Lecture 12: Climate Change and Life in the Greenhouse
New Version - Updated by dwitter, 26 Feb 2007

1. Climate Change - Life in the Greenhouse
- Natural Climate Change
- What is the Greenhouse Effect?
- Climate Change and the Future
Reading:  4th Ed., Ch 18, Sec 21 or 5th Ed., Ch 18, Sec 22
Graphic: Garrison, 4th Ed., Fig. 18.22, pg 483, 5th Ed., Fig. 18.26, pg 455.

2. What Causes Climate?
Many changes in climate are driven by energy from the sun
Climate depends on:
- the amount of energy received
- what happens to this energy once it reaches Earth's atmosphere
Graphic: Earth's orbit, adapted from Pisias and Imbrie (1986/1987). Courtesy of NOAA Paleoclimatology Program, T.G. Andrews.  http://www.ncdc.noaa.gov/paleo/slides/slideset/11/11_183_slide.html

3. Climate Forcing
External forcing:
- due to changes in Earth’s orbit about the sun
- occurs on time scales of 20,000-100,000 years
Internal forcing:
- due to variations of atmospheric and oceanic circulation
- occurs on time scales from tens to thousands of years
Graphics: (top panels) Changes in orbit circularity ("eccentricity"), images by R.Simmon, courtesy of NASA GSFC. (bottom) Sea level signatures of El Niño and La Niña measured by the TOPEX/-POSEIDON satellite altimeter. Image courtesy of NASA JPL.

4. Heat Exchange and Climate
Solar energy is unevenly distributed:
- excess heat in the tropics
- deficit of heat at the poles
Different climates can be produced with the same amount of solar energy as energy is redistributed by oceanic and atmospheric circulation
Graphics: Garrison, 4th Ed., Fig. 8.4, pg 189, 5th Ed., Fig. 8.5, pg 181.

5. 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) Banding in coral skeletons NOAA Coral Paleoclimate slide set.

6. The Greenhouse Effect
"Greenhouse gases" in the atmosphere trap heat, resulting in higher surface temperatures
Graphic: See Garrison, 4th Ed., Fig. 8.2, pg 188, 5th Ed., Fig. 8.3, pg 180.

7. Life in the Greenhouse
The greenhouse effect is a natural part of how the atmosphere works
Natural sources of greenhouse gases:
- volcanoes
- 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. A Planetary Comparison
Venus, Earth and Mars are all warmed by greenhouse gases in their atmospheres
Without the greenhouse effect average Earth surface temperatures would be -18 degC (0 degF)
Actual average surface temperatures were 16 degC (61 degF) prior to industrialization

9. 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, 4th Ed., Fig. 18.19, pg 482, 5th Ed., Fig. 18.23, pg 454.

10. Indicators of the human influence on the atmosphere during the industrial era
Graphic: http://www.ipcc.ch/present/graphics/2001syr/large/02.01.jpg

11. 400 Thousand Years of Atmospheric Carbon Dioxide Concentration and Temperature Change
Graphic:  http://www.whrc.org/resources/online_publications/warming_earth/scientific_evidence.htm see Fig. 1

12. Potential Climate Changes
Primary effects:
- Warmer temperatures
- Higher sea level
- Reduced seasonal snowpack
- Retreating glaciers
- Reduced permafrost
- More intense, longer droughts
- Increase in intense tropical cyclones (hurricanes and typhoons)
Types of changes:
- changes in average conditions
- changes in variability
- rapid changes
- "surprises"
Graphic: (top) Hurricane Floyd, Sept. 14, 1999. Courtesy of NASA, (bottom) TOPEX/Poseidon satellite sea level observations, courtesy Arctic Climate Impact Assessment, 2004. http://www.amap.no/acia/Files/ObsGlobalSeaLvlRise_150.jpg

13. Variations of Earth's Surface Temperature (past 140 yrs - global , past 1000 yrs - northern hemisphere)
Graphic: http://www.ipcc.ch/present/graphics/2001syr/large/05.16.jpg

14. Scientific Predictions of Future Warming
Graphic: Projected surface temperature changes for early and late 21st century relative to 1999. Scenarios: (top) B1-shift to sustainable fuels, population peaks mid-century, (middle) A1B-rapid future economic growth, fossil and non-fossil fuels, (bottom) A2-fossil fuel intensive, regional responses with increasing global population. Fig. SPM-6, IPCC Working Group 1 Executive Summary, 2007.
Graphic: http://www.ipcc.ch/SPM2feb07.pdf Fig. SPM-6, pg 15.

15. What causes sea level to change?
Graphic: http://www.ipcc.ch/present/graphics/2001syr/large/04.02.jpg

16. Global average sea level rise (1990-2100) for the six SRES scenarios
Graphic: http://www.ipcc.ch/present/graphics/2001wg1/large/04.03.jpg

17. Global Impacts of Sea Level Rise
- Damage to housing and high-value infrastructure
- Altered patterns of damage by storm waves
- Potential refugee issues involving low-lying coastal nations
Graphics: (left) Impact of a 1 meter rise in sea level on Florida. In relatively flat coastal areas, a small rise in sea level can flood large areas (right). Graphics from “Impacts of a Warming Arctic: Arctic Climate Impact Assessment", Cambridge University Press, 2004. http://www.amap.no/acia/Files/ObsSeaIceNASA1979_03_150.jpg  http://www.amap.no/acia/Files/SeaLvlRise-Coastline_150.jpg

18. What About the Melting of Ice on Greenland?
Graphics: (left) Meltwater flowing into a moulin, courtesy R.J. Braithwaite, University of Manchester, UK, (top right) seasonal meltwater zone around Greenland, as measured by satellite. Courtesy of “Impacts of a Warming Arctic: Arctic Climate Impact Assessment”, Cambridge University Press, 2004, (bottom right) glacial melt processes, NASA GSFC.
See http://www.gsfc.nasa.gov/gsfc/earth/pictures/20020606greenland/figure1m.jpg and http://www.gsfc.nasa.gov/gsfc/earth/pictures/20020606greenland/iceflow.jpg and http://www.amap.no/acia/Files/GISMeltExt_150.jpg

19. Sea Ice Trends
Sea ice:
- cools climate by reflecting solar energy back to space
- is an important habitat for many marine animals
- is decreasing by 2.7% per decade, with largest decreases (7.4% per decade) in summer
Analyses indicate a seasonally ice-free Arctic by 2050
Graphic: (top) Sea ice coverage, 1979 and 2003 based on satellite data, courtesy of “Impacts of a Warming Arctic: Arctic Climate Impact Assessment”, Cambridge University Press, 2004, (inset) Sea ice trends as measured by satellite, courtesy of National Snow and Ice Data Center.  http://www.amap.no/acia/Files/ObsSeaIceNASA1979_03_150.jpg and http://www.amap.no/acia/Files/ObsSeaIceExt1900-03_150.jpg

20. Ocean Acidity (pH) and the Future
- Shell-building organisms form an important part of many marine food webs – many of these can survive in only a narrow range of pH
- Compared to pre-industrial levels, the pH of the surface ocean has fallen by 0.1 units. As the ocean continues to absorb CO2, pH may fall by an additional 0.14-0.35 units by 2100*
- Potential impacts: Lower pH makes it difficult for marine organisms to build calcium carbonate shells and skeletons, potentially impacting marine food webs
Photos: (top) Micrograph of a coccolithophore, courtesy of NASA, (bottom) Red Sea coral reef, courtesy of NOAA,
* = From Climate Change 2007: The Physical Science Basis, IPCC Working Group I, Summary for Policymakers, 2007.

21. Potential Impacts on Coral Reefs
Graphic: Impacts of Ocean Acidification on Coral Reefs and Other Calcifiers, Workshop Report (NSF, NASA, USGS), see http://www.ucar.edu/communications/Final_acidification.pdf, pg 10.

22. Potential Impacts of Climate Change on Society
Many sectors of society may be affected...
- Agriculture and fisheries
- Infrastructure
- Water resource management
- Human health
- Ecosystems/biodiversity
Climatologists, economists, sociologists, politicians and others are studying the potential impacts of climate change on these sectors and on individual countries
Graphic: (top) Sunrise, courtesy of NOAA, (bottom) wheat harvest, at ARS Central Great Plains Research Station, Akron, Colorado. Photo by S.Bauer, courtesy of US Dept. of Agriculture.

23. Predicting Future Climate
Uncertainties:
- Interactions between different elements of the climate system (e.g., global warming and clouds)
- Future CO2 emissions are unknown
- Potential impacts of mitigation technologies
- Unforeseen surprises
Graphic: Climate change feedbacks, courtesy of United Nations Environmental Program, World Meteorology Office.

24. What Does the Future Hold?
Options being studied and pursued include:
Mitigation to reduce emissions:
- using fewer fossil fuels
- energy efficiency
- substitution of technologies
- removing CO2 once it's produced ("sequestration")
Adaptation to a new climate
- may require sweeping changes in key sectors of society (e.g., farming, insurance)
- success depends on available capital and other resources
Graphics: (top left) Engine from a Toyota Prius, photo courtesy of Oak Ridge National lab, (top right) Cool change logo, courtesy of USEPA, (center) Toyota Prius, photo courtesy of NPS, (bottom) wind farm, photo courtesy of US DOE.

25. Preview of Next Lecture
Tsunami
Review for Exam 2
Reading: 4th Ed., Ch 11 Secs 5-10 or 5th Ed., Ch 10 Secs 24-29
Graphic: Fishing boat beached near a damaged fire truck. Photo by D.J. Sigrist International Tsunami Info. Center, Honolulu. Courtesy of NOAA.