© Yann Arthus-Bertrand / Altitude

An Overview of the Fifth Assessment Report of the IPCC WG1

An Overview of the Fifth Assessment Report of the IPCC WG1

Masahide KimotoAtmosphere and Ocean Research Institute

The University of Tokyo LA, Ch 11, IPCC AR5 WG1

Key SPM Messages

19 Headlineson less than 2 Pages

22009: WGI Outline Approved

14 ChaptersAtlas of Regional Projections

54,677 Review Commentsby 1089 Experts

2010: 259 Authors Selected

Summary for Policymakers~14,000 Words

Limiting climate change will require substantial and sustained reductions of 

greenhouse gas emissions

Limiting climate change will require substantial and sustained reductions of 

greenhouse gas emissions

Warming in the climate systemis unequivocal

Warming in the climate systemis unequivocal

Human influence on theclimate system is clearHuman influence on theclimate system is clear

Key Findings

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

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

(IPCC 2013, Fig. SPM.1)

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

It is virtually certain that the upper ocean (0−700 m) warmed from 1971 to 2010, and it likely warmed between

the 1870s and 1971. It is likely that the ocean warmed between 700 and 2000 m from 1957 to 2009.

The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels

unprecedented in at least the last 800,000 years.(They) have all increased since 1750 due to human activity.

(IPC

C 2

013,

Fig

. SP

M.5

)

Total radiative forcing is positive, […]. The largest contribution to total radiative forcing is caused by the increase in the

atmospheric concentration of CO2 since 1750.

Human influence on the climate system is clear.

(IPC

C 2

013,

Fig

. SP

M.6

)

Human influence on the climate system is clear.

(IPC

C 2

013,

Fig

. SP

M.6

)

Representative Concentration Pathways (RCP)

RCP8.5

RCP6.0

RCP4.5

RCP2.6

Global surface temperature change for

the end of the 21st century is likely to

exceed 1.5 ⁰C relative to 1850 for all scenarios

except RCP2.6.

(IPCC 2013, Fig. SPM.7a, SPM.8a)

(IPCC 2013, Fig. SPM.7, SPM.8)

Changes in the global water cycle in response […] will not be uniform. The contrast in precipitation between wet

and dry regions and between wet and dry seasons will

increase […].

Global mean sea level will continue to rise during the 21st century

(IPC

C 2

013,

Fig

. SP

M.9

)

Changes in Extreme Weather and Climate Events

(IPCC 2013, Table SPM.1)

AR5SREXAR4

Regional Changes: Tropical Cyclones

(IPCC 2013, Fig. 14.17)

Projections and Emissions

(IPC

C 2

013,

Fig

. TS

.4)

Limiting climate change will require substantial and sustained

reductions of greenhouse gas emissions.

(IPCC 2013, Fig. SPM.10)

CumulativeEmission

SinkSourcedtdT

dtSinkSourcedtdtdT t

t

t

t 2

1

2

1

dtSinkSourceTt

t 2

1

dtSourcet

t2

1

∆T=2ºC

Future

∆T

Present

Future

CO

2 Em

issi

on

Present

hiatus 【hɑɪéɪṭəs】隙間, 裂け目, 間隙, 活動休止(類) an interruption in the intensity or amount of something

Recent pause in global warming:the "Hiatus" problem

←Obs.2001-2010

Hiatuspatternin GCM→

Watanabe et al. (2013)MOHC (2013)

CMIP5 decadal prediction

Global mean surface temperature anomaly time seriesBars: ObservationThick line: CMIP5 initialized hindcasts. Multimodel meanDashed line: CMIP5 non-initialized hindcasts. Multimodel mean

Doblas Reyes et al. (2013)

“hiatus”

Near-TermProjection

Fig. 11.25 IPCC AR5

© Yann Arthus-Bertrand / Altitude

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