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

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

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.

CO 2 + CO 3 = + H 2 O 2 HCO  M CO 2 uptake capacity is determined by CO 3 = Seawater pH Chemistry Concentration in seawater

Atmosphere / Ocean Equilibrium 600 Gton C 1800 Gton C as CO 3 = Gton C = g We expect a partitioning of ~1:3 between air and ocean

Atmosphere / Ocean Equilibrium Airborne Fraction of CO 2 Slug Gton Gton Archer %33% Lenton %34% CLIMBER22%35% Goodwin %40% Ridgwell %

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

Neutralization by CaCO 3 CO 2 + CaCO 3 + H 2 O ==> Ca HCO 3 -

How long does it take? Neutralization e-folding timescale Archer kyr Lenton yr Ridgwell kyr Tyrell kyr

Atm. / Ocean / CaCO 3 Equilibrium CO 2 + CO 3 = + H 2 O 2 HCO 3 - CaCO 3 Ca 2+ + CO 3 = Fossil CO 2

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

The Silicate Weathering CO 2 Thermostat CaCO 3 Burial CO 2 CaO Subduction Weathering = function(climate) Metamorphosis

pCO 2 °C kyr The long tail

One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime: A Geochemical Joke

One gallon of gasoline Usable energy: 2500 kcal Unwanted greenhouse energy over CO 2 lifetime:100,000,000,000 kcal A Geochemical Joke

Sea Level Global Mean T, °C Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today Pliocene 3Myr ago

Sea Level 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

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 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.

Long 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 ( ) with snarky commentary