Atmospheric Sciences 211

Midterm exam 2

Tuesday, February 21, 2001



(1) Explain why winters in northern Europe are relatively mild, compared to
      locations at similar latitudes in Canada and the northern United States.
      (10 points)

(2) Explain how the biological pump in the oceans works.  How does it affect the
      concentration of carbon dissolved in sea water at the ocean surface?  How does it
      influence how limestone sediments on the sea floor are distributed with respect to
      the depth of the ocean? (15 points)

(3) Describe the role of weathering in the carbonate-silicate cycle.  What kind of
      chemical transformation is involved?  What happens to the products of the
      reaction? (10 points)

(4) Why do the atmospheres of Jupiter and Saturn contain so much more hydrogen
      (mostly in compounds like methane and ammonia) than the Earth's atmosphere?
      (10 points)

(5) How do we know that the climate of North Africa was more moist 2,000 years ago
      than it is today? (10 points)

(6) Compare and contrast the Younger Dryas event, which occurred slightly more
      10,000 years ago and the last major ice age, which was at its peak 20,000 years
      ago. (10 points)

(7) Why aren't scientists concerned about the possibility that the burning of
      fossil fuels could seriously lower atmospheric oxygen levels? (10 points)

(8) For each of the following kinds of proxy evidence, indicate the time scale on
      which it provides useful information on past climate variability.  (a) tree rings,
      (b) 'redbeds' containing ferrous oxide (c) ice cores (d) magnetic stripes, (e)
      fossils.  In answering the question use the categories A lifetime of the earth, B
      the past 100 million years, C the past million years, D the past 20,000 years, and
      E the past 2000 years.  Note that some kinds of proxy evidence provide useful
      information on more than one time scale.

(9) In terms of the orbital theory of the ice ages, are present conditions more or
     less favorable for the growth of continental ice sheets in the Northern Hemisphere
     than conditions of 10,000 years ago or 10,000 years in the future?  Explain your
     answer.  (Hint: focus on the distance between the earth and the sun at various
     points in its orbit). (10 points)

(10) Why do scientists ignore continental drift and orbital cycles in making
        predictions of climate change during the 21st century?  (5 points)