Day 1
- Set up week 12 notes
- Discuss Quiz 6. Just about everyone made the same mistake with significant digits: the number $.00850$ has 3 significant digits, not 4 or 2. Just about everyone seems to get that nonzero digits are always significant -- so the 8 and the 5 are definitely significant, so there are at least two sig. digits in the question. The difficulty is with the zeros -- sometimes zeros are significant, sometimes they aren't. So which zeros are significant here?
The zero at the end is significant, because writing it down, at the end of a number after a decimal point, indicates that you measured the given number with a precision that includes the ten-thousandths place. You didn't round to get that zero, you actually measured it. Any rounding occurred at even smaller digits. So with the 8 and the 5, that gives 3 significant digits.
Which means that the two leading zeros don't count. Why not?
One way to think about those zeros is to write the number in scientific notation, which would be $8.50 \cdot 10^{-3}$, which has three digits in it. Why didn't you write the leading zeros down? Because they are part of the exponent in the scientific notation version. Those zeros are about the magnitude of the number, not its value. Thus they don't count.
- We're going to move on from the 1880-2006 global climate data set to look at data from a much larger time scale -- 400,000 years. How could you possibly get information on the climate over such an enormous time frame?
There's actually several ways, but the data we'll be looking at comes from cylinders of ice, cut out of a frozen lake in Antarctica that is more than two miles deep. The ice forms when successive years of snow pile on top, with the snow gradually becoming more and more compacted until it is frozen in place, locking in place whatever materials or gases were trapped when the layers formed.
Using a large body of chemical research about the composition of atmospheric gases and vapors at different temperatures, the ambient temperature when the ice was formed can be surmised.
The data set in question is linked here: VostokCoreData which came from research conducted by the World Data Center for Paleoclimatology in Boulder, and from the NOAA Paleoclimatology Program. Petit, J.R., et. al, 2001, Vostok Ice Core Data for 420,000 years, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-076.
Further background information on the data set can be found here (written by Laura)
The data is broken into subsets, and each member of the group will separately analyse one of the subsets. For each subset:
- What is the rate of temperature change?
- What is the timespan of the data?
- How much warming or cooling occurred in the subset?
As a group, answer the questions:
- What is the average rate of change when the climate is cooling?
- What is the average rate of change when the climate is warming?
- When is the maximum recorded temperature? When is the minimum?
- When is the highest rate of change of temperature?
- How do the long timescale rates of change compare to changes in the modern era?
- Given what you can see in this data set and what you know of climate change, what can you say is the best argument that can be made that modern climate change is not very important?
- What is the best argumant that can be made that modern climate change is very important?
Day 4
Quiz on significant digits, graph interpretation, and using slopes and rates to make predictions.
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