Page 119 - Earth's Climate Past and Future

CHAPTER 5 • Greenhouse Climate 95

chemical weathering and burial of the excess carbon in 4. What are the possible causes of mismatches
ocean sediments. between the models and geologic observations?
This episode is potentially important to our future
because it is at least a partial parallel analog to the 5. Why do some climate scientists believe that
increased ocean heat transport is required to
changes humans are now producing by our industrial explain polar warmth 100 Myr ago?
releases of carbon into the climate system. The thermal
maximum 55 Myr ago is estimated to have required the 6. Which regions of the continents were flooded by
addition of several tens of trillions of carbon to the high seas 100 Myr ago?
atmosphere. In comparison, during the last two centuries 7. What were the major factors that explain higher
since the start of the Industrial Revolution, humans have sea level 100 Myr ago?
added several hundred billion tons of carbon to the
atmosphere. According to conservative extrapolations of 8. How did higher sea levels affect global climate?
recent trends, we will add several thousand more billions 9. Do sea level changes explain past glaciations?
of tons of carbon to the atmosphere in the next 200 to
300 years. We face a smaller future warming than that 55 10. Did asteroid impacts have long-lasting effects on
Myr ago, but it will arrive within a few hundred years climate?
rather than over 10,000 years.
Additional Resources
Key Terms
Basic Reading
Cretaceous (p. 82) regressions (p. 86) Companion Web site at www.whfreeman.com/
ocean heat transport eustatic sea level (p. 87) ruddiman2e, pp. 9–11, 13–15, 32, 34–35.
hypothesis (p. 85) thermal expansion Alvarez, L. W., W. Alvarez, F. Asaro, and H. V. Michel.
warm, saline bottom coefficient (p. 90) 1980. “Extraterrestrial Cause for the Cretaceous-
water (p. 85) hypsometric curve Tertiary Extinction.” Science 208: 1095–1108.
CO saturation (p. 86) (p. 91)
2
transgressions (p. 86) methane clathrate (p. 94) Advanced Reading
Barron, E. J., S. L. Thompson, and S. H. Schneider.
1981. “An Ice-Free Cretaceous? Results from a
Review Questions Model Simulation.” Science 212: 501–8.
Miller, K., et al. 2005. “The Phanerozoic Record
1. What evidence shows that the world was warmer of Global Sea-Level Change.” Science 312:
100 Myr ago than today? 1293–98.
Oglesby, R. J., and B. Saltzman. 1992. “Equilibrium
2. Why do higher CO levels make sense as an
2 Climate Statistics of a General Circulation Model as
explanation for this greater warmth?
a Function of Atmospheric Carbon Dioxide.” Part I:
3. How well do model simulations capture the “Geographic Distribution of Primary Variables.”
distribution of temperatures 100 Myr ago? Journal of Climate 5: 66–92.