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 Where do our observations come from? - to watch and record.

Temperature stations

Change in surface temperature in 20 th century

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:

Ice Core layers GISP2 ice core (Greenland Summit)GISP2ice core Archived at the National Ice Core Laboratory in CO. from 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

Ice Cores

Coring Earth’s ice sheets

Coring mountain glaciers

Ice core record

Ice core CO 2 record

Retreat of mountain glaciers: ‘visual inspection’ Boulder Glacier, Mt. Baker, Washington

Retreat of mountain glaciers

Melting of Greenland Icesheet

Global rise in sea level last 20,000 years

Global rise in sea level in the 20 th century

Shorter winters in Alaska

Latest global temperatures

Current CO 2 : ~383 ppm

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)

Greenhouse Gases  Carbon Dioxide  Methane  Nitrous Oxide  CFCs (Chlorofluorocarbons)  Others

Methane

Anthropogenic Methane Sources  Leakage from natural gas pipelines and coal mines  Emissions from cattle  Emissions from rice paddies

Nitrous Oxide N 2 O

Anthropogenic Sources of Nitrous Oxide  Agriculture  Bacteria in Soils  Nitrogen fertilizers

CFCs (Chlorofluorocarbons) CFC-11 CFC-12

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

Latest global temperatures

The Land and Oceans have both warmed

Precipitation patterns have changed