Honors 1360 Planet Earth Last time: Origins of Life :

Honors 1360 Planet EarthLast time:Origins of Life: Obs: Minerals deposited before 2.2 Ga require ~ no O2 in the early atmosphereObs: 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 epochsObs: History of O2 and CO2… First glaciations coincide with first rise in O2; later glacial epochs with low CO2 periodsHyp: Life exerts a primary control over Earth’s climate!

05 December 2008

Honors 1360 Planet EarthLast 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?

EarthClimateSystem

Solar Energy

Ice Albedo (+)

Bio-CO2 (+)

Bio-SO2 (+)

Beginning ~1900 we changed the inputs:

Bio-CH4 (+)

The PHYSICS of how an increase X in ppm atmosphericCO2 increases radiative forcing is well understood…

The biological feedbacks are not.

8 G

t/yr

CO

2!

~60 Gt/yr in;60 Gt/yr out

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!

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!

BUT THIS IS A PRETTY STRONG CLUE:

Global Change: A Quick Review

(The most recent executive summary from the last month’s winners of the Nobel Peace Prize)

1998 report fromncpa.org (a “free-market” think tank)looking at expectedcost of KyotoCO2 abatement:

1998 oil cost:(1995)$16.80

Today’s price:(1995)$68.21

From “TheMcKinseyQuarterly”(online journal ofbusinessmanagementstrategy)