Greenhouse Effect and Global Warming

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 !!!

Energy Balance

Greenhouse Gases Carbon dioxide – CO 2 Methane – CH 4 Nitrous oxide – N 2 O Freons – CFCs (totally anthropogenic) What makes it a GHG??? Water vapor – H 2 O

GHG Concentration Changes Years

Global Warming An increase in global temperatures due to increases in the concentrations of greenhouse gases Increased CO 2 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 CO 2 –Fewer trees, less photosynthesis Fertilizers CFCs Methane

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 A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September See Atmospheric carbon dioxide (CO 2 ) concentrations (1750 to present)

Data Source: Marland et al, Carbon Dioxide Information Analysis Center. Cumulative carbon emissions,

Variations in the Earth’s surface temperature

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

Reducing GH Emissions

Solutions

Global Agreements IPCC – Intergovernmental Panel on Climate Change  1988 UNEP Rio de Janeiro  1992 Kyoto Protocol  1997 –Ratified Nov – U.S. and Australia have not signed the treaty

U.S. Position Bush Sr. (1988 – 1992) Clinton (1992 – 2000) Bush Jr. (2000 – 2008) Obama ( )