Transcript Weather - University of Arizona

This Class: Short-term climate change
• Climate – 30 year “average” weather
conditions
• Short-term – over the last 1000 to
12,000 years
• Climate records
• Causes of climatic variation
• Past climate change
Records of climate
Records of climate
• Historical (human) records
– instrumental
– written observations
• maritime records
– paintings
• 12,000 paintings
• 1400-1967
Records of climate, cont.
• Phenological observations
– agricultural records
• price of rye in Germany
– bird migrations
Dendrochronology
• dating of past events through study of tree
ring growth
• thickness of the tree ring indicates growing
season conditions
– precipitation
building a chronology
• overlapping rings from different trees
• Bristlecone pine chronology is 9000 years
long
– long lives - 4,767 years old
Lake and ocean sediments
• Sediments record
environmental
conditions present
when they were
deposited
Clues in the sediments
• pollen - vegetation type
• skeletons of small
organisms - water
chemistry, temperature
• type of organisms windiness
• chemistry of sediments or
organisms – temperature,
precipitation
Elk Lake, Minnesota
• http://geology.cr.usgs.gov/pub/factsheets/fs-0059-99/
Signals in Elk Lake sediments
• diatoms - heavy, need wind to keep
afloat = windy
• quartz - blown into the lake = windy
• sodium – retained in soils, not washed
away = dry
• pollen - vegetation type
• 8,500 to 4000 years ago it was drier,
prairie vegetation
Coral reefs
• growth bands
• chemistry records sea
temperature (oxygen
isotopes)
Coral core and X-ray with growth bands
slide/ coral core
and x-ray
oxygen isotope
Calibration curve
slide/ calibration curve of 18O
and SST in coral
two prolonged La Niña events
Oxygen isotope index
-5.3
-4.9
-4.5
-4.1
-3.7
1840
1860
1880
1900
1920
1940
1960
1980
2000
Period of instrumental data
Ice cores
•
•
•
•
volcanic eruptions - ashes
atmospheric gasses - small air bubbles
temperature - oxygen isotopes
windiness - dust
• http://www.pages.
unibe.ch/products/
overheads2/icecor
es.html
Greenhouse gasses in
ice cores
Some causes of climatic variation
•
•
•
•
Ocean circulation
Sunspots
Volcanic eruptions
Atmospheric conditions
– El Nino Southern Oscillation
Currents and climate
• Miller 2.167
Sunspots
• Dark spots (cool areas) that
move across the surface of
the sun*
• Every 11 years there is a
period called a “solar
maximum” with lots of
sunspots and solar flares
• Today’s sunspot number
http://www.sunspotcycle.com/
*But these dark areas are surrounded by hotter rings
that more than make up for the difference in radiation
Fewer sunspots seem to be associated with:
• lower
temperatures
• more severe
winters
• glacial
advances
Volcanoes
• blast gasses (sulfur dioxide) and ash into the
lower stratosphere.
• strong winds in stratosphere blow material
around the world.
• sulfur dioxide combines with water to for
sulfuric acid aerosols (fine droplets)
How does this affect climate?
Volcanic eruption
Volcanoes, cont.
• scatters incoming radiation back to space
• reduces heating of earth’s surface
• last up to four years
Mt Pinatubo, Philippines
Pinatubo sulfur dioxide cloud
June 17, 1991
June 19, 1991
Pinatubo sulfur dioxide cloud
Pinatubo stratospheric
aerosols
40 days before
40 days after
20 months after
• Average temperatures dropped by 0.2 to 0.5
oC for 1 to 3 years
El Niño – Southern Oscillation (ENSO)
• Oscillation of southern high and low pressure
zones
– Weakening of Peruvian high pressure zone
– Weakening of Indonesian low pressure zone
– Weakening of southeast trade winds
– Affects local climate
Sea surface temperatures off South America
Upwelling off South America
• 9.12a 2.209
El Niño sea temperature
El Niño year
• 9.12b 2.207
ENSO teleconnections –
affects on global climate
Segar, 1998
Past periods of climate change
• Medieval Warm Period
• Little Ice Age
Insert
temperature
recoreds
The Medieval Warm Period
• 1000 to 1300 AD
• regional warming (not necessarily global)
• Longer and warmer growing season
– grapes in England
• Higher treelines
• Warmer sea surface temperatures in North
Atlantic
• approx. 1o C warmer than present
Viking settlement on Iceland and Greenland
from 800 to 1200
The Little Ice Age
• Very cold climate between 1560 and 1890
• Greater frequency of storms
• Glacial advances 1560-1610,1816-1890
• Wheat prices higher
in Europe
• Paintings darker,
cloudier
Iceland
• Population declines in
Iceland indicated by tax
records
• shift from grains to
barley (short growing
season) to no grains
• fishing failed as fish
migrated southward due
to water temperatures.
• Height declines
– from 5’8” in 900s to 5’6”
in 1700s in Iceland
Iceland population
100000
barley no grain
0
1000
1200
1400
1600
1800
2000
Greenland
• 1300 highest
population (3000)
• Poor harvests,
fewer livestock
• Increase in sea ice
decreased trade
• Settlements
abandoned
• Height decrease
from 5’7” to < 5’ by
1400
Intro to activity: The Palmer Drought
Severity Index
Based on temperature, precipitation, and tree
ring records
• http://www.ngdc.noaa.gov/paleo/drought/drgh
t_pdsi.html
• http://www.ngdc.noaa.gov/paleo/pdsiyear.htm
l
Locations of tree rings
•http://www.ngdc.noaa.gov/paleo/pdsiyear.html
Pinatubo sulfur
dioxide cloud 3
months after
eruption
Little ice age
• glacial advances
http://www.ucar.edu/learn/1_2_1.htm
• for pollen, tree ring w/ fire scar
slide/ drilling coral
Drilling a massive
coral
Many pictures of paintings, wheat
prices, etc.
• http://www2.sunysuffolk.edu/mandias/lia
/little_ice_age.html