9.1 Paleoclimate
Paleoclimatology reconstructs past climates using proxy records. Understanding past climate helps constrain climate sensitivity and validate models.
Climate Proxies
Ice Cores
Direct air samples: CO₂, CH₄. δ¹⁸O for temperature. 800,000 years.
Tree Rings
Annual resolution. Width → precipitation/temperature. ~10,000 years.
Ocean Sediments
δ¹⁸O in forams → ice volume/temperature. Millions of years.
Corals
Sr/Ca, δ¹⁸O for SST. Monthly resolution, centuries.
Key Climate Events
- • Ice Ages: Milankovitch cycles (100, 41, 23 kyr periods)
- • PETM: +5-8°C, 56 Ma, massive carbon release
- • LGM: Last Glacial Maximum, 21 ka, -4°C global
- • Holocene: Last 11,700 years, relatively stable