To start off today, the students reviewed what they had done yesterday, and continued the focus on global warming. The students conducted an experiment using the atmospheric model they used yesterday (http://geosci.uchicago.edu/~archer/cgimodels/radiation.html). They also students tried, using the average gas mileages from their family cars, to find out how much Carbon Dioxide (CO2) their family put into the atmosphere per year. They found that the instructor's Hybrid Toyota Prius puts 4.2 TONS of CO2 into the atmosphere annually and a Cadillac Seville, that gets about 15 miles per gallon, put almost 15 tons of CO2 into the atmosphere annually.
Some students knew that the 'factories' for getting rid of Carbon Dioxide were trees. However, to find out how much CO2 the tree gets rid of, or sequesters, you need to know how much it weighs. But how do you weigh a tree without taking it out of the ground? The students used a Carbon Dioxide Sequestration Calculator using the height of the tree, circumference, moisture ratio, and its type (Southern Pine Coastal Plain, Southern Pine Piedmont, Hard Hardwood, Soft Hardwood, Sweet Gum or Yellow Poplar). Since it was raining, the students went to go see the tree that the instructor had measured, and weighed previously. Afterwards, they examined a map of predicted global warming, and hypothesized why certain areas would get warmer than others.
The students viewed a graph of the global mean surface air temperature from the NOAA. The graph showed that before the industrial age, temperatures fluctuated, but stayed within a certain range. At about the beginning of the 20th century, the temperature and CO2 levels both began to rise. The levels of each coincided very closely. If you were to continue the graph, the temperature would rise quite significantly. There are other danger signs, too; such as the sea ice at the North Pole getting thinner. If the amount of CO2 quadruples, which is possible if humans don't put major conservation programs into effect, the ice could melt completely at many areas, or be thin at all of the other places. Also a quadrupling of CO2 would cause a jump in sea level of 1.5 meters (about 5 feet), which could flood some of NC's Outer Banks, as well as the Everglades. The students also used Stella (a program for viewing and editing computer models) to view a computer model of the variables that affect water temperature. Another more complicated model took into effect more variables such as CO2 levels. The Stella program also shows graphs.
They researched the state of carbon stocks, the amount of carbon sequestered by trees, versus the amount re-released into the atmosphere by the rotting of the trees. Forests that are harvested have carbon stocks that fluctuate rapidly, but if a forest is never in a state of flux, its carbon stocks are steadier. The average American forest will soon reach its peak of carbon stocks, while the average Canadian forest has already reached its peak.
To wind up today's lesson, the students talked about methods to conserve and reduce CO2, such as the Kyoto Protocol, and how it gives incentives to countries to manage forest well to offset Carbon Dioxide emissions.