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Honors 1360 Planet Earth Last time: Origins of Life :

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

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Honors 1360 Planet Earth Last time: Origins of Life :

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  1. Honors 1360 Planet Earth Last time: Origins of Life: Obs: Minerals deposited before 2.2 Ga require ~ no O2 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 CO2-H2O photosynths) Hyp: Eukaryotic photosynths (and O2) 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 O2 and CO2… First glaciations coincide with first rise in O2; later glacial epochs with low CO2 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 CO2 Each Year • But the biological feedbacks are similar: • Ice core and other data suggest biological • feedbacks on CO2, Methane, SO2 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 CO2 emissions: Can we do it?

  3. Beginning ~1900 we changed the inputs: Bio-CO2 (+)  Ice Albedo (+) ~60 Gt/yr in; 60 Gt/yr out 8 Gt/yr CO2! Earth Climate System Solar Energy Bio-SO2 (+) Bio-CH4 (+) The PHYSICS of how an increase X in ppm atmospheric CO2 increases radiative forcing is well understood… The biological feedbacks are not.

  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 ↓ CO2; • 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 ↑ CO2 • by degassing • Marine organisms absorb 50 Gt C/yr! • Uptake is P, N, or Fe-limited • depending on where • Biological pump is insensitive to CO2 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)

  8. 1998 report from ncpa.org (a “free- market” think tank) looking at expected cost of Kyoto CO2 abatement: 1998 oil cost: (1995)$16.80 Today’s price: (1995)$68.21

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

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