Q: How are ozone depletion and global warming related?
A: Both are human-caused global environmental problems, and both are due to the release of man-made gases.  Aside from that, essentially, ozone depletion and global warming are unrelated problems. Global warming is due to anthropogenic enhancement of the greenhouse effect.  Humans have significantly increased the amount of carbon dioxide in the atmosphere via the burning of fossil fuels and destruction of biomass.  Stratospheric ozone depletion is caused by chemical reactions involving anthropogenically produced chlorine compounds, chlorofluorocarbons (CFCs).
    However, as we have discussed in the course, many phenomena in the Earth system are intertwined with one another via feedbacks and couplings.  The most obvious connection between ozone depletion and global warming is the presence of CFCs.  CFCs are the principle cause of ozone deletion, but they also happen to be greenhouse gases.  However, because of their relatively low concentrations in the atmosphere, CFCs are responsible for less than 10 percent of total atmospheric warming.  Carbon dioxide is a far more important greenhouse gas, thought to account for over 60 percent of global warming.  In short, even though they are greenhouse gasses, CFCs are more important in their role in ozone depletion.  
    A less obvious connection between global warming and the hole in the ozone layer is currently under scientific investigation.  It seems that increases in the concentration of greenhouse gasses, while they lead to warmer temperatures on the Earth's surface, can actually lead to cooler temperatures in the stratosphere.  This cooling is from the fact that stratospheric carbon dioxide radiates more energy out to space.
Cooler stratospheric temperatures would contribute to more high clouds over the Antarctic.  These clouds could in turn create conditions that favor ozone-destroying chemical reations.

Q: Does the chemical makeup of the atmosphere affect the amount of light reflected from a planet or moon? Does it affect the color? Mars is the "red planet," and it's light does indeed look red - is that because of the red soil or because of gases in the atmosphere?
A: The chemical composition of the atmosphere of a planet can indeed affect its color, especially when you are on the planet.  For example, on Earth the sky is blue because the size of the most abundant molecules (N2 and O2) is similar to the wavelength of blue radiation, such that blue radiation will be scatterred preferentially to the longer wavelengths (yellow and red).  What we see is thus a blue sky.  If you were to go on the moon and looked up, the sky would be black: there is no atmosphere, and thus you will see space which does not emit visible radiation.  The 'red' color of Mars (as seen from Earth) comes from the minerals that are on the surface of Mars.  These minerals tend to be of a reddish color.  Mars' atmosphere is rather 'thin' such that it won't affect the color of Mars directly.

Q: Could the Daisyworld example be an actual true scenario on Earth. Reflectivity decreases heat?
A: This is an intriguing problem that researchers have been wondering about.  Could it be that at some point in Earth's history temperature was so low that the oceans partially froze over? Because of the positive feedback between temperature and ice coverage, the increased reflectivity of the Earth would lead to colder temperatures, and more ice would form. Eventually, the Earth would be totally covered with ice, leading to what is called a "Snowball Earth". Would life be possible in such an environment? How could the ice ever melt? These questions are still controvertial in the scientific community, and will be discussing the case of "Snowball Earth" in class in a few weeks. Stay tuned!

Q: Are the homework assignments graded on completion or on the amount of questions that were answered correctly?
A: The homework assignments will be graded based on the number of correct answers. The quizzes will be graded on completion: if you submit the answers to the quiz within 24 hours after is it posted you get full credit (regardless of whether you get the right answers), if you submit it later than that but still within 72 hours of posting you will get half credit for the quiz.

Q: When do I need to let you know if I wish to have this class count towards a W course? And if I choose to, would it still also count towards NW? 
A: You can let me know at the time you turn in your research paper (which should be 2,500 words long instead of 1,000). Simply write "W" on the front page of your paper.  If you choose to take this class to fulfill your "W" (writing) requirement, you will get FIVE "W" credit and FIVE natural sciences credits.  You will thus get both credits, but they will fulfill different requirements.

Q: Will our grades/scores ever be posted on the net so that we may know as to what our current grade in the class is?
A: We will not post your grades on the web, but you can ask Amy (the T.A.) and shell will be happy to let your know what your current grade is at any point.
 

 Last Updated:
10/04/2001