uncertainties in climate change · pdf filehadley centre for climate prediction and research 1...

1Hadley Centre for Climate Prediction and Research

OECD Workshop on the benefits of climate policy.Paris, 12/13 December 2002

UNCERTAINTIES IN CLIMATECHANGE PREDICTIONS

Geoff JenkinsHadley CentreMet Office, UK


CLIMATE CHANGE DEPENDS UPON:

• How man-made emissions grow

– population, GDP, energy use, technology...

• How sensitive the climate system is to

emissions

– how much concentrations change

– what forcing effect this has

– what climate change this produces

– we can estimate this only with climate models


UNCERTAINTIES IN CLIMATEPREDICTIONS

EMISSIONS

CONCENTRATIONS

FORCING

GLOBAL CLIMATE

REGIONAL CLIMATE

IMPACTS, COSTS etc

NATURAL VARIABILITY

feedb

acks

• Emissions uncertainty

• “Science” uncertainty

• Natural variability


CO2 in SRES EMISSIONS SCENARIOS

A1FIA2B1B2


GLOBAL TEMPERATURE RISEG

lob

alte

mp

erat

ure

rise

,deg

rees

C IPCC A1FI emissionsA2 emissionsB2 emissionsB1 emissions

Start to divergefrom mid-century

HadCM3


UNCERTAINTY IN CO2CONCENTRATIONS

1000

850

700

550

400

2000 2025 2050 2075 2100

975

900

620

IPCC Bern Low

Bern High

HadleycoupledGCMppm


-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

1 2 3 4 5

CLIMATE FORCING (to 2000)

GHG

indirectaerosol

FForg C

FFblack Csulphate

direct

Source: IPCC TAR


WINTER ENGLAND & WALES PRECIPITATIONobserved to 1999; predicted to 2050

Ch

ang

ere

lati

veto

61-9

0av

erag

e(m

m)


CHANGE IN DJF PRECIPITATION (%)2080s - present, SRES A2, 3-member initial condition

ensemble


GLOBAL PRECIPITATION CHANGEdue to A2 emissions, predicted by 9 climate models

Source: IPCC, 2001

±70%


Ch

ang

ein

glo

bal

pre

cip

itat

ion

(mm

/day

)CHANGE IN GLOBAL PRECIPITATION

HadCM3 under a range of emissions scenarios

±25%


% CHANGE INWINTER

PRECIPITATION

2080s, A2


SEA LEVEL RISE REGIONALVARIATIONS

due to thermal expansion and ocean circulation changes only

0 0.1 0.2 0.3 0.4 0.5 0.6 mSource:

IPCC


CLOUDS AND CLIMATE

Low clouds reflect sunlight but traplittle infra-red radiation;

They act to cool climate

High clouds reflect sunlight but alsotrap infra-red radiation;

They act to warm climate

Global warming may change the characteristics of clouds,and thus alter their current net cooling effect; this could

exert a powerful feedback on climate change.

GJJ1999


PROBABILISTIC CLIMATEPREDICTIONS

Pro

bab

ility

Pro

bab

ility

100%

current position future position

2050s Paris summer rainfall-40% -30% -20% -10% 0%



PROBABILITY PREDICTIONS• Generate X (50 - 1000) climate models by varying

parametrisations within plausible limits

• Make simulation (1900-2100) with each model

• Assess credibility of each model based on currentclimatology and 1900-2000 simulation

• Weight prediction (2000-2100) according to modelcredibility

• Use X runs to generate pdf of a specific change

• pdf can be used direct in risk analyses

• next: do this with other climate models


PROBABILISTIC CLIMATEPREDICTIONS

ATMOSPHERE +CLOUDS

LAND ANDVEGETATION

CARBON CYCLE

OCEANCIRCULATION

ETC.

X CLIMATE MODELS

Pro

bab

ility



RESOLUTION OF CLIMATESCENARIOS

1998: GLOBAL MODEL 2002: REGIONAL MODEL

300km grid 50km grid


SIMULATION OF A TROPICAL CYCLONEin the PRECIS regional climate modelGlobal climate model Regional climate model

Met Office/Hadley Centre


REGIONAL MODEL PREDICTIONSOF CHANGE IN WINTER PRECIP BY

2080s

Rossby RCM Hadley RCM

Both RCMs driven byHadley Centre HadCM3 GCM


EMISSIONS AND CONCENTRATIONS OF CO2from unmitigated and stabilising emission scenarios

Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation

10

5

0

15

20

An

thro

po

gen

icC

O 2em

issi

on

s(G

tC/y

r)

2000 2050 2100 2150 2200 2250 2300 2350

CO

con

cen

trat

ion

(pp

m)

2

1000

950

900

850

800

750

700

650

600

550

500

450

400

3502000 2050 2100 2150 2200 2250 2300 2350

Source: IPCC


GLOBAL AVERAGE TEMPERATURERISE

from unmitigated and stabilising emission scenarios

1900 2000 2100 2200

0

2

4

Glo

bal

tem

per

atu

rech

ang

e(°

C)

3

1

Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation

Met Office/Hadley Centre


CROP YIELDchanges from the present day to the 2080s

Unmitigated emissions

Stabilisation of CO2 at 750 ppm Stabilisation of CO2 at 550 ppm

Potential change incereal yields (%)

10 – 5

0 – -2.5

-5 – -10-2.5 – -5

-10 – -20

2.5 – 05 – 2.5

No data

University of East Anglia/ IIASA Austria /Universidad Politecnica de Madrid/Goddard Institute for Space Studies

HadCM2


ANNUAL NUMBER OF PEOPLEFLOODED

with no climate change and under three emissionsscenarios

100

80

60

40

20

0

Peo

ple

flo

od

ed(m

illio

ns/

year

)

2020s 2050s 2080s

Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation No climate change

University of Middlesex

HadCM2


CHANGES IN STORED CARBON 1860-2100

– 10 –5 – 4 –3 –2 – 1 1 2 3 4 5 10

Change in carbon content (kg C per square metre)

Soilcarbon

Vegetationcarbon

Hadley Centrecoupled climatecarbon-cycle model


1000

800

600

400

200

with carbon cyclewithout carbon cycle

1900 1950 2000 2050 2100

CO

2co

nce

ntr

atio

ns

(pp

mv)

Met Office / Hadley Centre

EFFECT ON CO2 CONCENTRATIONOF CARBON CYCLE FEEDBACK


EFFECT ON LANDTEMPERATURES OF CARBON

CYCLE FEEDBACKwith carbon cyclewithout carbon cycle

1850–2

0

2

4

6

8

1900 1950 2000 2050 2100

Tem

per

atu

reri

se(°

C)

Met Office / Hadley Centre


Impact of carbon cycle feedbacks onCO2 concentrations (WRE550)


Cumulative emissions consistent withWRE550 CO2 concentration scenario


Impact of carbon cycle feedbacks onstabilisation level


SUMMARY: HANDLING UNCERTAINTIESIN CLIMATE CHANGE PREDICTIONS

• Emissions uncertainty– first half C21: uncertainty small∴ ignore– beyond: “scope” using range of SRES scenarios

• Science uncertainty– larger than SRES emissions uncertainty– initially: use a range of climate model results

(“calibrated” using 1990-2000 simulations)– soon: probability predictions

• Natural variability– quantify via initial condition ensemble

uncertainties in climate change · pdf filehadley centre for climate prediction and research 1...

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