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Examining the Effects of Global Warming on Greenland |
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Outreach -
Exercises
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Written by Mark Chandler
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Sunday, 11 December 2005 |
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Science Summary
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EdGCM Exercise
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Educational Perspective
 Figure 1. The EdGCM Toolbar showing the global warming run selected. Use the Play button to run this experiment from the standard install of EdGCM
 Figure 2. You can use the Trend menu in EdGCM and EVA to plot the CO2 trend used in this run (figure 2). Titles, line color, etc. can be adjusted by the user. This trend was created using the trend section in EdGCM�s Setup Simulations window. The trend is hypothetical, not observed, but it does have a similar character to the current trend of atmospheric carbon dioxide and the forcing projected from this trend is similar to 20th century observations and is within the range of Intergovernmental Panel on Climate Change (IPCC) estimates for the coming decades.
First, run the experiment Global_Warming_01 (figure 1), which simulates the effects on climate of increasing carbon dioxide during the years 1958 through 2100.
Next use EdGCM's Analyze Output window to generate 5 year averages of the years 1958-1962, 2000-2004, and 2058-2062. In the Maps tab select Snow Coverage, Snow Fall, Snow Depth, and Surface Air Temperature then extract those variables into viewable files by clicking the "Get Maps" button. Using EVA's data browser, make two difference maps (i.e. anomaly maps) for each variable:
2000,04avg - 1958,62avg
2058,62avg - 1958,62avg
This will result in the 8 separate images, like those shown in figure 4 - 11, below. The setup of the EVA toolbar is shown in figure 3. Make sure to choose an appropriate (but symmetric) scale range for each variable since the -5 to 5 range, shown in figure 3, only applies to the SurfAirTemp variable.
 Figure 3. Set up EVA's toolbar like this to make maps similar to those seen in this guide. Scientific Results
Examining the simulated variables shows that surface temperatures have risen over Greenland already by the 2004 time frame (fig. 4). Furthermore, the snow fall rate increase by 2004 (fig. 5) strongly supports the data findings that in a warming climate the snow fall over Greenland can increase. Further analysis shows that the snow depth has also increased slightly in the interior (fig. 6) in accordance with new scientific observations, though not as much as the data would suggest. This indicates, perhaps, that the GCM Global Warming simulation is not capturing exactly the features of the Earth's current climate change. Examining the snow cover (fig. 7) also shows that snow cover can increase slightly in a warmer climate, but the pattern of increase is unique from that of the snow depth.
Using the GCM simulation to explore the eventual effect of increasing CO2 on Greenland's climate shows that as temperatures continue to rise (fig. 8), snow fall rates in the interior of Greenland also continue to be greater than 20th century values. However, snow depth and snow cover (figures 9 and 10) show that the increased rate of snow fall cannot keep pace with the increased melting and thus both snow depth and snow cover would be expected to decrease as global warming proceeds into the mid-21st century.
The implication is that, although the new scientific observations show an increase in the elevation of the interior Greenland ice sheet, the ultimate impact of Global Warming will be a reduction in the size of the ice sheet and, consequently, a rise in sea level. Should the entire Greenland ice sheet melt, sea levels would be expected to rise about 7 meters.
Figures 4-7
Climate Change from the Period 1958-62 to 2000-04
 Figure 4  Figure 5  Figure 6  Figure 7 Figures 8-11
Climate Change from the Period 1958-62 to 2058-62
 Figure 8  Figure 9  Figure 10  Figure 11
Science Summary
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EdGCM Exercise
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Educational Perspective
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