1. Honors 1360 Planet Earth Last time: Origins of Life: Obs : Minerals deposited before 2.2 Ga require ~ no O 2 in the early atmosphere Obs : Organisms “near the roots” of the DNA tree tend to be hyperthermophilic & use methane or hydrogen plus reduced metals for energy (not CO 2 -H 2 O photosynths) Hyp : Eukaryotic photosynths (and O 2 ) become sufficiently commonplace to change the atmosphere ~ 2.2 Ga! Life & Climate: Obs : Faint young sun paradox: Early sun was weaker, but glaciation observed only in a few (later) short epochs Obs : History of O 2 and CO 2 … First glaciations coincide with first rise in O 2 ; later glacial epochs with low CO 2 periods Hyp : Life exerts a primary control over Earth’s climate! 05 December 2008

2. Honors 1360 Planet Earth Last time (Cont’d): Life on Earth & Climate Feedbacks The Forcing is Different Now than in the Past: ~13% of the Global Annual Respiration Cycle Is Removed from Storage in Sedimentary Rocks and Added to Atmospheric CO 2 Each Year But the biological feedbacks are similar: Ice core and other data suggest biological feedbacks on CO 2, Methane, SO 2 are all positive: Higher temperature leads to higher concentrations of greenhouse gas until a new “stability” is reached. Today: A quick review of global change from the IPCC Enough dire & dour, gloom & doom: Reducing CO 2 emissions: Can we do it?

3. Earth Climate System Solar Energy Ice Albedo (+) Bio-CO 2 (+) Bio-SO 2 (+) Beginning ~1900 we changed the inputs: Bio-CH 4 (+) The PHYSICS of how an increase X in ppm atmospheric CO 2 increases radiative forcing is well understood… The biological feedbacks are not.  8 Gt/yr CO 2 ! ~60 Gt/yr in; 60  Gt/yr out

4. Biological feedbacks on modern climate: IPCC: On Land Changes in Land Surface (vegetation, soils, water) change radiation (albedo), cloudiness, surface temperature Changes in surface vegetation change water, energy dynamics. Boreal forest reduces albedo (warms)… Increased temperature may increase or slow both photosynthesis or respiration: Depends on Soil Moisture Ecosystem shifts may ↑ or ↓ CO 2 ; ecosystem models predict long-term net ↑ storage of C but short-term vegetative die-back may release large amounts C if changes are rapid Evidence for growth of the net natural land carbon sink (0.3 GtC/yr in 1980’s, 1.0 GtC/yr in 1990’s) Net Uncertain!

5. IPCC: Oceans 1ºC increase in sea surface temperature → 10 ppm ↑ CO 2 by degassing Marine organisms absorb 50 Gt C/yr! Uptake is P, N, or Fe-limited depending on where Biological pump is insensitive to CO 2 concentrations but may be sensitive to temperature, cloud cover, currents, UV, acidity… Net Uncertain!

6. BUT THIS IS A PRETTY STRONG CLUE:

7. Global Change: A Quick Review (The most recent executive summary from the last month’s winners of the Nobel Peace Prize)

14. 1998 report from ncpa.org (a “free- market” think tank) looking at expected cost of Kyoto CO 2 abatement: 1998 oil cost: (1995)$16.80 Today’s price: (1995)$68.21

15. From “The McKinsey Quarterly” (online journal of business management strategy)