Example Snowball Earth Several putative episodes between 750
Example: Snowball Earth • Several putative episodes between 750 Myr and 580 Myr ago. • Evidence controversial, but puzzling (e. g. , glaciers at sea level at the equator • Freeze-fry cycles (global mean temperature -40 C to 40 C !) Hoffman and Schragg, Sci. Am. 2000
50 Myr ago, Eocene warm period • How do you get crocodiles (cold-blooded) to survive through the polar night on Ellesmere Island (80 N)? • Or palm trees in Wyoming (interior of continents)? • CO 2 maybe 1000 to 1500 ppmv (estimate)
The last 70 Million years (Zachos et al. , Science 2001)
The Ice Ages • Long term cooling and cyclic ice ages over the last 4 Myr Time (Myr) d 18 O in ocean sediment (Proxy for global ice volume)
The Ice Ages
June insolation at 65 N (Wm-2) A wobbly planet (Milankovitch) Time (kyr)
The ice ages • Reconstruction of land sea ice 21, 000 years ago February July CLIMAP reconstruction
Changing ocean circulation in glacial times? Modern Phosphate, a nutrient Glacial Ocean water masses appear to Have different properties, but what does that imply bout ocean circulation
Different wildlife!
Ice sheet margin (northern Greenland)
What does an ice age look like? Puget sound lobe Ralph Haugerud Harvey Greenberg
Harvey Greenberg
Harvey Greenberg
Harvey Greenberg
Harvey Greenberg
Rapid Climate change? Proxy for temperature from the Greenland Ice Sheet warm ~10 o. C cool Large changes in annual mean temperature in ~50 years… Now the claim is less than 3 years (Steffenson et al. , 2008)
Seen elsewhere? Greenland temperature Sea surface temperature near Venezuala Atmos. methane
mid Holocene 5000 to 6000 yrs ago - Hippos in the Sahara Lamb: Climate, history, and the modern world
The little ice age ~1600 to ~1850 A Frost Fair on the Thames at Temple Stairs (1684) Abraham Hondius, 1684 Extensive advance of glaciers in Europe Long, severe winters Was it global?
The Pacific Decadal Oscillation Warm phase o. C Cool phase
Example of PDO impacts Mantua et al. , 1997
El-Nino Southern Oscillation Nino 3 index of Pacific sea surface temperatures
Climate impacts of ENSO are global
Sea surface temperatures
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