Future Role of IPCC
Yoichi Kaya
Chairman, Japanese Liaison Committeefor IPCC
２０１７．１．２６1

Contents
1.Basic Character of IPCC
policy relevant vs.prescriptive
2.Examples
1) Skepticism on global warming2) Evaluation of feasibility of response measures3) Climate sensitivity
3. Concluding Remarks

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Basic character of IPCC
1．Gathering of scientists supported by governments→ the duty of co-operation for policy making→ the duty of gathering the most recent scientificinformation
2. Basic stance of IPC
policy relevant but not policy prescriptive
3. Key issues
To what extent do we provide with useful
informations?
The followings are three examples.
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Skepticism on global warming
１．Those who are skeptic about global warmingex.1 ratio of those who are skeptic about GW in USA
40% or around ( public review )ex.2 US government１）President Trump
２）Considerable number of republicans in the diet
２．Extence of several scientific skepticism
Ex.：H.Svensmark
Solar irradiance→magnetic field around sun→total flux of cosmic ray on the earth→total clounds on the earth surface→earth surface temperature

4Treatment of skepticism in thepast IPCC reports (1)１．General
source:WG1 SPM p.17
It is extremely likely that human influence(95 – 100% )has been the dominant cause of the observed
warming since the mid-20th century.

5Treatment of skepticism in the past IPCCreportsー(2) the case of Svensmarkー１．Solar irradiance ー Global temp. change
1)source:IPCC AR5 WG1 SPM p.19
Not correlated in the data between 1986-2008
2) source:IPCC AR5 WG1 Box.10.2 p885
Almost the same as above
２．Cosmic ray ー cloud coversource: IPCC AR5 WG1 chap.7, p.613
Not correlated
6Request to IPCC on the skepticism
about global warming
１．Introduce real examples of skepticism
２．Show clear evidence for rejecting skepticism
Example：Svensmark’s skepticism
１）Clear explanation of his skepticism
２）Clear explanation of the evidence
ex.：results of statistical analysis on therelation of solar irradiance and earth
surface temperature

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About future emission pathways
１．Past example
RCP2.6～8.5 → emission pathways
2. AR6: 2degree and 1.5 degree targetpathways
and mitigation measures, particularly
new ones such as negative emissions

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RCP:Representative Concentration Pathways（number: 2100 Radiative forcing (W/m2) )9

Source:Rogelj,J.et al:Nature c.c. vol.5.June 2015

GlobalCO2emission(Gt/y)

2℃target case

1.5℃ target case10

Difficulty in anthropogenic
CO2 absorption＜Main measures for CO2 absorption＞
1. Afforestation and Reforestation
CO2 absorption per year: 9ton/ha
２．BECCS（biomass burning＋CCS）
CO2 absorption of grass fields about 5ton/ha
３．DAC ( Chemical absorption of CO2 in the air )＜Area neccesary for 1 / 2 ＞
10Gt/y CO2 → 1Gha or greater＞total area of USA
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CO2 emission in Japan in 2013

Power generation

CO2Iron & steel
cementtransportation
鉄鋼セメント
運輸
民生
他非電力
電力
Residential/commercialother。

Non Electric

12Structure of power generation- Japan, 2030Fossil fuels

nuclear

原子力水力等
太陽光風力火力
hydroSolar and wind power

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ECS in IPCC report(Equibrium Climate Sensitivity)
estimate

best estimate

AR1～3AR3

1.5～4.5℃

2.5℃

AR4

2.0～4.5℃

3.0℃

AR5

1.5～4.5℃

no concensus

14Structure of main models in IPCCGHG
Economic activities

GHG emission

Temp. estimate（MAGICC)

Air
Temp.

ECS probability
func.
（+best estimate）
IPCC WG1

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GHGemission(Mt CO2/y)
80000

GHG排出量（MtCO2eq./yr）

70000

60000

50000

40000

30000

20000

10000

現状政策継続Extrapolation of past trends

INDC
2020年以降の約束草案高位削減

INDC

2100年2.0℃_気候感度3.0℃(530 ppmを一旦超える)
2deg.target / ECS=3.0deg
2100年2.0℃_気候感度2.5℃(580 ppmを一旦超える)
2deg. target /ECS=2.5deg

01990

2000

2010

2020

2030

Fig. Impact of ECS value on emission paths

2040

2050
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Concluding remarks
1. IPCC should deliver as clear informations as
possible on climate change, including results offeasibility evaluation of major response measures.
These efforts will greatly increase values ofinformations provided by IPCC, butthese are not contradictory to the IPCC spirit of“policy relevant but not prescriptive”.
2. IPCC should utmost efforts for reducing
uncertainties of important parameters of climatechange such as climate sensitivity.
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