Robert Vautard

1. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
9 August 2021
#ClimateReport #IPCC #IPCCAtlas
SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
Event Attribution – A tribute to
Geert Jan van Oldenborgh
Robert Vautard, Bart van den Hurk and many friends
from science

2. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis

3. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
How did we get there?
Central questions:
How can we verify model projections of climate change patterns?
Is what we observe due to climate change?
Detection of
response patterns
Hasselmann, 1979
Applications to attribution
of observed mean changes
eg., Hegerl et al., 1996, Hasselmann
et al 1997
…
Single event attribution
Allen et al., 2003
Stott et al., 2004
And further studies
Multi-model/methods
event attribution
2012

4. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
Rapid event attribution
• Do it in near real-time
• To have more reach
• Peer-review related
questions (many collective
discussions)
• Trigger conditions
• Bring together experts
• Define the event
• Collect observations and
available models
• Detection: observation
analysis
• Model evaluation
• Attribution: model
analysis
• Hazard Synthesis
• Vulnerability and
exposure
With F. Otto and several colleagues

5. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
Papers cited in Ch11

6. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
Climate Explorer https//climexp.knmi.nl
First IPCC Atlas
Integrator of data and
methods to be able to
share what he learnt over
the years

7. SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis
Climate Explorer
Geert Jan’s work on Climate Explorer:
• Started as “private project” in his home study
• To allow low-bandwidth areas (developing world) to
access crucial climate data
• Supporting monthly climate outlooks
• Growing to many Tb’s of data and >100000 users
per year
• Embedding in KNMI digital infrastructure was first a
private enterprise as well (estimating necessary
investments in weeks rather than years)
• Now part of main infrastructure and cloud based

8. Beyond, personal and collected
thoughts on GJvO
• A deep understanding of data
• An activist for open science & data, making it happen
• A way of making discussions so inspiring – one could not
have a discussion with him without a couple of new
papers in mind at the end…
• A sense of the essential, the right thing to do

9. Van Oldenborgh is not concerned
about his disease, but is
concerned about climate. “I won’t
know how this will end up”
Trouw, Jan 2020

10. Good bye Geert Jan we will
never forget you
Science will build upon what
you did, exactly as you always
wanted it