The Global Carbon Cycle and its Relation to Global Climate David Archer, University of Chicago
Airborne Fraction of Carbon Released Airborne fraction of fossil fuel CO 2 Century timescale peak Millennial timescale tail
Paleocene/Eocene Thermal Maximum Event 55 Myr Ago A natural release of CO 2, comparable to the potential fossil fuel release. Warming, with a recovery that took 100, 000 years. Zachos et al. 2001
Long Tail Model Intercomparison Project LTMIP D. Archer, M. l Eby, V. Brovkin, A. Ridgwell, L. Cao, U. Mikolajewicz, K. Caldeira, K. Matsumoto, G. Munhoven, A. Montenegro, Ann. Rev. Earth Sciences, 2009.
IPCC 2001 and earlier Summaries for Policymakers IPCC 2001 and earlier reports implied that global warming would last about a century.
Seawater p. H Chemistry CO 2 + CO 3= + H 2 O <--> 2 HCO 310 100 2000 m. M Concentration in seawater CO 2 uptake capacity is determined by CO 3=
Atmosphere / Ocean Equilibrium 600 Gton C 1800 Gton C as CO 3= We expect a partitioning of ~1: 3 between air and ocean Gton C = 1015 g
Atmosphere / Ocean Equilibrium Airborne Fraction of CO 2 Slug 1000 -2000 Gton Archer 2005 Lenton 2006 CLIMBER Goodwin 2007 Ridgwell 2007 22% 21 -26% 22% 24 -26% 4000 -5000 Gton 33% 34% 35% 40% 31%
Atmosphere / Ocean Equilibrium Affected by: changes in circulation biology ocean temperature saturating the carbonate ion buffer
Neutralization by Ca. CO 3 CO 2 + Ca. CO 3 + H 2 O ==> Ca 2+ + 2 HCO 3 -
How long does it take? Neutralization e-folding timescale Archer 2005 Lenton 2006 Ridgwell 2007 Tyrell 2007 5 -8 kyr 500 - 1000 yr 1 -2 kyr 2 -3 kyr
Atm. / Ocean / Ca. CO 3 Equilibrium Fossil CO 2 + CO 3= + H 2 O Ca. CO 3 Ca 2+ + CO 3= 2 HCO 3 -
Atm. / Ocean / Ca. CO 3 Equilibrium Proportional to p. CO 2 (Henry’s law). Goes up ~ 10% of fossil CO 2 release Restored by Ca. CO 3 equilibrium K 2 [CO 2] [CO 3=] = [HCO 3 -]2 K 1 Increases by 2 x fossil fuel release
The Silicate Weathering CO 2 Thermostat CO 2 Weathering = function(climate) Ca. O Ca. CO 3 Burial Subduction Metamorphosis
p. CO 2 The long tail 1800 1600 1400 1200 1000 800 600 400 200 0 6 °C 5 4 3 2 1 0 0 100 200 300 kyr 400 500
A Geochemical Joke One gallon of gasoline Usable energy: Unwanted greenhouse energy over CO 2 lifetime: 2500 kcal
A Geochemical Joke One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime: 100, 000, 000 kcal
Sea Level, m 100 Eocene 40 Myr ago 50 Global Mean T, °C 5 Today 10 15 -50 Last Glacial Maximum 20 kyr ago Pliocene 3 Myr ago -100 -150 20
Sea Level, m 100 Eocene 40 Myr ago 50 Global Mean T, °C 5 Today 10 15 -50 Last Glacial Maximum 20 kyr ago Pliocene 3 Myr ago -100 -150 IPCC 20 Forecast Year 2100 Eventual change 100 x higher than IPCC forecast for 2100
Conclusions The climate impacts of fossil fuel CO 2 release will persist for millennia. Sea level rise could ultimately be 100 times greater than the IPCC forecast for the year 2100. The carbon cycle on century timescales in the past has acted as an amplifier of climate change. So far, the carbon cycle today has been absorbing carbon (stabilizing feedback), but this could change.
g thaw Intended for a “popular”level audience
Global carbon cycle Carbon cycle science for climate wonks
Understanding the forecast Rocks-for-jocks level undergraduate textbook
Open climate 101 Open access class video lectures on-line models quizzes and labs print out a useless non-certificate
Climate crisis IPCC 2007 “Unofficial Guide” Working Groups 1 (mostly), plus 2 and 3
Warming papers Classic scientific papers (1827 -2008) with snarky commentary
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