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12 Paleoclimatology

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(12) Paleoclimatology. Relevance and the ideal paleo record ... Anemometer 1846. Modern hygrometer 1820. Thermometer 1600s. Barometer 1643. Rain gage 1442 ... – PowerPoint PPT presentation

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Title: 12 Paleoclimatology


1
(12) Paleoclimatology
  • Relevance and the ideal paleo record
  • Methods used in reconstructing the past
  • A brief history of the past 1,000,000 years
  • (Principles of Climatology GEOG31064-Sheridan)

2
Why study paleoclimatology?
  • Understanding the past understanding the future
  • Help improve climate models
  • Understand what caused shifts in the past
  • Understand how humans have influenced the climate
    system

3
What methods do we use?
  • Satellite
  • Instrumental records
  • Historical records
  • Proxy records

4
What makes an ideal paleo record?
  • Quantitative measurement
  • Global coverage
  • Continuous record
  • Small timescale

5
Satellites
  • First Microwave Sounding Unit (MSU) launched in
    late 1978
  • Measurements of precipitation, water vapor,
    temperature, radiation balance
  • Positives?
  • Negatives?

6
Instrument record
  • How far back do instruments go?
  • Wind vane 1500s
  • Anemometer 1846
  • Modern hygrometer 1820
  • Thermometer 1600s
  • Barometer 1643
  • Rain gage 1442

7
Problems with the data?
  • Exposure!
  • Accuracy warping glass
  • Scales 77 temperature scales in use in 1792
  • Spatial scale?
  • What can go wrong with a temperature value over
    time?

8
Reliable records
  • CET (Central England Temperature) 1659
  • London rainfall records 1697
  • Reliable global records
  • Temperature 1880
  • Sea level 1900
  • Surface ocean temperature 1930
  • Atmospheric composition 1960

9
Continuous historical records
  • Weather diaries back to 1300s
  • Fur-trading posts breakup of ice to 1600s
  • Crop prices
  • Japanese records of Cherry Blossom emergence to
    800

10
Other historical records
  • Nile floods go back to 622, intermittently to
    3000 BC
  • Droughts, frosts, floods, heat waves
  • Art and archaeology
  • Problems?

11
Proxy records
  • Use understanding of chemical, physical,
    biological processes to interpret climate
  • Biological biogeography (organism range)
  • Physical Physical processes (glacial deposition,
    isostatic rebound)
  • Chemical isotopes

12
Sediments
  • Continental location, carried to a quieter locale
    (usually under water)
  • Interruptions?
  • Land records 170My

13
What is in the sediment
  • Carbon decay (C14 to C12)
  • Pollen and plant debris
  • Animal (insect) remains
  • Quantity of sediment

14
Ice cores
  • Continuous accrual up to 400,000 yr
  • CO2 and CH4 trapped in ice
  • O16 to O18 ratio

15
Trees and corals
  • Growth rates can be analyzed annually

16
Questions
  • A growing glacier is indicative of what?
  • Is a sea-level rise the sea rising or the land
    sinking?
  • Why did a tree not grow well?
  • How spatially cohesive are the results?

17
Climate history
  • Early climate history warmer (more CO2)
  • Always liquid H2O on the planet

18
The past half million years
19
Temp changes from LGM to today
Aug
Feb
20
Melting of the Laurentide
21
Melting of the Laurentide
22
Younger Dryas
23
Circulation changes
24
More recent shifts
25
The Medieval Climate Optimum and the Little Ice
Age
26
Central England Temperature record
27
Causes of long term changes
  • Continental shifts
  • Atmospheric composition
  • Solar variability
  • Impacts of catastrophic events
  • Orbital cycles
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