MET 112 Global Climate Change – Lecture 10 Observations of Recent Climate Change Dr. Craig Clements San Jose State University Outline How do we observe?
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MET 112 Global Climate Change – Lecture 10 Observations of Recent Climate Change Dr. Craig Clements San Jose State University Outline How do we observe? Recent trends in temperature Recent trends in GHGs
What does to observe mean? Measurements –Of what? Who compiles these measurements for governments and society? IPCC: Intergovernmental Panel on Climate Change www.ipcc.ch Where do our observations come from? - to watch and record.
Bubbles Trapped in ice core Petit, Jean-Robert, et al (1999). “Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica”. Nature 399: 429-436.
Ice Core layers GISP2 ice core (Greenland Summit)GISP2ice core Archived at the National Ice Core Laboratory in CO. from 1837-1838 meters in which annual layers are clearly visible. The appearance of layers results from differences in the size of snow crystals deposited in winter versus summerwintersummer Counting such layers has been used (in combination with other techniques) to reliably determine the age of the ice. This ice was formed ~16250 years ago during the final stages of the last ice age and approximately 38 years are represented here.ice age
Burning of Fossil Fuels Fossil Fuels: Fuels obtained from the earth are part of the buried organic carbon “reservoir” –Examples: Coal, petroleum products, natural gas The burning of fossil fuels is essentially –A large acceleration of the oxidation of buried organic carbon
Land-Use Changes Deforestation: –The intentional clearing of forests for farmland and habitation This process is essentially an acceleration of one part of the short-term carbon cycle: –the decay of dead vegetation Also causes change in surface albedo (generally cooling)
Sources of CFCs Leakage from old air conditioners and refrigerators Production of CFCs was banned in 1987 because of stratospheric ozone destruction –CFC concentrations appear to now be decreasing –There are no natural sources of CFCs