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MET 112 Global Climate Change – Lecture 11
Observations ofRecent Climate Change
Dr. Craig ClementsSan 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)
•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 summer
•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.
What Changed Around 1800?
Industrial Revolution– Increased burning of fossil fuels
Also, extensive changes in land use began– the clearing and removal of forests
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)
Anthropogenic Methane Sources
Leakage from natural gas pipelines and coal mines
Emissions from cattle Emissions from rice paddies
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
HW Due: Tues November 13 From the article on CO2 sinks (Canadell et al. 2007) given
last week…summarize the article. (1 paragraph only)
and
Pick ONE reference used in the article and find it either through the library or online. Download the article and read it.
Write 1 paragraph on how that reference was used in the Canadell et al. 2007. Include the entire downloaded article (HARD COPY) as an attachment.
No emailed assignments will be accepted.