1. © 2008 W. H. Freeman and Company
WILLIAM F. RUDDIMAN
EARTH’S CLIMATE
PAST and FUTURE
SECOND EDITION
CHAPTER 10
Orbital-Scale Changes in Carbon Dioxide and Methane
© 2008 W. H. Freeman and Company

2. What was the main driver of tectonic timescale climate change?
Atmospheric CO2 levels
Did atmospheric CO2 levels change with the glacial/interglacial cycles?
YES!
How do we know they changed?
From measurements of air bubbles trapped in Antarctic ice
Record now goes back over 600,000 years

4. Courtesy of Paul Mayewski, University of Maine

5. Courtesy of Paul Mayewski, University of Maine

6. Courtesy of Paul Mayewski, University of Maine

10. Activity: What does this figure tell you?
When ice volume is low, CO2 levels are at their maximum ( ppmv) and visa versa (minimum ppmv)
CO2 seems to change roughly in tandem with changes in ice volume
What doesn’t this figure tell you?
How CO2 levels are related to changes in ice volume

11. Last full cycle showing error bars on measurements

12. Atmospheric CO2 and the Ice Ages
Activity: Why might these be linked?
Hint: what parts of the carbon cycle are affected by the ice ages?
Many possibilities:
CO2 more soluble in colder ocean
Oceanic biologic activity fertilized by glacial dust
Changes in ocean pH
Potential for positive feedback between CO2 and ice volume (p )
Problem not solved!

13. Tracer to look at changes in distribution of C in global carbon reservoirs = carbon isotopes

14. Which reservoir of C has the largest capacity to absorb extra C?

15. Evidence that
the strength of
Thermohaline
Circulation
has changed
with the glacial
cycles is clear
How exactly
this affects the
CO2 concentration
of the atmosphere
is not clear

16. What is the main source of
Methane in nature?
Given the insolation
the ice-core methane
record is compared to on
the right, which orbital
cycle is driving the change
in methane?
What climatic phenomenon
is driving the change
in methane?

17. What drives what? The
Paleoclimatologist’s
puzzle
According to the graph on
the right, which comes first,
changes in methane or
changes in ice volume?
Which came first, changes
in CO2 or ice volume?
Based on these relationships,
Ruddiman argues that CO2
and methane can play a role
in forcing ice volume changes
and as a feedback mechanism
for ice volume changes

18. precession
tilt