Thomas StockerClimate and Environmental Physics, University of Bern

14th International Seminar on Climate System and Climate Change, Zhuhai

IPCC AR5: The Physical Science Basis (1)Lecture 3:

Lecture 3:IPCC AR5: The Physical Science Basis (Part 1)

1. Challenges of a comprehensive assessment

2. Observed climate change

3. Understanding man-made climate change

14th International Seminar on Climate System and Climate Change, Zhuhai

Structure of the Intergovernmental Panel on Climate Change

No IPCC assessment without a strong team of Co-Chairs

Principles Governing IPCC Work (1998, 2003, 2006, 2011)

[...]

[...]

19901995

2001

2007

2013

IPCC Assessment Reports since 1990: WGI Contribution

Science Community Governments

Scoping of Outline of the Fifth Assessment Report

Approval of Outline

Nomination and Selection of Experts

0-Order Draft (ZOD)Informal Review

1-Order Draft (FOD)Expert Review

Government Review2-Order Draft (SOD)Expert Review

Final Draft Government Review

Approval of SPM and Acceptance of Report

Lead Authors of Working Group

2011

2010

2012

2013

Election of WG Bureau2009

2008

Sept2013

IPCC Process (WGI):

1

2

3

4

Expert MeetingGHG MetricsMarch 2009Expert Meeting

D&ASeptember 2009

Expert MeetingMulti Model Evaluation

January 2010

WorkshopSea Level Rise &

Ice Sheet InstabilitiesJune 2010

Cross-WG MeetingUncertaintiesJuly 2010Expert Meeting

Ocean Acidification Impacts

January 2011

Expert MeetingGeoengineering

June 2011

Other Working Group I Activities in Support of AR5

Special ReportManaging Risks of Extremes

2009-2011

Facts About the WGI Contribution to IPCC AR5

v 209 Lead Authors and 50 Review Editors from 39 countries

v Over 600 Contributing Authors

v More than 2 million gigabytes of numerical data from climate models

v Over 9200 scientific publications cited

v 1089 expert reviewers from 55 countries and 38 governments

v 54,677 review comments

v Panel, consisting of 195 member countries, approved SPM and accepted report

Key SPM Messages

19 Headlineson less than 2 Pages

10

14 Chapters & Atlas

1,100,000 Words

Summary for Policymakers

14,000 Words

11

Observations

Understanding

Future

www.climatechange2013.org

Lecture 3:IPCC AR5: The Physical Science Basis (Part 1)

1. Challenges of a comprehensive assessment

2. Observed climate change

3. Understanding man-made climate change

14th International Seminar on Climate System and Climate Change, Zhuhai

Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.

IPC

C 2

013,

Fig

. SPM

.1a

Anom

aly

(°C

) rel

ativ

e to

196

1-19

90

© IP

CC

201

3

In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years (medium confidence).

IPCC 2013, Fig. 5.7

Warming of the climate systemis unequivocal

IPC

C 2

013,

Fig

. SPM

.1b

Temperature Difference 1901 to 2012 based on trend (°C)

Averaged over the mid-latitude land areas of the Northern Hemisphere, precipitation has

increased since 1951 (high confidence).

IPC

C 2

013,

Fig

. SPM

.2

Precipitation Difference 1951 to 2012 based on trend (mm/yr per decade)

IPC

C 2

013

Fig.

TS.

3

Ice loss from Glaciers 226 (±60%) Gt yr-1 (1993-2009)

Greenland 215 (±25%) Gt yr-1 (2002-2011)

Antarctica 147 (±50%) Gt yr-1 (2002-2011)

© IPCC 2013

100 Gt yr-1 of ice loss corresponds to 0.28 mm yr-1 of global mean sea level rise

IPCC 2013 Fig. 3.1

It is virtually certain that the upper ocean (0-700 m) warmed from 1971 to 2010, [...]. It is likely that the ocean

warmed between 700 and 2000 m from 1957 to 2009.

Change in upper ocean temperature (°C)

Ener

gy (1

021 J

oule

s)

Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 (high confidence).

IPCC 2013, Box 3.1, Fig. 1

IPC

C 2

013,

Fig

. SPM

.3

It is virtually certain that the upper ocean (0-700 m) warmed from 1971 to 2010, [...]. It is likely that the ocean

warmed between 700 and 2000 m from 1957 to 2009.

Over the period 1901 to 2010, global mean sea level rose by 190 mm.

IPC

C 2

013,

Fig

. SPM

.3d

Glo

bal m

ean

sea

leve

l (m

m)

The concentrations of CO2, CH4 und N2O have all increased since 1750 due to human activity.

CO2: +40%

CH4: +150%

N2O: +20%

IPC

C 2

013,

Fig

. 6.1

1

Year 0 − 1750

IPC

C 2

013,

Fig

. TS.

4

CO

2 Em

issi

ons

(Bill

tons

C /

yr)

Increased use of coal has reversed the trend of gradual decarbonization of the world’s energy supply

( mod

ified

from

Pet

ers

et a

l., 2

013,

Glo

bal C

arbo

n Pr

ojec

t)

20139.9±0.5 Bill tons C per year

+61%since Rio '92

CO

2 Em

issi

ons

(Bill

tons

C /

yr)

CO2 emissions by human activity are unprecedented

Lecture 3:IPCC AR5: The Physical Science Basis (Part 1)

1. Challenges of a comprehensive assessment

2. Observed climate change

3. Understanding man-made climate change

14th International Seminar on Climate System and Climate Change, Zhuhai

IPC

C 2

013,

Fig

. SPM

.5

CO2 provideslargest RF

Total radiative forcing is positive, and has led to an uptake of energy in the climate system. The largest contribution [...] is caused by the increase in the atmospheric concentration of CO2 since 1750.

IPC

C 2

013

Fig.

SPM

.5

It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th

century.

IPC

C 2

013,

Fig

. TS.

9

including CO2 excluding CO2

Models reproduce observed continental-scale surface temperature patterns and trends over many decades

IPC

C 2

013,

Fig

. TS.

9

1998

IPC

C 2

013,

Fig

. TS.

9

Decadal temperature trends in climate models

Haw

kins

et a

l., 2

014

Decadal temperature trends in climate models

Haw

kins

et a

l., 2

014

Decadal temperature trends in climate models

Haw

kins

et a

l., 2

014

Decadal temperature trends in climate models

Haw

kins

et a

l., 2

014

Northern Hemisphere

Southern Hemisphere

NAS

A G

ISS

Surfa

ce T

empe

ratu

re A

naly

sis

2017

2014

20152016

Annual Mean Temperature Change°C

rela

tive

to 1

951

- 198

0

It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th

century.

IPC

C 2

013,

Fig

. TS.

9

including CO2 excluding CO2

atmosphere, land, ocean

extreme events

water cycle

global mean sea level

Human influence on the climate system is clear.

sea ice, glaciers, ice sheets

CauseWorldwide Effects

Lecture 3: Take-home messages

• IPCC provides a comprehensive, robust, and transparent assessment of anthropogenic climate change.

• Calibrated uncertainty language enables a clear communication which remains faithful to the scientific findings.

• Warming of the climate system is unequivocal and since the 1950s, many of the observed changes are unprecedented over decades to millennia.

• Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.

www.climatechange2013.org