Paleo Climate

PALEO-CLIMATOLOGY: using modern weather patterns to infer past modes of climate

CLIMATE CHANGE = f(G,S,O,A,V)


There are also strong interactions.
Example: historic CO2 forcing and global warming.


These five Forcing Functions vary in
SCALE, CYCLICITY, NOISE, AMPLITUDE, and LAG.

1. SCALE CAUSES

CHRONOLOGICAL SCALE
109 106 103 102 10 YR
    SOLAR





    GEOLOGIC


    VOLCANIC


    ATMOSPHERE




    ORBITAL


GEOGRAPHICAL SCALE
  Local  Regional  Global 
    SOLAR
    GEOLOGIC


    VOLCANIC

    ATMOSPHERE
    ORBITAL



2. CYCLICITY: PREDICTABILITY?
  1. Quasi-cyclical: insolation curves, Suess wiggles in 14C record
  2. Step-function: glaciations of Pleistocene, Permian
  3. Unidirectional: Atmospheric and solar evolution



3. NOISE: effects of forcing mechanisms are modified by other variables
  1. Higher-frequency climatic mechanisms
      LIA < Glacial/Interglacial cycles < Glaciations
  2. Non-climatically induced changes as noise
      soil development, plant migration

4. AMPLITUDE: climatic forcing functions vary in their strength, and climate changes have varied in magnitude. There was a tendency to believe that large changes were gradual and infrequent.
cf. Heinrich events.


5. INTERNAL DYNAMICS & LAG: time gaps between cause and effect
  1. delay between the forcing signal and the climatic response
    • feedbacks may be gradual and non-linear
    • Example: build up of ice sheet 7600 + 1700 yr after insolation change
    • Example: albedo difference Tundra vs. Boreal forest = 4 C (Gallimore and Kutzbach 1991.)

  2. delay between the forcing signal and the climatic response
    • lag between the climatic change proxy climatic indicator
    • climate > vegetation change > pollen

INTERACTION

tropical cooling during LGM




Paleo- Climate Readings

HOMEWORK