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Uncertainties in absolute attribution of climate change SB-24 17 May 2006. Joyce Penner University of Michigan. Overview of paper #2. Paper #1 examined the uncertainties associated with methodological choices in attributing relative temperature change

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uncertainties in absolute attribution of climate change sb 24 17 may 2006
Uncertainties in absolute attribution of climate changeSB-24 17 May 2006

Joyce Penner

University of Michigan

overview of paper 2
Overview of paper #2
  • Paper #1 examined the uncertainties associated with methodological choices in attributing relative temperature change
  • Here we assess scientific uncertainties in attributing absolute climate change
  • We use a closure method to evaluate uncertainties:
    • Emissions to concentrations for long lived greenhouse gases
    • Radiative forcing to temperature change for attribution
  • Attribution of OECD Annex I countries are used as an example because these (and their uncertainties) are available from UNFCCC reporting

Modelling and assessment of contributions to climate change

slide3

Overview of paper #2

Contributors:

Prather, Lowe, Raper, Stott, Höhne, Fuglestvedt,

Romstad, Penner, Andronova, Kurosawa, Wagner,

Jain, Pires de Campos, Meinshausen, van Aardenne

Modelling and assessment of contributions to climate change

method
Method

Global inventories of GHG emissions based on activities

Emissions

Match?

Emissions derived from atmospheric measurements

Total uncertainty of OECD Annex I countries contribution

Concentrations

All sources of historical radiative forcing

Radiative forcing

Match?

Observed temperature increase

Global average temperature change

Modelling and assessment of contributions to climate change

slide5

Example: N2O

Emissions from inverse

model are well within

the stated uncertainties

of the EDGAR data base

Emissions of OECD

Annex I countries from

EDGAR are within stated

uncertainties from

UNFCCC inventories

Modelling and assessment of contributions to climate change

slide6

We estimate a pdf

for OECD Annex I N2O emissions

using UNFCCC

uncertaintiesfor

the next step

(RF to T)

Modelling and assessment of contributions to climate change

slide7

Example: CH4

Global emissions from

Edgar bottom-up

inventory match well

the emissions required

to fit observations of

CH4.

But the Edgar OECD

Annex I emissions are

significantly higher than

the UNFCCC emissions.

The uncertainties for

UNFCCC emissions must

be increased in RF to T

calculations

Modelling and assessment of contributions to climate change

slide8

Uncertainties

in OECD Annex I

countries are

widened for

the next step

(RF to T) to

account for

mis-match between

EDGAR and

UNFCCC reported

emissions

Modelling and assessment of contributions to climate change

slide9
CO2

The increase in CO2 concentration can be explained by the following factors: Measured

  • Anthropogenic emissions from fossil fuels and industrial processes Well known
  • Anthropogenic emissions/removals from land use change and forestry Unknown
  • Natural removals by the biosphere Modelled
  • Natural removals by the ocean Modelled

Modelling and assessment of contributions to climate change

slide12

But UNFCCC LUCF emissions from OECD Annex I countries are outside the uncertainty range from inverse method: Need to increase range of uncertainty considered in RF to T calculation! (not yet included)

UNFCCC

LUCF

emissions

method1
Method

Global inventories of GHG emissions based on activities

Emissions

Match?

Emissions derived from atmospheric measurements

Total uncertainty of OECD Annex I countries contribution

Concentrations

All sources of historical radiative forcing

Radiative forcing

Match?

Observed temperature increase

Global average temperature change

Modelling and assessment of contributions to climate change

radiative forcing and uncertainty was estimated for all of the important climate factors
Radiative Forcing and uncertainty was estimated for all of the important climate factors *

Forcing (W/m2)

* Refers to preliminary assessment

Modelling and assessment of contributions to climate change

comparison of d and a inverse model aerosol forcing with bottom up aerosol forcing
Comparison of D and A (inverse model) aerosol forcing with bottom-up aerosol forcing

Bottom up method

yields wider uncertainty

range, but encompasses

inverse method

Modelling and assessment of contributions to climate change

uncertainty in natural forcing deduced using different reconstructions
Uncertainty in natural forcingdeduced using different reconstructions

Volcanic

Solar

Modelling and assessment of contributions to climate change

additional contributions from land use albedo change and dust based on tar estimates
Additional contributions from land use albedo change and dust – based on TAR estimates

Modelling and assessment of contributions to climate change

what will alter median and spread of bottom up forcing
What will alter median and spread of bottom up forcing?

Uncertainty range in bottom up forcing

Median magnitude of bottom up forcing

Forcing calculated to year 2000

Modelling and assessment of contributions to climate change

use uncertainties in individual components to define uncertainty in total forcing
Use uncertainties in individual components to define uncertainty in total forcing

Modelling and assessment of contributions to climate change

results space of modeled temperatures compared to observed warming since 1880
Results space of modeled temperatures compared to observed warming since 1880

Observations are shown in black

Modelling and assessment of contributions to climate change

slide21
Compare forcing from bottom up and forcing from inverse: not all forcing scenarios are consistent with the observed temperature change*

Forcing from bottom up estimates*

Forcing from inverse calculation

*Preliminary values

Modelling and assessment of contributions to climate change

method2
Method

Global inventories of GHG emissions based on activities

Emissions

Match?

Emissions derived from atmospheric measurements

Total uncertainty of OECD Annex I countries contribution

Concentrations

All sources of historical radiative forcing

Radiative forcing

Match?

Observed temperature increase

Global average temperature change

Modelling and assessment of contributions to climate change

effect of group s emissions
Effect of group’s emissions

Modelling and assessment of contributions to climate change

combined effect of uncertainties on warming from oecd annex 1 countries due to co 2
Combined effect of uncertainties on warming from OECD Annex 1 countries due to CO2

Combined effect of uncertainty in global mean forcing, climate sensitivity, ocean diffusivity and OECD Annex 1 forcing uncertainty on warming from OECD Annex 1 countries due to CO2

A likelihood was estimated for the unperturbed case using agreement with observed warming. The prior probability for the OECD Annex 1 perturbations was also included.

The fraction of warming attributable to OECD Annex I countries is 0.23 with a 95% confidence interval of 0.08 to 0.38.

combined effect of uncertainty on warming from oecd annex 1 countries due to co 2 ch 4 and n 2 o
Combined effect of uncertainty on warming from OECD Annex 1 countries due to CO2, CH4 and N2O*

Combined effect of uncertainty in global mean forcing, climate sensitivity, ocean diffusivity and

OECD Annex 1 forcing uncertainty on warming from OECD Annex 1 countries due to CO2, CH4,

and N2O

A likelihood was estimated for the unperturbed case using agreement with observed warming.

The prior probability for the annex 1 perturbations was also included.

The fraction of warming attributable to OECD Annex I countries is 0.34 with a 95%

confidence interval of 0.23 to 0.53. (*preliminary analysis)

conclusions
Conclusions
  • We examined uncertainties in emissions inventories for both global mean values and OECD Annex I GHG emissions
  • We examined the consistency between the emissions and observed concentrations
  • We estimated forcing and forcing uncertainty from all other known climate factors
  • We examined the implications of this uncertainty for predicted global average temperature change and the change associated with 1990 - 2002 OECD Annex I emissions

Modelling and assessment of contributions to climate change

closure for long lived greenhouse gases
Closure for long-lived greenhouse gases
  • Compare bottom-up inventories to those determined from inverse models to determine uncertainty in global emissions
  • Define OECD Annex I emissions using UNFCCC reported emissions and reported uncertainties
  • Compare OECD Annex I emissions from inverse model and adjust uncertainty in UNFCCC emissions if needed

Modelling and assessment of contributions to climate change

comparison of oecd annex i emissions with global emissions
Comparison of OECD Annex Iemissions with global emissions

Modelling and assessment of contributions to climate change

oecd annex 1 warming due to co 2 and effect of uncertainty in climate sensitivity
OECD Annex 1 warming due to CO2, and effect of uncertainty in climate sensitivity

Modelling and assessment of contributions to climate change

oecd annex 1 warming due to co 2 and effect of uncertainty in ocean diffusivity
OECD Annex 1 warming due to CO2, and effect of uncertainty in ocean diffusivity

Modelling and assessment of contributions to climate change

uncertainties in global mean forcing
Uncertainties in global mean forcing

Modelling and assessment of contributions to climate change

oecd annex 1 warming due to co 2 and effect of uncertainty in global mean forcing
OECD Annex 1 warming due to CO2, and effect of uncertainty in global mean forcing

Modelling and assessment of contributions to climate change

uncertainty in oecd annex 1 forcing from n 2 o
Uncertainty in OECD Annex 1 forcing from N2O

Modelling and assessment of contributions to climate change

combined effect of uncertainty on warming from oecd annex 1 countries due to n 2 o
Combined effect of uncertainty on warming from OECD Annex 1 countries due to N2O

Combined effect of uncertainty in global mean forcing, climate sensitivity, ocean diffusivity and OECD Annex 1 forcing uncertainty on warming from OECD Annex 1 countries due to N2O

A likelihood was estimated for the unperturbed case using agreement with observed warming. The prior probability for the OECD Annex 1 perturbations was also included.

The fraction of warming attributable to OECD Annex I countries is 0.015 with a 95% confidence interval of 0.0075 to 0.045.

uncertainty in oecd annex 1 forcing from ch 4
Uncertainty in OECD Annex 1 forcing from CH4

Modelling and assessment of contributions to climate change

combined effect of uncertainty on warming from oecd annex 1 countries due to ch 4
Combined effect of uncertainty on warming from OECD Annex 1 countries due to CH4

Combined effect of uncertainty in global mean forcing, climate sensitivity, ocean diffusivity and OECD Annex 1 forcing uncertainty on warming from annex 1 countries due to CH4

A likelihood was estimated for the unperturbed case using agreement with observed warming. The prior probability for the OECD Annex 1 perturbations was also included.

The fraction of warming attributable to OECD Annex I countries is 0.085 with a 95% confidence interval of 0.06 to 0.12.

comparison of aerosol forcing to year 2000 from bottom up with d and a reconstruction
Comparison of aerosol forcing to year 2000 from bottom-up with D and A reconstruction

Bottom-up reconstruction – used in subsequent analysis

D and A reconstruction

Modelling and assessment of contributions to climate change

inverse model used to estimate forcing for 2 different values of climate sensitivities
Inverse model used to estimate forcing for 2 different values of climate sensitivities

Time filtered forcing values

Annual values

Inverse calculation showing plume of forcing curves for different climate sensitivity based on TAR GCM models.

Modelling and assessment of contributions to climate change

slide40
Would need to add other forcings to make all scenarios from bottom up estimates consistent with observed T

pdf from inverse

pdf from bottom up

Minus

pdf of extra forcing that needs to be added to bottom up to achieve consistency with temperature record

Sample all combinations

Modelling and assessment of contributions to climate change