Part IV: Historical Climate Changes
Lecture 18: The Little Ice Age
(Chapter 15)
Frequency of sea ice intrusion along the coast of Iceland
MW: 1000-1300
Vikings invaded
southwestern Greenland
LIA: 1400-1900
Vikings abandoned
Greenland
Canada arctic lichen
Dead lichen
due to snow
expansion
indicates the
time of LIA
Mountain glacier:
Annual layer,
δ18O,
Dust content,
MW
Ice core in Peruvian Andes
LIA
Ice cores in
four regions
Temperature change, not uniform!
Warming?
MW and LIA seems to be present
in tropical mountain glaciers, but
not obvious in Greenland and
Antarctic ice sheets
Global?
MW
LIA
Tasmanian tree rings
MW? LIA? Not obvious
in SH
Unprecedented
warming?
Reconstructed NH temperature
(hockey stick pattern)
Global
warming?
MW?
LIA?
Longest Instrument record
LIA? Global warming?
Temperature stations,
Urban heat island effect
Global surface temperature
1910
Recession of
the Grinnell
Glacier
“Glacier
National Park”
1997
Source: D. Fagre, USGS, 2004
15
Kilimanjaro ice extent (km2)
10
5
?
0
1900
1920
1940
1960
Year
1980
2000
2020
Little Penck Glacier, Kilimanjaro
Sea level rise
5cm upper ocean warming, 3 cm land ice melting, 2 cm Greenland ice melting
Increased cloud cover
Unclear warming or cooling effect because
unknown high or low clouds
Arctic sea ice
Arctic clouds
(warming or cooling?)
The growing season lengthens in Alaska
Tree Ring Width
Obs.
Trend
Tree ring
Obs.
Tair
Model
P~R
Global Greening Trend
(FPAR: Fraction of Photosynthetically Active Radiation)
Total CO2
Physiology
Carbon fertilization
Radiation
Obs. >1980
Obs. – crops
Decrease in snow cover
Reduced Arctic sea ice cover
and thickness !
Global Lake Open/Close Date
Lake
Mendota
Fundamental Questions on MW/LIA
1) Are these change regional or global?
2) Is it cause by orbital forcing of
reduced summer insolation or
millennial variability?
3) What caused the rapid warming
since 1900 that terminates the LIA?
Forcing mechanism
for centennial and decadal variability
• Solar forcing
• Natural variability: PDO, NAO
11 year cycle: solar radiation and sunspots
More Sunspots
More solar radiation from
faculae
Sunspot history from
telescopes
Forcing mechanism
for interannual variability
• Volcanic forcing
• Natural variability: ESNO
Relation between ENSO and volcanic activity?
Eruption of Mount Pinatobo in
1991 and global cooling
(Tropical) Volcanic cooling
End of Lecture 19
Lecture 20: El Nino, La Nina and
Southern Oscillation
(Chapter 16)
Change of Climate Variability
Tropical Pacific SST
El Nino and Southern Oscillation: ENSO
http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html#figure
Historical record of El Nino
Corals and tropical ocean
Annual layers made of CaCO3,
take ocean water δ18O (a proxy of
temperature, but also with
salinity effect)
LIA?
El Nino
Evolution of the last 21,000 yrs
Deglaciation, but not smooth
Change of Climate Variability
Tropical Pacific SST
1935 Texas (Dustbowl)
1997 Kansas
Global surface temperature
North Africa Climate Change
SAHEL RAINFALL
SST decadal variability!
S. Nicholson
Charney
Charney
Climate Change: Global to Regional Perspective
Global
Wisconsin
US
Madison
End of Lecture 20
Tibet ice core
Tree-ring
(dendroclimatology)
Arctic tree ring
Asian tree ring
Strong centennial
/decadal variability
Natural Climate Variability