E

AP Environmental Science 9.4-9.5: Greenhouse Gases and Global Climate Change

Main Questions:

  • Is it proven?
  • What are potential consequences?
  • What can be done?

How Does This Relate to the Carbon Cycle?

  • Sources of Increased Atmospheric CO2
    • Burning Fossil Fuels
    • Deforestation
  • Carbon Balance: increased atmospheric CO2 less than expected based only on input
    • about 49% remains in atmosphere
    • about 29% uptake by oceans
    • carbon balance:  about 22% unaccounted for

Consequences of Increased Greenhouse Gases

  • Human activity and natural processes lead to…
  • Increased atmospheric greenhouse gases, which leads to…
  • An increase in average global temperature, which causes…
  • Changes in climate, which can lead to…
    • Droughts
    • Increased rainfall and storms
    • Rising sea levels
    • Loss of biodiversity

Climate Changes During the Past 900,000 Years

  • Past cimate based on study of Antartic glaciers

  • Cycles of Ice Ages lasting about 100,000 years

  • Interglacial Periods lasting 10,000 to 12,500 years

Climate During the Past 160,000 Years

  • End of last Ice Age about 10,000 yr BP

  • ==Now in warm interglacial period==

  • Based on ice core data, analysis of trapped gas

  • Correlation between CO2 and mean temperature

What is the Scientific Consensus?

  • Mean global temperature rose about 0.6º C (1º F) in past 100 years
  • ==Increase is real,== not explained by natural variation in solar radiation
  • Warming greater at poles than equator, greater at night, ==mostly troposphere==

Future Scenarios

  • ==General Circulation Models (GCMs)== are used to predict future climates
  • Projected warming of 1 to 3.5 º C between 1990 & 2100
  • Likely scenario: doubling of CO2 (from 280 ppm to 560 ppm) before 2100 leading to warming of 2ºC

Role of the Oceans

  • Storage of CO2 in deep water

  • ==Warming could decrease ability of ocean to serve as “sink” for carbon==

Ecological Implications

  • Shift of habitat to higher latitudes
  • Shift of habitat to higher elevations
  • Potential large loss of biodiversity

Solutions to Global Warming

Prevention

  • Cut fossil fuel use (especially coal) in half
  • Improve energy efficiency
  • Shift to renewable energy resources
  • Reduce deforestation
  • Use sustainable agriculture
  • Slow population growth

Clean Energy Use

Cleanup

  • Remove CO2 from vehicular and smokestack emissions
  • Plant and tend to trees

Actions

  • Waste less water
  • Develop crops that need less water
  • Move hazardous materials storage tanks away from coast
  • Prohibit new construction or remodeling on low-lying coastal areas
  • Stockpile 1-5 year supply of key foods
  • Expand existing wildlife reserves toward the poles
  • Connect wildlife reserves with corridors

International Agreements

Kyoto Agreement (1997)

  • 38 developed countries must cut greenhouse gas emissions to ==5.2% below== 1990 levels between 2008-2012
  • ==Developing countries exempted==
  • Allow emissions trading, in which countries can sell its excess reductions to others
    • Countries can also plant trees to meet goal
  • Impact on U.S.: Economic Incentives/Regulatory Changes
    • Reduce energy use by 18%
    • Reduce electricity use by 30%
    • Cut SO2 emissions by 50%
    • Cut NO2 emissions by 25%
    • ==Cut CO2 emissions by 14% below 1990 levels==
    • Twice the amount specified in the Kyoto Treaty