the controller for the software. The buttons will change depending on your active window.
2. In this window, choose Modern Predicted SST in the toolbar Run List. This is the baseline for the model. In this simulation scientists have used climatic conditions from 1958 in order to demonstrate the future climate trends with no increase in greenhouse gases or other variables such as solar luminosity. This is the baseline, or control, for comparison to the climate change runs.

Step 2 – Generate a Map

1. Launch the Analyze Output feature of the EdGCM, by clicking on the button on the top of the toolbar. Or use the drop down window menu.
2. Click on the maps tab.

Step 3 – Prepare Output for Analysis

1. On the left hand side of the Analyze Output window, choose the last five years by clicking on the last 5 button. Alternately, manually select the years of your choice. Note: Using a group of five or more years helps to smooth out some variables that may differ a lot from year to year.
2. Once the years have been selected, click the Average button at the bottom of the list. This creates an average of all variables from the last 5 years of the simulation. A window opens as the files are "post-processed". This step may take up to a minute to complete. Note: if this step has already been completed the button may be grayed out (in-active).
3. In the center section of the Analyze Output window select from the following variables by clicking on the checkbox next to each; 
   
   • snow and ice coverage
   • precipitation
   • evaporation
   • low level cloud coverage
   • surface air temperature (in C)
   • max surface air temperature (in K)
4. Check the Monthly Seasonal and Annual check boxes at the bottom of the Analyze Output window.
5. Click on Extract button, you will see a window open, which shows that another post-processing program is running.
6. Under View Images Select the 2096-2100ij.nc file, then click the View button at the bottom right of the window.
7. Repeat numbers 2-6 from above for IPCC_A1FI_CO2 simulation.

Show me how to get the IPCC file

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Step 4 – Generate Snow and Ice Coverage Maps

1. In EVA Data Browser window, hold down the shift key and select both the Modern Predicted SST and the IPCC_A1FI_CO2 scenarios in the upper left file window. Then select Snow and Ice Coverage in the center and Dec,Jan,Feb in the right column. Both files will appear in the lower bottom file pane in the order that you generated them. 
    
2. Click the Plot All button. The software will generate two maps: 
   Modern_PredictedSST Snow and Ice Coverage and IPCC_A1FI_CO2 Snow and Ice Coverage. 
    
3. The maps need to be interpolated, or smoothed. To do this click the "interpolate" check box in the toolbar next to each map (it is near the top of the toolbar).
   Show me more about what it means to interpolate.
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   Interpolation is a method of smoothing data points. According to the Merriam Webster Dictionary, "It allows one to estimate values of (data or a function) between two known values."

Step 5 – Finalize the Maps

1. Click on the Projection menu under map heading in on the toolbar. Use the pulldown menu to change the projection to Mollweide.
   Show me more about map projections.
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   Mollweide map projections are a type of equal-area map where the central meridian and latitude lines are straight. They are generally used for global maps. The advantage of this type of projection is that it accurately portrays area while distorting shape and direction. Each type of map projection distorts one or more of these variables, and no projection accurately portrays them all.
2. Note the range shown on the Colorbar /scale is now in percentage coverage, with 100% coverage the most complete and 0% the least.
3. Change the Colorbar / scale to haxby.pa1
4. Add overlay modern with USA for both maps. Explore other overlay options.
5. Save your maps for future reference. Give them a unique name that describes them.
6. Answer the following questions about your maps:
   • In your mind, what is 100% snow coverage?
   • Compare the two maps; in what regions of the Earth do you see the greatest change in snow coverage?

Step 6 – What Effect will Climate Change have on Snow and Ice Coverage?

1. Repeat the steps you used in Part 3 to generate a differencing map, only this time use the snow ice coverage maps.
   Show me how
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   In EVA's Data Browser, subtract the control run, Modern_predictedSST, from the climate change experiment (IPCC_A1FI_CO2) using the differencing drop down menu.
   

   Show me another method

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   Another method to do differencing is to right-click (PC) or control-click (Mac) on the IPCC_A1FI_CO2 map that you just generated. In the menu that appears, choose differencing and me- X (IPCC_A1FI_CO2 – modern predictedSST).
2. Edit the map colorbar / scale to emphasize the change of snow and ice coverage.
   • Check the "flip" checkbox.
   • Adjust the range of the colorbar / scale to a maximum of 10 and a minimum of -30.
3. Save your map for further reference. When you save the map rename it with a name that describes the map, such as "snow coverage map."
4. Once you have completed the maps answer the following questions:
   • How much will the snow coverage decrease by 2100 according to the model?
     Show me the answer
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     The range will be between 10 and 30 percent, depending on the area you are looking at.
   • How does this trend compare to the trends seen in satellite observations of changes in North American snow coverage? See NSIDC State of the Cyrosphere for more information, maps and graphs.
   • Snow is an important part of nature's water storage system. How will climate change impact water resources in the United State? Read the full report Water Resources.
   • The snow and ice covered regions of the Earth are known as the cyrosphere. These regions are important to the entire world's population. Not only do they supply recreation and fresh water, for drinking ans irrigation, they also help to moderate the temperature of the planet. To learn more about the cyrosphere consult the National Snow and Ice Data Center.