A paleoperspective on the

carbon cycle-climate systemFortunat Joos

Climate and Environmental Physics and Oeschger Centre of Climate Change Research

University of Bern

The The 1414C inventory inC inventory inthe Earth System: the Earth System:

a constraint on a constraint on 1414C productionC production

Production = - Decay of Production = - Decay of 1414CC = = 1414NNEarthEarth

Decay rate:Decay rate:=1/8267 yr=1/8267 yr1414C Inventory, C Inventory, 1414NNEarth Earth :mainly from data:mainly from data

Atmosphere 590 GtC 820 GtC

Vegetation/Soil 3000 to 4000 GtC

Marine Biota3 GtCOcean

38‘000 GtC

Sediments

Carbon Pools

Fossil5000 GtC

Dissolved Inorganic Carbon in the ocean varies between 1.9 and 2.5 mmol/kg

mol/kgSarmiento and Gruber, Ocean Biogeochemical Dynamics, 2006

Atmosphere 14C~ 0 %o

Vegetation/Soil 14C~ -15 %o

Ocean14C ~ - 152.2 %o

Reactive Sediments ( CaCO3, Organic)14C~ -200 %o

14C/12C in the Earth System

14 12 1314 / ( 25)

(1 2 ) 1 1000permil1000std

C C CC

R

Observed Deep Ocean 14C

Müller, et al., J. Climate, 2005

-50

-150

-250

permil

Simulated Deep Ocean 14C

in the Bern3D model

14C/12C-ratio varies in ocean within 0.96 to 0.76

An estimate:An estimate:

Observation-based:Observation-based: [10 [102626 atoms] atoms]Ocean: Ocean: 20,010 20,010 (85%)(85%)Atmosphere:Atmosphere: 360 360 (2%)(2%)

Model-supported:CaCO3 Sediment 350 Organic Carbon Sediment 170flux to litosphere · 920 (6%)

vegetation 360soils ~1,500 (8%)

Total Inventory 1414NNEarthEarth 23,670 10 23,670 1026 26 atomsatoms

(100%)(100%)

An estimate:An estimate:Total Inventory 1414NNEarthEarth 23,670 1023,670 1026 26 atomsatoms

Total Production: Total Production: 1414NNEarth Earth = 9.079 10= 9.079 1018 18 atoms satoms s-1-1

= 1.78 atoms cm= 1.78 atoms cm-2 -2 ss-1-1

Next steps: Next steps: • estimate transient effects estimate transient effects using the Bern3D modelusing the Bern3D model (atmospheric variation (atmospheric variation in in 1414C/C/1212C: 6%) and C: 6%) and link to solar modulationlink to solar modulation

• improve terrestrial estimate improve terrestrial estimate (peat and permafrost)(peat and permafrost)

How do past changes in How do past changes in radiative forcing compare withradiative forcing compare with

ongoing forcing changes?ongoing forcing changes?

Cause effect chain:Cause effect chain: Perturbation in radiative balancePerturbation in radiative balance

feedbacksfeedbacks

Climate ChangeClimate Change

Rates of ChangeRates of Change

CO

2 (p

pm

) Tem

per

atu

re

ano

mal

y (o

C)

180180

300300 -10-10

+4+4

TodayToday 800 ka BP800 ka BPAgeAge

Atmospheric CO2 and Antarctic temperature covaried over the past 800,000 years. CO2 acts as an amplifying feedback

(Lüthi et al., 2008)

(IPCC, 2007-500-500 00 100100Time kyrTime kyr

lati

tud

ela

titu

de

Summer insolation Summer insolation

Variations in Earth‘s orbit control seasonal and latitudinal distribution of solar insolation and likely caused glacial-interglacial cycles

60 W/m60 W/m22

-60 W/m-60 W/m22

Annual mean insolation Annual mean insolation

Time scales: 20,000 ++ years

10 W/m10 W/m22

(IPCC, 2007, Fig. 6.5)

Changes in greenhous gas concentration and ice sheet growth acted as amplifying feedbacks

Radiative Forcing at the Last Glacial Maximum Radiative Forcing at the Last Glacial Maximum

Orbital: large distributional effects, but small change in global annual mean insolation

Temperature response of the Bern model to orbital, greenhouse gas and ice sheet-albedo forcing

Glo

bal

Tem

per

atu

re

(oC

)

++1010

+16+16

TodayToday800 ka BP800 ka BP(Ritz et al., 2010)

Orbital only

Orbital + CO2 +ice

(IPCC, 2007, Fig. SPM-1a)

Time (years before present)Time (years before present)001000010000 50005000

300300

250250

350350

Car

bo

n D

ioxi

de

(pp

m)

Car

bo

n D

ioxi

de

(pp

m)

Rad

iati

ve F

orc

ing

(W

mR

adia

tive

Fo

rcin

g (

W m

-2-2))

00

11

Atmospheric CO2 is rising and far above the preindustrial range: CO2 from anthropogenic emissions causes warming and ocean acidification

Time scale of increase:decadal-to-century

Perturbation life time:millennial

Rates of climate change co-determine severity of impacts on socio-economic and natural systems

Rates of ChangeRates of Change

(Joos and Spahni, PNAS, 2008)

Potential Smoothingof peak in ice

Rates of change over the past 22,000 years inferred from splines through ice/atm. data

The rate of increase

in the combined

radiative forcing

from CO2, CH4 and

N2O during the

industrial era is very

likely to have been

unprecedented in

more than 10,000

years (IPCC, SPM,

2007)

How do rates of change in anthropogenic forcing compare with solar and volcanic forcing of the last millennium?

(Joos and Spahni, PNAS, 2008)

volcanoes

Solar (MM 0.25%)

sum of currentrates in anthropogenicforcings

Trend in solar irradianceover satellite period:10-6 W m-2 yr-1

Rates of decadal-scale change: Natural (solar, volcanoes) versus human made

Last millennium:Last millennium:Are suggestions of a small Are suggestions of a small

influence of solar changes on influence of solar changes on climate overclimate over

the past millennium plausible?the past millennium plausible?

A carbon cycle-climate perspectiveA carbon cycle-climate perspective

Data-based reconstructionsData-based reconstructions

Muscheler et al., 2005

Today‘s solar activity is not unusual in the contextof the last millennium: solar modulation from 14C tree ring record and carbon model

1600 AD

Different solar forcing reconstructions from10Be,14C, sunspot records differ in amplitude (not in evolution)

1000 2000200015001500

(IPCC, 2007, Fig. 6.14)

YearYear

Volcanic, solar and other forcingsVolcanic, solar and other forcings

Bard et al., 2000 (MM: -0.25%)

Wang et al., 2005(MM -0.08%)

800 2000200012001200 16001600

(IPCC, 2007, Fig. TS-20)

Northern Hemisphere temperature reconstructionsNorthern Hemisphere temperature reconstructions

YearYear

Te

mp

era

ture

an

om

aly

(T

em

pe

ratu

re a

no

mal

y (

ooC

)C

) Reconstructed ranges for low frequencyvariations in NH temperature are between ~ 0.3oC and 1oC

Siegenthaler et al., 2004

(Etheridge al.)(Neftel al.)

Preindustrial CO2 variations: an additional constraint

Climate model resultsClimate model results

WithWith

WithoutWithout

Anthropogenic Anthropogenic ForcingForcing

(IPCC, 2007, Fig. 6.14)

1000 14001400 18001800YearYear

Te

mp

era

ture

an

om

aly

(T

em

pe

ratu

re a

no

mal

y (

ooC

)C

) Climate models forced with prescribed forcing (low and high solar): simulated versus reconstructed NH temperature

1600 AD

Anthropogenic Anthropogenic ForcingForcing

(IPCC, 2007, Fig. 6.14)

Simulated temperatures with and without anthropogenic Simulated temperatures with and without anthropogenic forcing and with weak or strong solar irradiance variationsforcing and with weak or strong solar irradiance variations

1000 14001400 18001800YearYear

Te

mp

era

ture

an

om

aly

(T

em

pe

ratu

re a

no

mal

y (

ooC

)C

) A significant fraction of the reconstructed NH interdecadal

temperature variability over at least the seven centuries prior to

1950 is very likely attributable to volcanic eruptions and changes in

solar irradiance

Modelled versus measured COModelled versus measured CO22

Simulated atmospheric CO2

versus ice core data

Model results: smoothed with DML age distribution

Simulated versus ice core CO2

Probabilistic estimates of the Probabilistic estimates of the sensitivity of COsensitivity of CO22 to temperature to temperature

from reconstructionsfrom reconstructions

COCO22//T (ppm/K)T (ppm/K)

A probabilistic assessment of the CO2-temperature sensitivity based on different temperature and CO2 reconstructions

0 20 40 60

Pro

bab

ilit

y

(Frank et al., 2010)

Sensitivity (ppm per oC)

Comparison of data-based Comparison of data-based estimates of the sensitivity of COestimates of the sensitivity of CO22

to temperature with model resultsto temperature with model results

0 20 40

Pro

bab

ilit

y

(Frank et al.,2010)Sensitivity (ppm per oC)(Range of median values)

Reconstructed

20th century C4MIP models

• The amplitudes of the preindustrial decadal-scale

Northern Hemisphere temperature changes from the

proxy-based reconstructions (<1oC) are broadly

consistent with the ice core CO2 record and our

quantitative understanding of the carbon cycle and

reconstructions of solar and volcanic forcing

• The small changes in CO2, CH4, and N2O over the

last millennium also suggest a limited range of

climate variability over this period

• A small solar influence on climate, despite large

variations in solar modulation, is consistent with the

climatic records of the last millennium

Thank you for your attention!

Surface temperature anomaly after a collapse of the North Atlantic Circulation

The power spectrum of the 14C and 10Be solar modulation records shows common peaks

Wanner et al., 2009

Low solar forcing: Simulated atmospheric CO2 versus ice core data

Model results: smoothed with DML age distribution

Large low frequency temperature variations are not compatible with the ice core CO2 record

High Solar Forcing

Natural forcings: contribution to 20th century warming is less than 0.15 K for all solar scalings