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

\