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The Global Carbon Cycle and its Relation to Global Climate

This informative text explores the global carbon cycle and its impact on global climate, discussing topics such as fossil fuel CO2 release, seawater chemistry, the long-term effects of climate change, and more.

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The Global Carbon Cycle and its Relation to Global Climate

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  1. The Global Carbon Cycle and its Relation to Global Climate David Archer, University of Chicago

  2. Airborne fraction of fossil fuel CO2 Century timescale peak Airborne Fraction of Carbon Released Millennial timescale tail

  3. Paleocene/Eocene Thermal Maximum Event 55 Myr Ago A natural releaseof CO2, comparableto the potential fossil fuel release. Warming, with a recovery that took100,000 years. Zachos et al. 2001

  4. 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.

  5. IPCC 2001 and earlier Summaries for Policymakers IPCC 2001 and earlier reports implied that global warming would last about a century.

  6. Seawater pH Chemistry CO2 + CO3= + H2O <--> 2 HCO3- 10 100 2000 mM Concentration in seawater CO2 uptake capacity is determined by CO3=

  7. Atmosphere / Ocean Equilibrium 600 Gton C 1800 Gton C as CO3= We expect a partitioningof ~1:3 between air andocean Gton C = 1015 g

  8. Atmosphere / Ocean Equilibrium Airborne Fraction of CO2 Slug 4000-5000Gton 1000-2000Gton Archer 2005 22% 33% Lenton 2006 21-26% 34% CLIMBER 22% 35% Goodwin 2007 24-26% 40% Ridgwell 2007 31%

  9. Atmosphere / Ocean Equilibrium Affected by: changes in circulation biology ocean temperature saturating the carbonate ion buffer

  10. Neutralization by CaCO3 CO2 + CaCO3 + H2O ==> Ca2+ + 2 HCO3-

  11. How long does it take? Neutralization e-folding timescale Archer 2005 5-8kyr Lenton 2006 500 - 1000 yr Ridgwell 2007 1-2 kyr Tyrell 2007 2-3 kyr

  12. Atm. / Ocean / CaCO3 Equilibrium Fossil CO2 CO2 + CO3= + H2O 2 HCO3- CaCO3 Ca2+ + CO3=

  13. Atm. / Ocean / CaCO3 Equilibrium [CO2] [CO3=] [HCO3-]2 K2 K1 Proportional to pCO2 (Henry’s law). Goes up ~ 10% of fossil CO2release Restored by CaCO3 equilibrium = Increases by 2x fossil fuel release

  14. The Silicate Weathering CO2 Thermostat CO2 Weathering = function(climate) CaO CaCO3 Burial Subduction Metamorphosis

  15. The long tail 1800 1600 1400 1200 pCO2 1000 800 600 400 200 0 6 5 °C 4 3 2 1 0 0 100 300 400 500 200 kyr

  16. A Geochemical Joke One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO2 lifetime:

  17. A Geochemical Joke One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO2 lifetime: 100,000,000,000 kcal

  18. Sea Level Sea Level, m 100 Eocene 40 Myr ago 50 Pliocene 3 Myr ago Global Mean T, °C Today 5 10 15 20 -50 -100 Last Glacial Maximum 20 kyr ago -150

  19. Sea Level Sea Level, m 100 Eocene 40 Myr ago 50 Pliocene 3 Myr ago Global Mean T, °C Today IPCC 5 10 15 20 Forecast Year 2100 -50 Eventual change100x higher thanIPCC forecast for2100 -100 Last Glacial Maximum 20 kyr ago -150

  20. Conclusions The climate impacts of fossil fuel CO2 releasewill persist for millennia. Sea level rise could ultimately be 100 times greaterthan 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.

  21. Long thaw Intended for a “popular”-level audience

  22. Global carbon cycle Carbon cycle sciencefor climate wonks

  23. Understanding the forecast Rocks-for-jocks levelundergraduate textbook

  24. Open climate 101 Open access class video lectures on-line models quizzes and labs print out a useless non-certificate

  25. Climate crisis IPCC 2007 “Unofficial Guide” Working Groups 1 (mostly), plus 2 and 3

  26. Warming papers Classic scientific papers (1827-2008) with snarky commentary

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