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/fact-sheets/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

slide/ calibration curve of 18O and SST in coral

Calibration curveo

xyg

en i

soto

pe tem

peratu

re (oC

)

two prolonged La Niña events

Oxy

gen

iso

top

e in

de

x

-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

Greenhouse gasses in ice cores

• http://www.pages.unibe.ch/products/overheads2/icecores.html

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

• 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 Iceland0

100000

1000 1200 1400 1600 1800 2000

barley no grain

Iceland populationIceland

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/drght_pdsi.html

• http://www.ngdc.noaa.gov/paleo/pdsiyear.html

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

Drilling a massive coral slide/ drilling coral

Many pictures of paintings, wheat prices, etc.• http://www2.sunysuffolk.edu/mandias/lia

/little_ice_age.html