Transcript Temperature anomaly ( o C)

A paleoperspective on the
carbon cycle-climate system
Fortunat Joos
Climate and Environmental Physics and
Oeschger Centre of Climate Change Research
University of Bern
The 14C inventory in
the Earth System:
a constraint on 14C production
Production = - Decay of 14C
= l 14NEarth
Decay rate: l=1/8267 yr
14C Inventory, 14N
Earth :mainly from data
Carbon Pools
Atmosphere
590 GtC  820 GtC
Fossil
5000 GtC
Vegetation/Soil
3000 to 4000 GtC
Ocean
38‘000 GtC
Sediments
Marine Biota
3 GtC
Dissolved Inorganic Carbon in the ocean
varies between 1.9 and 2.5 mmol/kg
Sarmiento and Gruber,
Ocean Biogeochemical Dynamics, 2006
mmol/kg
14C/12C
in the Earth System
Atmosphere
D14C~ 0 %o
Vegetation/Soil
D14C~ -15 %o
Ocean
D14C ~ - 152.2 %o
Reactive Sediments
( CaCO3, Organic)D14C~ -200 %o
 14C / 12C

( 13C  25)
D C
(1  2
)  1 1000permil
1000
 Rstd

14
permil
Observed Deep Ocean D14C
-50
14C/12C-ratio
varies in ocean
within 0.96 to 0.76
-150
-250
Simulated Deep Ocean D14C
in the Bern3D model
Müller, et al., J. Climate, 2005
An estimate:
Observation-based:
Ocean:
Atmosphere:
Model-supported:
CaCO3 Sediment
Organic Carbon Sediment
flux to litosphere · l
vegetation
soils
Total Inventory
14N
Earth
[1026 atoms]
20,010
(85%)
360
(2%)
350
170
920
(6%)
360
~1,500
(8%)
23,670 1026 atoms
(100%)
An estimate:
Total Inventory
14N
Earth
23,670 1026 atoms
Total Production: l 14NEarth = 9.079 1018 atoms s-1
= 1.78 atoms cm-2 s-1
Next steps:
• estimate transient effects
using the Bern3D model
(atmospheric variation
in 14C/12C: 6%) and
link to solar modulation
• improve terrestrial estimate
(peat and permafrost)
How do past changes in
radiative forcing compare with
ongoing forcing changes?
Cause effect chain:
Perturbation in radiative balance
feedbacks
Climate Change
Rates of Change
+4
-10
CO2 (ppm)
300
Temperature
anomaly (oC)
Atmospheric CO2 and Antarctic temperature
covaried over the past 800,000 years.
CO2 acts as an amplifying feedback
180
Today
800 ka BP
Age
(Lüthi et al., 2008)
Variations in Earth‘s orbit control seasonal and
latitudinal distribution of solar insolation
and likely caused glacial-interglacial cycles
Annual mean insolation
Time scales:
20,000 ++ years
Summer insolation
latitude
60 W/m2
10 W/m2
-500
Time kyr 0
100
-60 W/m2
(IPCC, 2007
Changes in greenhous gas concentration
and ice sheet growth acted as amplifying feedbacks
Radiative Forcing at the Last Glacial Maximum
Orbital: large distributional effects,
but small change in global annual mean insolation
(IPCC, 2007, Fig. 6.5)
Temperature response of the Bern model
to orbital, greenhouse gas and
ice sheet-albedo forcing
Orbital only
Global Temperature
(oC)
+16
Orbital + CO2 +ice
+10
800 ka BP
Today
(Ritz et al., 2010)
350
Time scale of 1increase:
decadal-to-century
300
0
250
Radiative Forcing (W m-2)
Carbon Dioxide (ppm)
Atmospheric CO2 is rising and far above the
preindustrial range: CO2 from anthropogenic
emissions causes warming and ocean acidification
Perturbation life time:
millennial
5000
10000
0
Time (years before present)
(IPCC, 2007, Fig. SPM-1a)
Rates of Change
Rates of climate change co-determine
severity of impacts on socio-economic and
natural systems
Rates of change over the past 22,000 years
inferred from splines through ice/atm. data
The rate of increase
in the combined
Potential Smoothing
radiative
forcing
of peak
in ice
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)
(Joos and Spahni, PNAS, 2008)
How do rates of change in
anthropogenic forcing compare
with solar and volcanic forcing of
the last millennium?
Rates of decadal-scale change:
Natural (solar, volcanoes) versus human made
volcanoes
Solar
(MM 0.25%)
sum of current
rates in
anthropogenic
forcings
Trend in solar
irradiance
over satellite period:
10-6 W m-2 yr-1
(Joos and Spahni, PNAS, 2008)
Last millennium:
Are suggestions of a small
influence of solar changes on
climate over
the past millennium plausible?
A carbon cycle-climate perspective
Data-based reconstructions
Today‘s solar activity is not unusual in the context
of the last millennium: solar modulation from 14C
tree ring record and carbon model
1600 AD
Muscheler et al., 2005
Different solar forcing reconstructions from
10Be,14C, sunspot records differ in amplitude
(not in evolution)
Volcanic, solar and other forcings
Bard et al., 2000
(MM: -0.25%)
1000
1500
Wang et al., 2005
(MM -0.08%)
2000
Year
(IPCC, 2007, Fig. 6.14)
Reconstructed ranges for low frequency
variations in NH temperature are
between ~ 0.3oC and 1oC
Temperature anomaly (oC)
Northern Hemisphere temperature reconstructions
(IPCC, 2007, Fig. TS-20)
800
1200
Year
1600
2000
Preindustrial CO2 variations:
an additional constraint
(Etheridge al.)
(Neftel al.)
Siegenthaler et al., 2004
Climate model results
Climate models forced with prescribed forcing
(low and high solar):
simulated versus reconstructed NH temperature
Temperature anomaly (oC)
Anthropogenic
Forcing
With
Without
1000
1400
1600 AD
Year
1800
(IPCC, 2007, Fig. 6.14)
Temperature anomaly (oC)
Simulated temperatures with and without anthropogenic
Aforcing
significant
of theorreconstructed
interdecadal
andfraction
with weak
strong solarNH
irradiance
variations
temperature variability over at least the seven centuries prior to
Anthropogenic
1950 is very likely attributable to volcanic eruptions and changes
in
Forcing
solar irradiance
1000
1400
Year
1800
(IPCC, 2007, Fig. 6.14)
Modelled versus measured CO2
Simulated atmospheric CO2
Simulated versus ice core CO2
versus ice core data
Model results: smoothed with DML age distribution
Probabilistic estimates of the
sensitivity of CO2 to temperature
from reconstructions
DCO2/DT (ppm/K)
Probability
A probabilistic assessment of the
CO2-temperature sensitivity based on
different temperature and CO2 reconstructions
0
20
40
60
Sensitivity (ppm per oC)
(Frank et al., 2010)
Comparison of data-based
estimates of the sensitivity of CO2
to temperature with model results
Probability
Reconstructed
20th century
C4MIP models
0
20
Sensitivity (ppm per oC)
(Range of median values)
40
(Frank et al.,2010)
• 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
High Solar Forcing
Large low frequency
temperature
variations are not
compatible with the
ice core CO2 record
Natural forcings: contribution to 20th century
warming is less than 0.15 K for all solar scalings