Chapter 18, pgs 523-534 (Chapter 18, pgs 452-461)

This is a text version of the notes presented in class.

Feel free to email the instructor (knamjesn@kent.edu) with any
comments about the format and ease of use of these online notes.

1.  Ocean and Climate:  Life in the Greenhouse
- Natural Climate Change
- What is the Greenhouse Effect?
- Climate Change and the Future

Graphic: Sunrise over the Beaufort Sea in the Arctic.   The potential impacts of
climate change may be felt early and very severely here.  Rear Adm. H.D. Nygren,
photographer. Courtesy of NOAA.
 

2.. Climate Forcing
External forcing:
    1)  From changes in Earth’s orbit
- due to changes in Earth's orbit about the sun
- occurs on time scales of 20,000-100,000 years

    2)  From changes in amount of heat emitted from Sun
 Occurs on time scales of decades to over a thousand years

3. Internal forcing:
    1)- due to variations of atmospheric and oceanic circulation
- occurs on time scales from tens to thousands of years
 (e.g., El Niño)

    -2) due to volcanic eruptions (cooling) or methane gas releases (warming)
these are not on a cycle, and have varying effects
 

4. Measuring Climate Change
Scientists can monitor past climate using natural climate recorders
Examples:
- chemical composition of coral skeletons
- air bubbles trapped in polar ice caps
Graphics: (above) Diver drills for coral samples, courtesy of NOAA,  (right) Reconstruction of
Rarotonga SST from coral.  Data from Linsley,  B., et al., Science (290) 1145-1148, 2000. World
Data Center for Paleoclimatology Data Contribution Series 2000-065.

5. Global Climate Connections
Over the past 60,000 years, similar climate variations have been recorded at widely separated areas
Thus many climate changes are "global"
Example: ice ages
Graphic: Reconstruction of organic carbon changes off Baja California from Ortiz et al., GSA 2000
and the GISP Ice Core d18O temperature record.

6. The Greenhouse Effect
"Greenhouse gases" in the  atmosphere trap heat, resulting in higher surface temperatures
Graphic: Garrison, Fig. 8.3, pg. 205 (pg. 180).

7. Life in the Greenhouse
The greenhouse effect is a natural part of how the atmosphere works
Natural sources of greenhouse gases:
- volcanic activity
- burning and decay of organic matter
- respiration and other biological processes
Graphic: Oldoinyo Lengai, erupts explosively in 1966.  Photography by G.Davies, courtesy of
C.Nyamweru, St. Lawrence University, Canton NY.

8.  9. A Planetary Comparison
Venus, Earth and Mars are all warmed to different degrees by greenhouse gasses in their atmospheres
Without the greenhouse effect average Earth surface temperatures would be -18^OC (0^OF)
Actual average surface temperatures were 16^OC (61^OF) prior to industrialization

9.  10. Anthropogenic Inputs of Greenhouse Gases
Carbon dioxide - fossil fuels, deforestation
Water vapor - changes in land use, ocean warming
Methane - rice farming, ranching
CFCs - cleaning agents, refrigerants
Graphic: Garrison, Fig. 18.21, pg 525 (Fig. 18.23, pg 454)

10. The Fossil Fuel Connection
Burning fossil fuels produces CO2 and water and releases heat
Example: burning 1 gallon of gasoline produce 19.6 lbs of CO2
 The impact of a population on atmospheric CO2 depends on:
  - size of population
  - affluence per capita
  - impact of affluence (i.e., technologies used)
Current CO2 emissions*:
 North America:  ~5 metric tons carbon per person per year
 Western Europe ~2 metric tons carbon per person per year
 Africa              ~0.3 metric tons carbon per person per year
*Data source: Carbon Dioxide Information Analysis Center, USDOE

11. Atmospheric CO2, 1950-1990's
Atmospheric CO2 can be measured directly from air samples
Measurements at Mauna Loa, Hawaii show an increase in atmospheric CO2 of 85 parts per million
(ppm) over the past 50 years
Data source: Keeling, D.C., and T.P. Whorf, 1998: Atmospheric CO2 records from sites in the SIO air
sampling network.  In "Trends: A Compendium of Data on Global Change", Carbon Dioxide Information Analysis
Center, US Dept. of Energy.

12. Atmospheric CO2, 1740-1990's
Air bubbles within polar and glacial ice are analyzed to determine CO2 levels in the past (yellow squares)
Atmospheric CO2 increased nearly exponentially from 280 ppm in the 1740's to about 370 ppm today
Other greenhouse gases have also increased
Graphic:  Garrison, Fig. 18.22, pg 526 (Fig. 18.24, pg 455).

13. Just How Unusual is the Present Level of CO2?
Data shows that today's CO2 levels were last reached  125,000 years ago
Some climatologists believe that a doubling of today's  CO2 level last occurred 20-40 million years ago
 

Next Lecture:  The Future of the Oceans
And REVIEW FOR FINAL EXAM