Climate Change in the Geological Record

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Climate Change in the Geological Record

• David Lea, Department of Earth Science,
  University of California, Santa Barbara

Coast Geological Society, April 21, 2009
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NOAA ESRL The graph shows a record of mean
carbon dioxide measured at Mauna Loa Observatory,
Hawaii (http//www.esrl.noaa.gov/gmd/ccgg/trends/)
. Updated4/09.
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NOAA ESRL Radiative forcing of all the
long-lived greenhouse gases, relative to 1750,
and the NOAA Annual Greenhouse Gas Index (AGGI)
on the right axis, which is indexed to 1 on
January 1, 1990 (http//www.esrl.noaa.gov/gmd/aggi
/). Kyoto target is 5 below 1990 levels.
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NASA GISS Global annual surface temperature
anomalies (C) relative to 1951-1980 mean based
on surface air measurements at meteorological
stations and ship and satellite measurements for
sea surface temperature. Green error bars
indicate uncertainty (http//data.giss.nasa.gov/gi
stemp/)
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Paleoclimate - the study of past climate change

• How do todays greenhouse gas levels compare to
  atmospheric levels in the geological past?
• What is the relationship between past greenhouse
  gas levels and climate?
• Can we predict future climate change, such as
  temperature or sea level, using those past
  relationships?
• Can we compare the present climate to the past to
  determine what constitutes a dangerous level of
  climate interference?

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Living foraminifera Globigerinoides ruber
Shell preserved in marine sediment
Shell produced by living foram
0.25 mm
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Cariaco Basin Laminated Sediment
Younger Dryas time interval 11,900 - 12, 150 yrs
BP
Depth in cm
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Core MD98-2162, 32.5 to 33 m core depth, 125,000
yrs BP.
volcanic ash rich sample!
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Cocos Ridge
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Tropical temperatures
Antarctic temperatures
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19045 - 19292 yr BP
Dyke et al., 2003
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Cocos Ridge SST vs. Vostok CO2
Lea, 2004, JCLI
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Tropical temperature change versus greenhouse
forcing
2009
Predicts a 4.4 - 5.6C increase for doubling
of CO2
IPCC AR4 models
Lea, 2004, JCLI
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Tropical Pacific SST Core Sites
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Makassar Straits 117.9E, 4.69S, 1855m water
depth
()
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Makassar Straits SST vs. Dome Fuji, Antarctic
air-T
r2 0.84
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Makassar Straits SST vs. Dome Fuji CO2
r2 0.80
3 Wm-2
(ppm)
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One hypothesis to link CO2 with Southern Ocean
and tropical warming (Toggweiler et al., 2006)
Newest Idea Milankovitch (orbital variations)
drove shifts in SH westerlies via the influence
of seasonal insolation on ITCZ position.