Post on 21-Dec-2015
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 LIA: 1400-1900
Vikings invaded southwestern Greenland
Vikings abandoned Greenland
Canada arctic lichen
Dead lichen due to snow expansion indicates the time of LIA
Mountain glacier:
Annual layer,
δ18O,
Dust content,
Ice core in Peruvian Andes
MW LIA
Ice cores in
four regions
MWLIA
Warming?
Global?
Temperature change, not uniform!
MW and LIA seems to be present in tropical mountain glaciers, but not obvious in Greenland and Antarctic ice sheets
Tasmanian tree rings
MW? LIA? Not obvious in SH
Unprecedented warming?
Reconstructed NH temperature (hockey stick pattern)
MW? LIA?
Global warming?
Longest Instrument record
LIA? Global warming?
Temperature stations,
Urban heat island effect
Global surface temperature
Source: D. Fagre, USGS, 2004
Recession of the Grinnell Glacier
“Glacier National Park”
1910
1997
Ice on Kilimanjaro
0
5
10
15
1900 1920 1940 1960 1980 2000 2020
Year
Kilimanjaro ice extent (km2)
?
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 WidthTree Ring Width
Obs. Trend
Tree ring
Tair
Model
Obs.
P ~ R
Global Greening TrendGlobal Greening Trend
Total CO2
Physiology
Carbon fertilization
Radiation
Obs. >1980
Obs. – crops
(FPAR: Fraction of Photosynthetically Active Radiation)(FPAR: Fraction of Photosynthetically Active Radiation)
Decrease in snow cover
Reduced Arctic sea ice cover
and thickness !
Global Lake Open/Close Date
Lake
Mendota
2) Is it cause by orbital forcing of reduced summer insolation or millennial variability?
Fundamental Questions on MW/LIA
1) Are these change regional or global?
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 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 Change of Climate Variability Tropical Pacific SST
1935 Texas (Dustbowl)1935 Texas (Dustbowl)
1997 Kansas1997 Kansas
Global surface temperature
SAHEL RAINFALL
North Africa Climate ChangeNorth Africa Climate Change
S. NicholsonCharney Charney
?
SST decadal variability!
Global US
Wisconsin Madison
Climate Change: Global to Regional PerspectiveClimate Change: Global to Regional Perspective
End of Lecture 20
Tibet ice core
Tree-ring
(dendroclimatology)
Arctic tree ring
Asian tree ring
Strong centennial /decadal variability
Natural Climate Variability Natural Climate Variability