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There is a great deal of attention placed on climate change and global warming. It is widely accepted in the scientific community that humans are causing global temperature increases because of the "greenhouse effect". This effect is due to the release of excess carbon dioxide (CO2), among other gases, into the atmosphere primarily through the burning of fossil fuels. These gases act as a greenhouse by shielding Earth's outgoing long-wave radiation which get trapped in the atmosphere.
The chart below lists several other greenhouse gases and their human sources. Interestingly, CFC's which contribute to the destruction of the ozone hole have been on the decline in the atmosphere ever since 24 countries signed the Montreal Protocol which phased out the use of CFC's over several years. The reduction in CFC's has allowed for re-growth of the stratospheric ozone layer which protects us from harmful UV radiation. This is a great example of how humans can overcome significant global problems.
But what about other gases? Much focus is placed on CO2 which has been shown to be directly linked to temperature.
Above is a drawing of what Antarctica would look like after all of the ice melted. As you can see most of the ice on the West Antarctic Ice Sheet is actually grounded below sea level.
Table 1.1
| Total volume of Ice = 2.6 x 106 km3 in Greenland, 29.3 x 106 km3 in Antarctica |
| Total Ocean Surface Area = 36.1 x 106 km2 |
| Density of Water = 1000 kg m-3, or = 1 x1012 kg km-3 |
| Density of Ice = 900 kg m-3, or = 9 x 1011 kg km-3 |
In the movie Waterworld, global warming had progressed to the point where all of the ice on the earth had melted leaving a vast sea covering all of the land. While the consequences of global warming are not that drastic there are some serious consequences to face if all of the ice melted.
1. With the statistics given in Table 1, above, calculate the amount of sea level rise that would occur if all of the ice on the earth melted. Remember that no mass is lost as ice coverts to water, however there is a density change. You'll need to first get a water equivalent volume that the ice would produce.
2. From your calculations do you think that Central Canada will become an "oasis" of land in the middle of a large sea or will we be inundated with water. What about southern Florida?
3. There are some uncertainties in the simple calculation above. What do you think some of them would be? Remember, that the oceans don't have vertical walls.
Critics of global warming theories sometimes use the following analogy as an argument against the possibility of sea level rise:
The relationship between glacial ice and sea level is analogous to a drinking glass filled with ice cubes and water. If the ice in the glass melts, the amount of liquid in the glass increases but the total volume of water in the glass remains the same, since the glass does not overflow. Similarly, glacial ice melting merely represents a change of state. No new water is created so there should be no increase in sea level.
4. Do you agree with this statement? Why? How does this explain why the volume of ice in the Arctic Sea wasn't included in the calculation of #1. (Think about the location of glaciers/ice sheets relative to the oceans.)
There are a number of reasons to be cautious in predictions of the effects of global warming. In fact, one of the current theories predicts that with increased global warming only Arctic ice will melt because the temperature of Antarctic ice is so cold that any increase in temperature still would not melt it significantly. It is thought that Antarctica will instead experience a greater amount of snowfall (as the atmosphere warms up enough so that it can carry more moisture) possibly leading to an actual advancement of glaciers in the southern hemisphere.
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