Explore the role of the ocean in affecting how warming relates to carbon emissions

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1 Climate impacts from the sequestration of heat & CO Talk plan: 1. Surface warming versus emissions. Response for long-term equilibrium 3. Response on multi-decadal timescale 4. Simplified atmosphere-ocean illustration IPCC (13) Allen et al. (9) Nature Peak warming link to cumulative carbon emissions Explore the role of the ocean in affecting how warming relates to carbon emissions Southern Ocean is potentially important player in affecting the anthropogenic heat and carbon uptake Phil Goodwin (Southampton), Ric Williams (Liverpool) & Andy Ridgwell (Bristol) (Goodwin, Williams & Ridgwell, 15, Nature Geoscience)

2 Climate response climate response after decades climate response after centuries Timescale: decades Q N = F R T F R Climate feedbacks Transient warming T Q N Large ocean heat uptake Timescale: centuries F Rfrom CO Very little ocean heat uptake Climate feedbacks Equilibrium warming S from Knutti and Hegerl (8)

3 1. Surface warming versus cumulative carbon emissions explore relationship between carbon emissions and warming T = T (t) T (t o ) = (t) (t o ) aim to reveal competing effects of ocean heat & carbon uptake R = R(t) R(t o ) avoid many important processes, such as other greenhouse gases, aerosols...

4 Temperature links to radiative forcing from CO surface warming change T = R T radiative forcing change absorption % absorption at ground level O O O O O visible 1. (b) absorption at 11 Km 1.5 radiative forcing from CO. 3. O 3 CO 5. Wavelength (μm) 1 15 R O O H O H O H O CO HOO N O H O O 3 N O CO O H O CO N O CO H O CH 4 CH 4 CO bands R = a ln(co (t)/co (t o )) O 3 H O (rotation) 3 5 climate feedback paramet 1 a =5.35Wm climate sensitivity from CO ln(co (t)/co (t o )) T = T CO ln climate feedback parameter 1 = T CO a ln T CO =1.5 to 4.5 K =.5 to 1. K(W m - ) -1

5 Atmospheric CO response to carbon emissions What is the effect of more CO? oceans become more acidic inhibits further ocean uptake reactions in seawater CO (t equilib )=CO (t o )exp( / ) = (t) (t o ) = I Atmos + C sat /B is 35 PgC ln CO = Goodwin et al. (7) GBC Goodwin et al. (9) Nature Geoscience

6 . Climate response as air-sea equilibrium is approached F Climate feedbacks Timescale: centuries Very little ocean heat uptake Equilibrium warming S T = 1 R a =5.35W m R = a ln CO ln CO = ln CO =lnco (t) ln CO (t o ) = 35 PgC 1 a T = T/ 1. +/-.7 K per 1 PgC Williams et al. (1) GRL

7 Climate response climate response after decades climate response after centuries Timescale: decades Q N = F R T F R Climate feedbacks Transient warming T Q N Large ocean heat uptake Timescale: centuries F Rfrom CO Very little ocean heat uptake Climate feedbacks Equilibrium warming S from Knutti and Hegerl (8)

8 3. Climate response on multi-decadal timescales F Climate feedbacks Timescale: decades Q = F T Transient warming T Q Large ocean heat uptake warming dependence on radiative forcing from CO T = 1 ( R N) N ocean heat uptake efficacy T = 1 1 N R R normalised ocean heat uptake N = N R T = 1 (1 N ) R surface temperature change normalised ocean heat uptake radiative forcing from CO

9 3. Climate response on multi-decadal timescales for radiative forcing dependence on cumulative carbon emissions R = a ln CO ln CO (t) = R = a R = a radiative forcing from CO (t)+i Usat (t) 1+ I Usat (1 + I Usat) I normalised ocean carbon undersaturation cumulative emissions I Usat ocean carbon undersaturation normalised ocean carbon undersaturation Usat = I Usat (Goodwin et al. 15, Nature Geoscience)

10 (Goodwin et al. 15, Nature Geoscience) 3. Climate response on multi-decadal timescales for normalised ocean heat uptake surface temperature change T = 1 (1 N ) R R = a radiative forcing from CO normalised ocean heat uptake (1 + I Usat) normalised ocean carbon undersaturation radiative forcing from CO cumulative emissions N = N R normalised ocean carbon undersaturation I Usat = I Usat T = 1 (1 N ) a (1 + I Usat)

11 3. Climate response on multi-decadal timescales how does surface warming vary in time? (a) change in surface warming only due to ocean heat uptake inital response from emissions later response after emissions atmosphere increased radiative forcing from CO radiative forcing from CO (assume unchanged) surface ocean interior ocean surface warming ocean heat uptake increased surface warming reduced ocean heat uptake (b) change in radiative forcing only due to ocean carbon uptake surface warming increases in time due to weakening ocean heat uptake

12 3. Climate response on multi-decadal timescales how does radiative forcing vary in time? (b) change in radiative forcing only due to ocean carbon uptake inital response from emissions later response after emissions excess CO in atmosphere increased radiative forcing from CO ocean CO uptake ocean undersaturated in excess CO ocean CO uptake less excess CO in atmosphere more excess CO in ocean reduced radiative forcing from CO radiative forcing decreases in time due to ocean carbon uptake

13 3. Climate response on multi-decadal timescales Our tests of an atmosphere-ocean only (GENIE) model (a) 1st century surface warming from theory 5 T (K) Δ temperature change T (K) error Δ (b) discrepancy of surface warming (model minus theory).5 RCP 4.5 RCP 6. RCP 8.5 B1 IMAGE A1T MESSAGE B MESSAGE A1 AIM A ASF A1G MINICAM cumulative carbon emissions, (PgC) (Goodwin et al. 15, Nature Geoscience)

14 (Goodwin et al. 15, Nature Geoscience) Our tests of an atmosphere-ocean only (GENIE) model (a) cumulative carbon emissions 4 (1PgC) 3 1 I Usat (1PgC) ln CO Δ (b) ocean carbon undersaturation time (year) (b) ocean carbon undersaturation 3 B1 IMAGE A1T MESSAGE B MESSAGE A1 AIM A ASF 1 A1G MINICAM (c) change in ln CO time (year) (c) change in ln CO (d) percentage error in time lnco (year) % error in ln CO Δ 3 1 (d) percentage error in ΔlnCO with climate feedbacks without climate feedbacks time (year)

15 3. Climate response on multi-decadal timescales (Goodwin et al. 15, Nature Geoscience) surface warming increases in time due to weakening ocean heat uptake warming/ radiation (K [W m ] (b) surface warming dependence on radiative forcing ΔT / R (c) radiative forcing dependence time (year) on carbon emissions radiative forcing decreases in time due to ocean carbon uptake radiation/ emissions W m [1 PgC] 1 4 (c) radiative forcing dependence on carbon emissions R / ΔI time (year)

16 3. Climate response on multi-decadal timescales (Goodwin et al. 15, Nature Geoscience) The TCRE changes by factor over 5 years in the GENIE model T / (K [1 PgC] 1 ) Δ (c) warming response to carbon emissions (TCRE) (d) discrepancy in TCRE time (year) for model minus theory error in T / Δ (d) discrepancy in TCRE for model minus theory time (year) 1 ( 1 εn / R ) ( 1+I Usat / )

17 (Goodwin et al. 15, Nature Geoscience) Quantifying the Transient Climate Response to Emissions T = 1 (1 N ) a (1 + I Usat I ter) I ter change in terrestrial sink since preindustrial I ter = I ter / at 11, cumulative emissions 545 +/- 85 PgC atmospheric C increase 4 +/- 1 PgC ocean C increase 155 +/- 3 PgC terrestrial C increase 15 +/- 9 PgC.8 +/-. I ter I Usat ocean carbon undersaturation 797 +/- 3 PgC 1.5 +/-.4 I ter I Usat T/ 1.5 +/-.7 K per 1 PgC for atmosphere-ocean only 1.1+/-.5 K per 1 PgC for atmosphere-ocean-terrestrial system For 1, based on synthesis of coupled CIMP4 terrestrial coupled models (Friedlingstein et al., 6) I ter normalised change in terrestrial sink for 1.7 to.14 implied terrestrial change from 11 to 1 in T/ is 1% to -1%

18 Conclusions T = 1 (1 N ) a (1 + I Usat I ter) thermal response anthropogenic carbon response (a) initial response to carbon emissions on decadal timescales atmosphere surface warming N R Δ T ocean heat uptake radiative forcing climate response warm atmosphere excess CO increased from emissions ocean uptake of CO low DIC upper ocean undersaturated T (K) Δ temperature change (a) 1st century surface warming from theory RCP 4.5 RCP 6. RCP 8.5 B1 IMAGE A1T MESSAGE B MESSAGE A1 AIM A ASF A1G MINICAM (b) discrepancy cumulative of surface carbon warming emissions, (model minus (PgC) theory) Goodwin, Williams & Ridgwell (15) depth thermocline heat uptake in deep ocean deep ocean undersaturated ocean cold ocean high DIC S. high latitude equator N. high latitude (b) upper ocean equilibrates with the atmosphere after decades to centuries The ocean heat uptake & carbon undersaturation partly compensate, helps determine how carbon emissions translate into global warming modified by terrestrial drawdown, other greenhouse gases, aerosols... Ventilation in the Southern Ocean is likely to play a particularly important role. Multidecadal variability in this relationship likely to be mainly from the heat flux