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

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

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

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.

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 andprovide resistant to multiple antibiotics

How bacteria acquire immunity to antibiotics

Following mutation in bacterial DNA, natural selection takes over.

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!

Some notes on evolution

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.

[Taken from: “The Ancestor’s Tale”By Richard Dawkins]

14,000 ya

80--150,000 ya

420-840,000 ya

1.7 Mya

50,000 ya

Ice ages

Departure of 18Ofrom normal, asmeasured in coresfrom ocean bottomsediments .

Warmer

Colder

Thousands of years before present (BP)

Thousands of years before present (BP)

Warmer Colder

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

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

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

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 specificLatitude--65o North.

Milankovitch got it right!

Time history of atmospheric CO2 concentration (on the left)and mean temperature (on the right). Note that T tracksCO2 concentration very closely. (Actually, CO2 lags T changes)

CO2 from gas trapped inice cores.

T from 18O/16O ratio inice cores.

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

Snowball Earth?

Example of computer simulation

Possible snowball Earth periods in the Proterozoic

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

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

In previous warm ups, rise in T PRECEDED rise in CO2 by several100 years. Now T and CO2 are tracking each other closely.