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The IPCC 5th Assessment Reportprocess and findings
Francis ZwiersPacific Climate Impacts ConsortiumUniversity of Victoria, Victoria, BC, Canada
IOGP/JCOMM/WCRP WorkshopOur Future Climate – Understanding the spread of physical risk for the oil and gas industry25-27 September 2018, BP Upstream Learning Centre, Sunbury Upon Thames, UK
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Outline
• Background
• IPCC process
• Calibrated assessment language
• Key findings of the IPCC AR5
• Event attribution – an emerging aspect of the science
• Conclusions
• Note – my focus will primarily be on WGI
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Background
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Background
• The IPCC was established in 1988
– Joint UNEP and WMO sponsorship
– Currently 195 member countries
• Major assessment reports
– 1990, 1995, 2001, 2007, 2013/2014, 2021/2022
• Assessments in three broad areas
– WG1 – The Physical Science Basis
– WG2 – Impacts, Adaptation and Vulnerability
– WG3 – Mitigation
• Plus a Synthesis Report, Special Reports and
Task Force on National GHG Inventories (TFI)
guidance documents
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IPCC organization and process• The Panel consists of 195 member countries
– It elects a Bureau (34 members), scopes and approves IPCC products
– Products includes a full assessment report spanning the three working
groups, a few special reports, technical reports, etc.
• Governments nominate scientists to be authors
– Bureau selects authors, oversees production of approved products
• For each working group report and the synthesis report, the panel
– approves the summary for policy makers (line-by-line), and
– accepts the final full report
• There are some additional IPCC bodies including the
– Task Force on National GHG Inventories (TFI), and
– Task Group on Data
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IPCC Bureau Structure (34 members)
Chair Hoesung Lee
IPCC Vice ChairsKo Barrett, USA; Thelma Krug, Brazil; Youba Sokona (Mali)
WG I Co-chairsValerie Masson-Delmotte, France
Panmao Zhai, China
Vice ChairsEdvin Aldrain, Indonesia
Fatima Driouech, Morroco
Greg Flato, Canada
Jan Fugleslvedt, Norway
Mohammad I. Tariq, Pakistan
Carolina Vera, Argentina
Noureddine Yassaa, Algeria
WG II Co-chairsHans-Otto Portner, Germany
Debra Roberts, South Africa
Vice ChairsAndreas Fischlin, Switzerland
Mark Howden, Australia
Carlos Mendez, Venezuela
Joy Jacqueline Pereira, Malaysia
Roberto Sanchez Rodrigues, Mexico
Sergey Semenov, Russian Federation
Pius Yanda, U.R. of Tanzania
Taha Zatari, Saudi Arabia
WG III Co-chairsJim Skea, United Kingdom
Priyadarshi R Shukla, India
Vice ChairsAmjad Abdulla, Maldives
Carlo Carraro, Italy
Diriba Korecha Dadi, Ethiopia
Nagmeldin G.E. Mahmoud, Sudan
Ramon Pichs-Madruga, Cuba
Andy Reisinger, New Zealand
Diana Urge-Vorsatz, Hungary
TFI Co-chairsKiyoto Tanabe, Japan
Eduardo Calvo Buendia, Peru
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The Fifth Assessment Report
• Scope determined in 2009
– a scoping meeting proposed a draft outline
– The Panel (i.e., the governments) debate, alter and approve the outline
• Authors and Review Editors were selected in 2010
– Governments nominate scientists (process varies by country)
– IPCC Bureau selects from nominations based on expertise required,
scientific track record of nominees, various balance considerations
– More than 830 scientists were selected (259 for WG1; 25% of nominations)
• AR6 process currently underway is similar
– Scoping meeting occurred 1-5 May 2017
– Scoping document approved week of 6 Sept 2017
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The Fifth Assessment Report• Main products
• Special Report on Renewable Energy (SRREN): 13 May 2011
• Special Report on Extremes (SREX): 17 Nov 2011
• WG1 (Physical Science Basis): 27 Sept 2013
• TFI guidance updates (Wetlands, Revised methods arising from the
Kyoto protocol): 18 Oct 2013
• WG2 (Impacts, Adaptation, Vulnerability): 30 March 2014
• WG3 (Mitigation): 12 April 2014
• Synthesis Report: 1 November 2014
• Approval/acceptance
– Line-by-line panel approval of the Summary for Policymakers
– Acceptance of the underlying report
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AR5 review process• Three stage review process
– Expert review of the 1st order draft
– Government and Expert review of the 2nd order draft
– Government review of the draft Summary for Policymakers
• Transparency
– Open to all experts (subject to registration and a declaration of expertise)
– Authors respond to all comments
– Review Editors oversee process and advise authors
– Comments and responses become part of the public record
• For WG1
– 54677 comments
– 1089 expert reviewers from 55 countries and 38 governments
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Authors are asked to produce an assessment
• Assessment of new climate models and simulations
– Includes new analyses of climate change simulations that are made
available by a cut-off data (e.g., CMIP6) using established methods
• Assessment of the literature as it exists at a specified cutoff date
– 30 Sept 2020 for WG1 AR6
– the approval session is scheduled for 12-16 April 2021
• Review process is critical
– Informs authors of recent studies they might have missed
– Provided constructive challenges of their interpretations and assessments
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IPCC calibrated language
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IPCC calibrated language
• Key assessments are made using calibrated language
• Has evolved over several assessments, with the latest update in
2010 as part of the AR5 process
• Current guidance integrates historical practices in the three WGs
– WG1 – likelihood assessments (exceptionally unlikely to virtually certain)
– WG2 – confidence assessments (very low, low, medium, high, very high)
– WG3 – evidence/agreement assessments (3 levels each indicating the
amount of evidence and the level of agreement)
• Evidence/agreement → confidence → likelihood
• Likelihood assessments are quantified as percent probability
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Examples of key WG1 assessments
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Warming of the climate system
is unequivocal, and since the
1950s, many of the observed
changes are unprecedented
over decades to millennia. The
atmosphere and ocean have
warmed, the amounts of snow
and ice have diminished, sea
level has risen, and the
concentrations of greenhouse
gases have increasedIPCC AR5 WG1 Figure SPM.1
Some assessments are stated as facts
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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).
Examples of the use of confidence and likelihood language
IPCC AR5 WG1 Figure SPM.3cIt is virtually certain that the
upper ocean (0−700 m) warmed
from 1971 to 2010
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Confidence in precipitation change averaged over global land areas since 1901 is
low prior to 1951 and medium afterwards. Averaged over the mid-latitude land
areas of the Northern Hemisphere, precipitation has increased since 1901 (medium
confidence before and high confidence after 1951). For other latitudes area-
averaged long-term positive or negative trends have low confidence.
Examples of complex and carefully nuanced assessments
IPC
C A
R5 W
G1 F
igure
SP
M.2
mm yr-1 per decade
Observed
change in
annual
precipitation
over land
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Human influence has been
detected in warming of the
atmosphere and the ocean, in
changes in the global water cycle,
in reductions in snow and ice, in
global mean sea level rise, and in
changes in some climate extremes
…. It is extremely likely that human
influence has been the dominant
cause of the observed warming
since the mid-20th century.
Example of strong likelihood
language on the causes of
observed changes
IPC
C A
R5 W
G1 F
igure
SP
M.6
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Global surface temperature change for the end of the 21st century is likely to
exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is
likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed
2°C for RCP4.5 (medium confidence).
Example of an assessment of projected changes
IPC
C A
R5 W
G1 F
igure
SP
M.7
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Cumulative emissions of CO2
largely determine global
mean surface warming by
the late 21st century and
beyond. Most aspects of
climate change will persist
for many centuries even if
emissions of CO2 are
stopped. This represents a
substantial multi-century
climate change commitment
created by past, present and
future emissions of CO2.
Commitment and irreversibility
IPC
C A
R5 W
G1 F
igure
SP
M.1
0
Likely < 2º
(vs1861-1880)
1870-2011: 515 ± 70 GtC
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Key findings
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• Warming in theclimate system isunequivocal
• It is extremely likely that we are the dominant cause of warming since the mid-20th century
(IP
CC
20
13
, F
ig.
SP
M.1
b)
IPC
C A
R5 W
G1 F
igure
SP
M.1
b
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Additional indicators of the thermal status of the climate
IPC
C A
R5 W
G1 F
igure
SP
M.3
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The primary driver of the observed warming
IPC
C A
R5 W
G1 F
igure
SP
M.4
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Projected change depends on the future emissions pathway
IPC
C A
R5 W
G1 F
igure
SP
M.7
an
d S
PM
.9
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Surface air temperature and precipitation projections
IPC
C A
R5 W
G1 F
igure
SP
M.8
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Arctic sea ice extent and global sea level rise projections
RCP 2.6
RCP 8.5
Sea level riseArctic September sea ice extent
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IPCC AR5 Synthesis Report
Some of the changes in extremes observed since about 1950 have been linked to human
influence, impacts are occurring, projected changes further increase risks
AR5 WGI SPM
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IPCC AR5 Synthesis Report
SYR Synthesis:
There is a choice
Figure SPM.10,
WG3
Emissions
WG1
Climate
Response
WG2
Resultant
Risks
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IPCC AR5 Synthesis Report
Key Messages from the Synthesis Report
– Human influence on the climate system is clear
– The more we disrupt our climate, the more we
risk severe, pervasive and irreversible impacts
– We have the means to limit climate change and
build a more prosperous, sustainable future
AR5 WGI SPM, AR5 WGII SPM, AR5 WGIII SPM
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F
Photo credit
Event attribution
Fort McMurray evacuation, May, 2016
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The context …
• Media discourse tends to evoke links to climate change
• As a default, scientists point to the similarity between recent
events and projected change
• Event attribution science has been trying to find a way for
science to do better than this
• Requires “rapid response” science
– e.g., see annual BAMS report on extreme events
• Places high demands on process understanding, data,
models, and statistical methods
• Recently assessed by US National Academies of Science
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Event attribution
• The public asks:
– Did human influence on the climate system cause the event?
• Most studies ask
– Did it affect its odds of occurrence of an event at least as extreme as
observed or did it alter its likely magnitude?
• Odds or change in likely magnitude assessed by comparing
factual and “counterfactual” climates
– Counterfactual → the world that might have been
• Comparison is usually based on climate models, but can also be
data driven
• Shepherd (2016) defines this as “risk based”
– Contrasts it with a “storyline” based approach
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Confidence in c
apabili
ty f
or
event
att
ribution
Understanding of effect of climate change on event type
NAS assessment
34Edmonton Expo Centre at Northlands. Photo, Chris Bolin
Mandatory evacuation. Photo, Jason Franson/CPAvian escape. Photo, Mark Blinch/Reuters
Fort McMurray 2016 fire impacts
• 590,000 ha burnt
• 88,000 people displaced
• 2 fatalities (indirect)
• 2400 homes and 665 work
camp units destroyed
• $3.6 B CDN insured losses
Timberlea. Photo, Chris Bolin
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Fire risk (Kirchmeier-Young et al, 2017)• We asked whether human
induced climate change affected
fire risk in the“Southern Prairie”
Homogeneous Fire Regime zone
• Measure fire risk using “CWFIS”
system indicators
– Fire Weather Index
– Fine Fuels Moisture Code
– Duff Moisture Code
– Drought Code
Annual area burned 1981-2010
Canadian National Fire Database
Southern Prairie HFR Zone
• These indices depend on temperature, relative
humidity, wind speed, and precipitation
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Fire Weather Index for Southern Prairies HFR
for the current decade (2011-2020)
FWI
Pro
babili
ty d
ensity
NATALL
Figure S6: T he probabilit y of necessary causalit y (PN) for many event met rics. Values are for an event more ext reme than
that indicated on the horizontal axis and the vert ical bar represents the threshold for an ext reme value. T he uncertainty range
for each PN curve is shaded and was calculated using a bootst rapping method. T he FBP met r ics in panels (i) - (k) use the C2
fuel class.
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FWI
𝐹𝐴𝑅 =𝑝𝐴𝐿𝐿 − 𝑝𝑁𝐴𝑇
𝑝𝐴𝐿𝐿
pALL
pNAT
CWFIS “Extreme” FWI level = 30
Observed FWI level in Fort Mac area ≈ 40
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Conclusions
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Conclusions• IPCC Assessment Reports are very thoroughly reviewed
• The process allows “ownership” of the reports by the participating
members of the Panel (i.e., the governments)
• They reflect a strong scientific consensus on the state of
understanding of the climate system, the impacts of changes,
means for adaptation and potential for mitigation
• Findings indicate a very high level understanding of the thermal
response to anthropogenic forcing but lower levels of
understanding of the dynamic response
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Conclusions• Collectively, we are responsible for most of the warming over the
past century
• Continuing emissions will lead to more warming, faster long-term
sea level rise, further ocean acidification, further impacts on
extremes, etc.
• We can limit many risks by reducing emissions
• Limiting warming to a level such as 2°C will require ambitious
mitigation and possibly negative emissions
• The possibility of surprises (in the physical climate system and in
the social and ecological systems that are affected by, and feed
back upon, the climate system) exists, but the associated
likelihoods and risks are not yet well understood.
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Questions
https://www.pacificclimate.org/Ph
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