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The importance of longevity in a greenhouse gas as climate forcing. David Archer University of Chicago. Joseph Fourier. Joseph Fourier described the greenhouse effect in 1827. Memoires d l’Academie Royale des Sciences de l’Institute de France VIIII, 570-604 (1827).
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The importance of longevity in a greenhouse gas as climate forcing David Archer University of Chicago
Joseph Fourier Joseph Fourier described the greenhouse effect in 1827 Memoires d l’Academie Royale des Sciences de l’Institute de France VIIII, 570-604 (1827)
Energy Balance of a Bare Rock Tearth = 259 K = -14° C = 6°F
A Planet with an Atmosphere Tatm = 259 K Tearth = 303 K = 86° F
John Tyndall, 1859 John Tyndall discovered that CO2, H2O, and CH4 are greenhouse gases. O2 and N2 are not.
CO2 is a greenhouse gas Resting State Symmetric Stretch O C O C O O No Resting Dipole IR Inactive Asymmetric Stretch Bend C O O O C O -1 -1 2349 cm 660 cm
Svante Arrhenius Svante Arrhenius calculated that doubling CO2would warm the Earth by 4-6°C, in 1896
The water vapor feedback + W a t e r V a p o r F e e d b a c k W a t e r V a p o r C o n c e n t r a t i o n + T e m p e r a t u r e
The ice albedo feedback + I c e A l b e d o F e e d b a c I c e M e l t s + T e m p e r a t u r e
David Keeling David Keeling started measuring CO2 concentration in the atmosphere
Various public predictions of detectable human-caused warming by year 2000 Charney report and others
Climate forcings Only greenhouse gasforcing looks like therecent temperature rise. Crowley, 2000
What about phenomenaundreamed-of? The sun is good at pushing our climate buttons. Clouds? Humidity? “They blame CO2 because they can’t think of anything else.”
A detective story The Butler. Found holding a smoking gun next to the deceased. Forensics matches the gun with the bullets. The Chauffer. In Kentucky for sister’s wedding. “Can’t think of any way he could have done it.” To convict the Chauffer, we’d have to first unconvict the Butler.
Airborne fraction of fossil fuel CO2 Century timescale peak Airborne Fraction of Carbon Released Millennial timescale tail
IPCC 2001 and earlier Summaries for Policymakers IPCC 2001 and earlier reports implied that global warming would last about a century.
Everyone gets this wrong Rutledge 2011 Shindell, 2012 Ramanathan 2008
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
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.
Band saturation effect of IR absorbtion by CO2 emphasizes the 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
Seawater pH Chemistry CO2 + CO3= + H2O <--> 2 HCO3- 10 100 2000 mM Concentration in seawater CO2 uptake capacity is determined by CO3=
Atmosphere / Ocean Equilibrium 600 Gton C 1800 Gton C as CO3= We expect a partitioningof ~1:3 between air andocean Gton C = 1015 g
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%
Atmosphere / Ocean Equilibrium Affected by: changes in circulation biology ocean temperature saturating the carbonate ion buffer
Neutralization by CaCO3 CO2 + CaCO3 + H2O ==> Ca2+ + 2 HCO3-
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 Pulls the airborne fraction down to ~ 10%
The Silicate Weathering CO2 Thermostat Volcanic CO2 degassing CaSiO2 -> Ca2+ + SiO2 Weathering = function( CO2 ) Ca2+ + CO3= -> CaCO3 CaCO3 + SiO2 -> CaSiO2 + CO2 Burial + Subduction
The Silicate Weathering CO2 Thermostat CO2 >100,000 years Helps explain Carl Sagan’s “Faint Young Sun” paradox
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 -100 Last Glacial Maximum 20 kyr ago -150
Methane is about here CO2 is here
Methane is about here CO2 is here
Earth’s temperature response toradiative forcing RF Climate sensitivity: D T / D RF Upper 100m Time scale: 10 yrs Thermal bufferof the deepocean: Time scale 1000 yrs DeepOcean
CO2 vs. CH4 CO2 poses a “trap” for humanity, because of the time separation of the cause and the impacts, which will continue to worsen essentially forever. It’s like an ever-intensifying curse on our descendents, or planting a cancer. The climate impacts from CH4 peak and subside within a human timescale. “Good” cholesterol vs. “Bad” cholesterol?