March 16

Lecture Outline - March 16

The Science of Climate Change    

 I.    Two Types of Scientific Errors

• Type I:    to conclude that there is a significant human imprint on the global climate when there is none

• Type II:    to fail to detect a significant human imprint on the global climate when one actually exists

II.    Knowledge of Climate Change

                    Role of Intergovernmental Panel on Climate Change                         Climate Arc website

• The Theory of the Greenhouse Effect

                  diagram of the greenhouse effect

                  comparisons of the atmospheres of Venus, Earth and Mars

                  CO2 Monitoring Records   (increase in 2004 up to 3 ppm, compared to 1.8 annual average over last decade)

                  cooling factors

• Paleoclimatological Research

                 temperature and CO2  concentrations over past 400,000 years

III.    Recent Anomalies in Global Average Mean Temperature

                    Trends in global annual mean temperatures

"In light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations,"  IPCC 2001 Report.

• •         -1998 - the warmest single year since 1860;  followed by 2002, 2003, and 2004  (2005 on track to be 1st or 2nd warmest)

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  •                       Global average temperatures tend to be higher during El Nino cycles   (map of Pacific Ocean)

  •         -10  warmest years  since 1860 occurred since1990; all of 1990s years were among among top 15 

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  •         -for 23 consecutive years the average temperature has been above the 1960-1990 annual average 

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  •         -16 consecutive months in 1997-98 broke temperature records 

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  •         -increase of 0.5 degrees Celsius since 1975 (based on five year mean temperatures) -- 

  •                     or a rate of 2 degrees Celsius per century

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IV.    Possible Harbingers of Global Climate Change

• • -a decrease of approximately 10% in the extent of snow cover since the late 1960   

  • -a 14% reduction in the amount of perennial Arctic Sea ice between 1978-1998 and a 40% reduction in ice thickness over the last 20-40 years  

    • -an increase of .31 C in the temperatures of the top 300 meters of the Atlantic, Pacific, and Indian Oceans over the past 50 years  

    • -an advance of 9.8 days in freshwater spring thaw dates at 38 sites in the northern hemisphere sites between 1846 and 1996, and an 8.7 day delay in fall freeze-up dates 

    • -a rise in average winter termperatures as much as 7 degrees F in Alaska, Western Canada, and eastern Russia

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    • -a shrinking of of  212 of 242 Antarctic glaciers by an average of 600 meters over last 50 years  (also rapid melting of Arctic glaciers)

    • -a retreat of mountain glaciers in non-polar regions during the 20 century  

    • -an increase of 2-4% in the frequency of heavy precipitations events during the latter half of the 20th century  

    • -a rise in sea levels of .1 to .2 meters during the 20th century 

    • -a substantial drop in the amount of long-wave radiation escaping from the earth between 1970 and 1997 

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V.     Projections of Future Climate Change (global average mean temperatures)

           (from reports of the IPCC)

• 1995 Report

  •     1.8 to 6.3°F

• 2001 Report

  •     2.5  to 10.4°F (upward estimate to lower anticipated levels of SO²)