1. The last 600ky… LGM Last Glacial Maximum 18Ky

2. Paleoclimataology Lecture notes from Ellen Druffel

3. 1. Eccentricity 3% range of variation of E-S distance due to eliptical orbit around Sun, Pull of large planets Now, perihelion occurs during northern Winter (3 January) 100ky and 413ky periods Now, e =.0167 (relatively circular)

4. 2. Tilt - Reason for Seasons Now tilt is 23.5°, and is decreasing. Higher the tilt, higher the seasonal differences Has gone from 24.5° -22.2°, varied by pull of large planets 41 ky period

5. 3. Precession - Wobble Varies E-S distance with season Variation of the direction in which the E axis leans. Caused by the pull of Sun and moon on Earth Now Earth’s axis points to Polaris 23 ky stronger period - combined wobble and slow turning of eliptical orbit. Now 11Kya

6. On the long term…the precessional index Eccentricity variations at 100Ky and 413Ky modulate the amplitude of the precession cycle. This is why we have the 100Ky ice age cycle!

7. How orbital theory, climate records (  18 O) and northern hemisphere insolation (i.e. melting in N. Atlantic) compare over the past 600ky. Cold warm now LGM 18ky

10. BLAG invokes chemical weathering

11. Molnar & England, 1990