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.

Temperature stations

Change in surface temperature in 20th 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: 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.

Ice Cores

Coring Earth’s ice sheets

Coring mountain glaciers

Ice core record

Ice core CO2 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 20th century

Shorter winters in Alaska

Latest global temperatures

Current CO2: ~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 N2O

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

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.