Lecture 10 March 20, 2008

1. Lecture 10March 20, 2008 • Stump-the-Prof Qs from March 12 • Chapter 27: Ice Time • Chapter 28: The Mysterious Biped • Chapter 29: The Restless Ape • Chapter 30: Good Bye • Guest lecturer: Ginny Michaux on her polar expeditions and climate change

2. Stump-the-Prof Q’s fromWednesday, March 12

3. Potentially active super volcano sites. http://www.solcomhouse.com/yellowstone.htm

5. KNOWN ERUPTIONS (Estimates of the volume of erupted material are given in parentheses. Mt.St Helens ~ 1 km³; Tambora (1815) ~ 100 km³). “VEI”=Volcanic Explosivity Index (log scale for VEI 7 or higher, the volume ejected must be 1000 km³ or more) VEI 8 Category: * Lake Taupo, North Island, New Zealand - Oruanui eruption 26,500 years ago (1,170 km³) * Lake Toba, Sumatra, Indonesia - 75,000 years ago (2,800 km³)-->Volcanic winter or ‘Millennial Ice Age’, ~60% human population eradicted * Yellowstone Caldera, Wyoming, United States - 2.2 million years ago (2,500 km³) and 640,000 years ago (1,000 km³) * La Garita Caldera, Colorado, United States - Source of the truly enormous eruption of the Fish Canyon Tuff 27.8 million years ago (~5,000 km³) VEI-7 Category: see http://en.wikipedia.org/wiki/Supervolcano Note: For large flood basalt eruptions, see “large igneous province”, also categorized as ‘super volcanoes’, though not explosive.

8. How bacteria acquire immunity to antibiotics Spontaneous DNA mutation: e.g. Drug-resistant tuberculosis Microbial sex (called transformation): e.g. Penicillin-resistant gonorrhea Scariest: plasmid, that can flit from one type of bacterium to another and provide resistant to multiple antibiotics Following mutation in bacterial DNA, natural selection takes over.

9. What are the societal culprits? What will help? • Overuse & inappropriate use of antibiotics • Use of antibiotics in ‘factory farming’ of meat, fish • Poor sanitation in under-developed countries • Global mobility • To help: reverse first two, work on #3, develop new and more powerful drugs • Entirely new approach? • Wash your hands!

10. Some notes on evolution

12. Migration paths and the spread of Homo-XX “Out of Africa Again and Again”: research by Alan Templeton. Based on use of 13 haplotypes = long-lived chunks of genome, together with a fossil-calibrated molecular clock. 14,000 ya 50,000 ya 80--150,000 ya 420-840,000 ya 1.7 Mya [Taken from: “The Ancestor’s Tale” By Richard Dawkins]

13. Ice ages

14. Warmer Departure of 18O from normal, as measured in cores from ocean bottom sediments . Colder

15. Thousands of years before present (BP) Warmer Colder Thousands of years before present (BP)

17. Milankovitch cycles: change in eccentricity of Earth’s orbit around the Sun. Period about 96,000 years.

18. Milankovitch cycles: Obliquity of Earth’s rotation. Period about 41,000 years.

19. Milankovitch cycles: precession of Earth’s orbital axis. Period about 19-21,000 years.

20. Changes in Solar Insolation (amount of energy from Sun) over past 1 Million years due to Milankovitch cycles. About 15% Rough avg. About 10% Note: This is for a specific Latitude--65o North.

21. Milankovitch got it right!

22. CO2 from gas trapped in ice cores. T from 18O/16O ratio in ice cores. Time history of atmospheric CO2 concentration (on the left) and mean temperature (on the right). Note that T tracks CO2 concentration very closely. (Actually, CO2 lags T changes)

23. Milankovitch effect triggers, does not explain amplitude of ice ages • Insolation averaged over whole Earth not large enough to explain large effects (glaciation) • Most substantial effect is on the asymmetrical heating between Northern & Southern hemispheres • Going into Ice Age: more snow->more Solar energy reflected back to space->more snow, etc • Coming out of Ice Age, paleoclimate records show increase in CO2 and CH4 (lagging some 100s of years after insolation goes up) • CO2 from oceans, CH4 from ? (permafrost?) • Non-linear feedback --> instability • Not clear what eventually limits the fall/rise in T • Volcanoes undoubtedly play a role

24. Snowball Earth? Possible snowball Earth periods in the Proterozoic Example of computer simulation

26. Current warming NOT caused by Milankovitch • Next Milankovitch change expected in 25-50,000 years…a cooling • Atmospheric CO2 is rising ahead of rise in T, not following • Greenhouse effect and possibility of anthropogenic cause first put forward by Arhennius in 1896 • His calculations essentially correct • Modelers in 70s and 80s predicted warming trend seen now

27. Rise in CO2 clearly due primarily to fossil fuel burning • More than enough CO2 produced to explain the observed rise • Oceans growing more acidic • Therefore not the source • Probably a sink • Atmospheric O2 decrease consistent with CO2 rise, oxidation of carbonaceous material, not from volcanoes • 13C/12C decreasing as CO2 increasing • Therefore oxidation of biogenic material • 14C/12C also decreasing, so the biogenic source dead for >100,000 yrs --> fossil fuel

28. In previous warm ups, rise in T PRECEDED rise in CO2 by several 100 years. Now T and CO2 are tracking each other closely.