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Greenhouse Effect and Global Warming. Greenhouse Effect. Key Factors Earth-Sun Temperature Differences Greenhouse Gas Concentrations
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Greenhouse Effect • Key Factors Earth-Sun Temperature Differences Greenhouse Gas Concentrations • The atmosphere is transparent to incoming solar radiation (short wave, high energy), outgoing terrestrial radiation (longer waves, lower energy) is absorbed by GHGs. (also relates to Black body radiation) →WIEN’S LAW !!!
Greenhouse Gases • Carbon dioxide – CO2 • Methane – CH4 • Nitrous oxide – N2O • Freons – CFCs (totally anthropogenic) What makes it a GHG??? • Water vapor – H2O
Global Warming • An increase in global temperatures due to increases in the concentrations of greenhouse gases • Increased CO2 concentrations exerts largest radiative forcing (i.e., explains bulk of temperature increase) • NOT CAUSED BY STRATOSPHERIC OZONE DEPLETION
GHG Sources • Combustion of fossil fuels • Deforestation (loss of sink) • Slash and burn techniques release CO2 • Fewer trees, less photosynthesis • Fertilizers • CFCs • Methane
Atmospheric carbon dioxide (CO2) concentrations (1750 to present) Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm
Cumulative carbon emissions, 1950-1996 Data Source: Marland et al, 1999. Carbon Dioxide Information Analysis Center.
Impacts • Rise in sea level • Thermal expansion of the oceans • Melting ice caps and glaciers • Climatic shifts • Shifts in agriculture • Increase in disease • Declines in biodiversity • Coral bleaching
Global Agreements • IPCC – Intergovernmental Panel on Climate Change 1988 UNEP • Rio de Janeiro 1992 • Kyoto Protocol 1997 • Ratified Nov. 2006 • U.S. and Australia have not signed the treaty
U.S. Position Bush Sr. (1988 – 1992) Clinton (1992 – 2000) Bush Jr. (2000 – 2008) Obama (2008 - )