CLIMATE CHANGE - An introduction · Hadley Centre for Climate Prediction and Research CLIMATE...

Hadley Centre for Climate Prediction and Research

CLIMATE CHANGEAn introduction

Geoff Jenkins, Hadley Centre, Met Office, Exeter, UK

• Introduction: the greenhouse effect and climate modelling

• How has climate changed, and is Man responsible?

• How will climate & sea level change in the future?

• Certainties, uncertainties and probabilities

UNFCCC Climate Kiosk at CoP9, 11 December 2003


SUN

Sunlightpasses

through the atmosphere..

..and warms the earth.

..most escapes to outer spaceand cools the earth...

Infra-red radiationis given off by the earth...

…but some IR is trapped by some gases in the air,

thus reducing the cooling.

THE GREENHOUSE EFFECT


HOW QUICKLY THE CLIMATE WILL CHANGE IN FUTURE DEPENDS ON:

• How much greenhouse gas emissions grow

–this depends on population growth, energy use, new technologies, etc

• How sensitive the climate system is to emissions

–how clouds, ice, oceans etc respond to the extra heating; we build a mathematical model of the earth’s climate system to calculate this


PREDICTING CLIMATE CHANGE

CONCENTRATIONSCO2, methane, etc.

HEATING EFFECT‘Climate Forcing’.

IMPACTSFlooding, food supply, etc.

Scenarios frompopulation, energy,economics models

Carbon cycle andchemistry models

Gas properties

Coupled climatemodels

Impacts models

CLIMATE CHANGETemp, rain, sea-level, etc.

EMISSIONS

GJJ1999

feed

back

s


THE CLIMATE SYSTEM

OCEAN

PrecipitationSea-ice

LAND

Ice- sheetssnow

Biomass

Clouds

Solarradiation

Terrestrialradiation

Greenhouse gases and aerosol

ATMOSPHERE

GJJ1999


GLOBAL SURFACE TEMPERATURES 1861-2002

2003 to September in green

1.0°F

1.5°F


GLOBAL SURFACE TEMPERATURES OVER LAND 1861-2002

2003 to September in green

1.0°F

2.0°F


TROPOSPHERICAND

STRATOSPHERICTEMPERATURES

1958-2002Tem

per

atu

re c

han

ge,

°C

Tem

per

atu

re c

han

ge,

°C


Possible causes of recent climate change

• Natural internal climate variability (“chaos”)

• Natural factors that force change

– orbit of the earth around the sun

– energy output of the sun

– volcanic particles in the stratosphere (“dust”)

• Man-made factors that force change

– greenhouse gases (CO2, methane….)

– small particles (cooling effect of sulphates, etc)


OBSERVED AND SIMULATED CHANGEcalculated using only natural factors

Tem

per

atu

re c

han

ge

ºC 1.0

0.5

0.0

-0.51850 1900 1950 2000

observedmodel simulation


MAN-MADE CO2 EMISSIONS


Carbon Dioxide in the Atmospherehas risen by over 30% due to human activities


Observed and simulated climate changefrom natural AND Man-made factors

Tem

per

atu

re c

han

ge

ºC 1.0

0.5

0.0

-0.51850 1900 1950 2000

observedmodel simulation


MAN-MADE CO2 EMISSIONS (Gt/yr)IN THE IPCC SRES SCENARIOS


GLOBAL TEMPERATURE RISEfrom 5 IPCC SRES emissions scenarios

4°F

9°F


GLOBAL TEMPERATURE RISE OVER LANDfrom 5 IPCC SRES emissions scenarios

Tem

per

atu

re r

ise,

deg

rees

C

A1FI emissionsA2A1BB2B1

12°F

6°F


N HEMISPHERE TEMPERATURE 1000 - 2100

Proxy-observations Weather stationsPredictions (high emissions)Predictions (low emissions)

Tem

per

atu

re r

ise

(deg

rees

C)


PATTERN OF ANNUAL TEMPERATURE CHANGES2080s relative to present day

High emissions scenario

0 1 2 3 4 5 6


–3 –2 –1 1 2 3–0.5 0.5–0.25 0.250

High emissions scenario

PATTERN OF ANNUAL PRECIPITATION CHANGES2080s relative to present day

mm/day


Extent of arctic summer sea-ice

High emissions


GLOBAL SEA LEVEL RISE0.5

0.4

0.3

0.2

0.1

Sea

-lev

el r

ise

(m)

1990 2000 2020 2040 2060 2080 2100

Thermal expansion+ glacier melt+ Greenland+ Antarctica(land movement

not included)

A1FIA2B1B2

HadCM3


GLOBAL SEA LEVEL RISEfrom all emissions and models

Highest emissions scenarioMost extreme climate model

Lowest emissions scenarioLeast extreme climate model

90cm

10cm


SEA LEVEL RISE COMMITTMENTH

adCM

2 GH

G

00 50 100 150 200 250 300 350 400 450 500 550 600

Sea

-lev

el r

ise

(m)

0.2

0.4

0.6

0.8

ClimateChange

No climatechange

years


UN Framework Convention on Climate Change

• “The ultimate objective of this Convention is…stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous interference with the climate system…”

• Research currently underway to decide what concentration constitutes a “dangerous level”

• Negotiations would then have to agree the common but differentiated contributions to achieving this stabilisation level, and by when.


EMISSIONS AND CONCENTRATIONS OF CO2from unmitigated emissions and possible emission pathways to stabilisation at 550ppm and 750ppm

Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation

10

5

0

15

20

An

thro

po

gen

ic C

O 2em

issi

on

s (G

tC/y

r)

2000 2050 2100 2150 2200 2250 2300 2350

CO

co

nce

ntr

atio

n (

pp

m)

2

1000

950

900

850

800

750

700

650

600

550

500

450

400

3502000 2050 2100 2150 2200 2250 2300 2350


GLOBAL AVERAGE TEMPERATURE RISE from unmitigated and stabilising emission scenarios

1900 2000 2100 2200

0

2

4G

lob

al t

emp

erat

ure

ch

ang

e (°

C)

3

1



AREA OF VEGETATION DIEBACK5

1

2

3

4

02000 21002050 2150 2200 2250

Are

a o

f ve

get

atio

n d

ieb

ack

(mill

ion

km

2 )


WithCEH

Edinburgh


ANNUAL NUMBER OF PEOPLE FLOODEDwith no climate change and under three emissions scenarios

100

80

60

40

20

0

Peo

ple

flo

od

ed (

mill

ion

s/ye

ar)

2020s 2050s 2080s

Unmitigated emissions 750 ppm stabilisation 550 ppm stabilisation No climate change

WithUniv

Middlesex


Certainties, uncertainties, probabilities• The natural greenhouse effect already warms us by 30°C

• Man’s activities increased CO2 & other greenhouse gases

• More greenhouse gases will warm us further

• The earth has warmed by about 0.7°C over last 100y

• Most of the last 50y warming is likely due to Man’s activities

• Global warming by 2100 is projected to be 1.4 – 5.8°C

• Uncertainties at local scale are greater

• Probabilistic predictions will replace the current range of deterministic predictions


SUMMER TEMPERATURE

RISE OVER ITALY

by 2080s due to SRES A2 emissions

PREDICTEDBY NINECLIMATEMODELS

0 1 2 3 4 5 6 7°C


PROBABILITY OF CHANGE IN

SUMMER DAILY MAXIMUM

TEMPERATUREIN MILAN

by the 2080s under SRES A2

Change in summer Tmax, °CDave Sexton53-memberHadSM3


SUMMARY

• Warming of 1°C over land since C19; 2002 ranked #3

• Likely that most of the recent warming is Man-made

• Predictions of global warming 1.4 – 5.8°C by 2100

• Uncertainty mainly due to understanding & modelling

• Probabilistic predictions are required for adaptation;

work in hand

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