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The Global Carbon Cycle and its Relation to Global Climate David Archer, University of Chicago
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Airborne Fraction of Carbon Released Century timescale peak Millennial timescale tail Airborne fraction of fossil fuel CO 2
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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
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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.
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IPCC 2001 and earlier Summaries for Policymakers IPCC 2001 and earlier reports implied that global warming would last about a century.
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CO 2 + CO 3 = + H 2 O 2 HCO 3 - 10100 2000 M CO 2 uptake capacity is determined by CO 3 = Seawater pH Chemistry Concentration in seawater
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Atmosphere / Ocean Equilibrium 600 Gton C 1800 Gton C as CO 3 = Gton C = 10 15 g We expect a partitioning of ~1:3 between air and ocean
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Atmosphere / Ocean Equilibrium Airborne Fraction of CO 2 Slug 1000-2000 Gton 4000-5000 Gton Archer 200522%33% Lenton 200621-26%34% CLIMBER22%35% Goodwin 200724-26%40% Ridgwell 200731%
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Atmosphere / Ocean Equilibrium Affected by: changes in circulation biology ocean temperature saturating the carbonate ion buffer
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Neutralization by CaCO 3 CO 2 + CaCO 3 + H 2 O ==> Ca 2+ + 2 HCO 3 -
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How long does it take? Neutralization e-folding timescale Archer 20055-8kyr Lenton 2006500 - 1000 yr Ridgwell 20071-2 kyr Tyrell 20072-3 kyr
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Atm. / Ocean / CaCO 3 Equilibrium CO 2 + CO 3 = + H 2 O 2 HCO 3 - CaCO 3 Ca 2+ + CO 3 = Fossil CO 2
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Atm. / Ocean / CaCO 3 Equilibrium [CO 2 ] [CO 3 = ] [HCO 3 - ] 2 K2K1K2K1 = Restored by CaCO 3 equilibrium Increases by 2x fossil fuel release Proportional to pCO 2 (Henry’s law). Goes up ~ 10% of fossil CO 2 release
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The Silicate Weathering CO 2 Thermostat CaCO 3 Burial CO 2 CaO Subduction Weathering = function(climate) Metamorphosis
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0 200 400 600 800 1000 1200 1600 1800 1400 0 1 2 3 4 5 6 0100300500 200 400 pCO 2 °C kyr The long tail
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One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime: A Geochemical Joke
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One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime:100,000,000,000 kcal A Geochemical Joke
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Sea Level -150 -100 -50 50 100 5101520 Global Mean T, °C Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today Pliocene 3Myr ago
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Sea Level -150 -100 -50 50 100 5101520 Global Mean T, °C Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today Pliocene 3Myr ago IPCC Forecast Year 2100 Eventual change 100x higher than IPCC forecast for 2100
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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.
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Long thaw Intended for a “popular”- level audience
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Global carbon cycle Carbon cycle science for climate wonks
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Understanding the forecast Rocks-for-jocks level undergraduate textbook
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Open climate 101 Open access class video lectures on-line models quizzes and labs print out a useless non-certificate
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Climate crisis IPCC 2007 “Unofficial Guide” Working Groups 1 (mostly), plus 2 and 3
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Warming papers Classic scientific papers (1827-2008) with snarky commentary
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