WG1 Co-Chairs vision

1. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
Challenges for WG1
WG1 Co-Chairs vision
Robert Vautard, senior
CNRS scientist
Institut Pierre-Simon Laplace
Xiaoye Zhang, Member
of Chinese Academy of
Engineering (CAE)

2. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
What can AR7 WG1 do after such a comprehensive AR6?

3. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
1. Vision = crossing between what the
community plans and what the governments
need
2. - More integration across WGs
3. - Solutions-oriented products
4. - More packed and focused reports
5. - Less workload for authors and TSUs
From lessons learned , knowledge gaps and Kigali WCRP

4. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
Since AR6, many, many more extremes and impacts
Philip et al., 2022
Maximum yearly temperature British
Columbia
Humid heat : 4-day average
daily maximum Heat Index
during April, 2023, WWA, 2023

5. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
Extremes in line with AR6 ; but lots of new information
For mitigation:
“[…] By the end of the century,
scenarios with very low and low
GHG emissions would strongly
limit the change of several CIDs,
such as the increases in the
frequency of extreme sea level
events, heavy precipitation and
pluvial flooding, and exceedance
of dangerous heat thresholds,
while limiting the number of
regions where such
exceedances occur, relative to
higher GHG emissions scenarios
(high confidence). […]”
WG1 SPM, D2.4

6. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
- Fate of carbon sinks due to land
degradation and climate change, and
related consequences on the remaining
carbon budget, CH4 emissions from
wetlands [remaining carbon budgets]
- Managed water cycle in a changing
climate, links between resource, use and
climate [water management & adaptation]
- Overshoot CMIP scenarios, and
CDR/Climate intervention
Knowledge gaps and emerging topics (examples)
• 2. Complex topics with policy relevance

7. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
- - Explain recent record-shattering,
compound regional events, global
events
- - Better identify critical regional
thresholds & global warming levels
for tipping points, or climate drivers
of ecosystems or social systems
tipping points
- - Explain regional model /
observations differences in trends
and variability
- - Regional information to impacts
Mechanisms and Impacts of Earth System
Tipping elements, Wang et al., 2023
Knowledge gaps and emerging topics expectations
• 1. Global AND regional information for mitigation and adaptation policies

8. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
Interfaces and discussion points (from WG1)
REGIONAL
CLIMATE
INFORMATION
ATLAS
CMIP
SCENARIOS
& WARMING
LEVELS
CARBON
WATER
WG3 WG2
WG1

9. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
Emulator
Warming levels
WG1 ESM
WCRP-CIMP
New Scenarios
Scientific Links
With WGs
WG1 WG2 WG3
Wait WG1
CIMP7 then
Hope WG3-WCRP
New Scenarios
calibrate
GST
Wait WG1
Altas
2028
A shorter and more focused AR report
will increase policy relevance and
readability and give less work to
authors
A synchronization of WG1 with other
WGs would better serve the needs for
adaptation and mitigation assessment;
WG1 could even start after WG3
(accommodating WG2/3 requests to
the WG1 assessment)
Even synthesis report should start first with scoping, or at
least three working groups scoping together
IPCC
AR?
IPCC
SR?

10. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
• - Inclusion of gray literature and consider indigenous knowledge
• - Enhanced inclusivity
• - Including practitioners in scoping activities
• - Carbon footprint
• - Use of AI
Other considerations

11. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
• “The choice and actions decided in this decade will
have impacts now and for thousands of years (high
confidence)” AR6 SYR, SPM, C.1
 It is key to bring relevant information along the cycle
 Consider diversified products
Timeliness of information

12. SEVENTH ASSESSMENT CYCLE
Working Group I – The Physical Science Basis
Thank you for your attention