Presentation by Bart van den Hurk, Scientific Director at Deltares, at the Delft-FEWS User Days (Day 1), during Delft Software Days - Edition 2021. Monday, 8 November 2021.

1. The IPCC AR6
assessment:
What’s in it for FEWS?
Bart van den Hurk
Deltares & VU University
Amsterdam
Lead Author IPCC AR6
Trouw, 6 Oct 2021

2. The WG-1 report in numbers
Why a new report?
• Science has evolved
• (most papers are newby’s)
• Climate has evolved
• (we’ve seen a lot of events)
• Society has evolved
• (we have a Paris treaty now)
SIXTH ASSESSMENT REPORT
Working Group I – The Physical Science Basis

3. Extra slides
Some new features
Display of warming levels
Many projections plotted for 1.5, 2, 3 and 4 warming
AR6 Technical Summary Fig TS.5

4. Extra slides
Some new features
Display of warming levels
Many projections plotted for 1.5, 2, 3 and 4 warming
Discussion of low-likelihood (extreme) sea level
scenarios
Makes use of “calibrated” confidence language
Likely = 17 – 83% range
AR6 Technical Summary Box TS.4

5. Extra slides
Some new features
Display of warming levels
Many projections plotted for 1.5, 2, 3 and 4 warming
Discussion of low-likelihood (extreme) sea level
scenarios
Makes use of “calibrated” confidence language
Likely = 17 – 83% range
Regional and impact-oriented focus
Interactive Atlas
Many “Climatic Impact-drivers”
AR6 Interactive Atlas

6. Some IPCC high-level messages

7. Climate change is already affecting every inhabited
region on Earth, in multiple ways.
AR6 Summary for Policy Makers

8. Climate change is already affecting every inhabited
region on Earth, in multiple ways.
AR6 Summary for Policy Makers

9. Climate change is already affecting every inhabited
region on Earth, in multiple ways.
AR6 Summary for Policy Makers

10. Climate change is well on its way.
And every degree of warming counts
AR6 Summary for Policy Makers

11. Different types of Sea Level Rise scenarios
Technical Summary
Questions so far?
Medium confidence processes:
- Thermal expansion
- Ocean dynamics
- Ice caps and glaciers
- Land water & dams
- Vertical land motion
Low confidence processes:
- Dynamics at Greenland and
Antarctica (ice shelves,
calving)
Low likelihood storyline =
SSP5-8.5 Medium confidence
processes + Low confidence
evidence

12. Our regional activities
Regional information and the Interactive Atlas

13. Interactive Atlas
• Observations and model projections
• Global and regional
https://interactive-atlas.ipcc.ch/

14. Multiple hydrometeorological quantities
https://interactive-atlas.ipcc.ch/
Mean precipitation change @2 oC

15. Multiple hydrometeorological quantities
https://interactive-atlas.ipcc.ch/
Max 1day precipitation change @2 oC

16. Multiple hydrometeorological quantities
https://interactive-atlas.ipcc.ch/
Change in consecutive dry days @2 oC

17. Basic information on region-specific climate change
AR6
Interactive
Atlas
Temperature change
warmest day (C)
Precipitation change
wettest day (%)
7%/C
1:1
Number of consecutive
dry days (-)
Mean temperature change (C)

18. Also available for South Asia
Temperature change
warmest day (C)
Precipitation change
wettest day (%)
7%/C
1:1
Mean temperature change (C)
AR6
Interactive
Atlas
Number of consecutive
dry days (-)

19. Also available for South Asia
Temperature change
warmest day (C)
Precipitation change
wettest day (%)
7%/C
1:1
Mean temperature change (C)
AR6
Interactive
Atlas
Number of consecutive
dry days (-)
Also mask for major
river basins available
Annual mean temperature
Annual
mean
precipitation

20. Some IPCC high-level messages
Climate, climate change and the 2021 flooding event

21. Extraordinary event – at this location
Precipitation 13 juli Precipitation 14 juli
Near surface
Middle Atmosphere

22. Evaluation with GRADE
Sensitive to extremes
in the precipitation
database
No
comparable
values in
summer

23. Climate change attribution
• No trend in observed precipitation
prior to the july 2021 event
• Averaged over this domain: 24h sum
in summer ~1:400 event
• Historical climate change: increased
probability with factor 1.2 – 9
• Climate impact on circulation
unknown
https://www.worldweatherattribution.org/heavy-rainfall-which-led-to-
severe-flooding-in-western-europe-made-more-likely-by-climate-change/

24. Some IPCC high-level messages
What’s in it for FEWS?
What’s in it for FEWS?

25. The hydrological research agenda
The future is becoming unpredictable
Extremes intensify, freak events become normal,
seasons on the run.
Forecasting essential for
preparedness
Forecasting systems need
continuous calibration

26. The hydrological research agenda
The future is becoming unpredictable
Extremes intensify, freak events become normal,
seasons on the run.
Weather and climate are strongly connected
Setting events central in the analysis
Scenarios of (future) weather
events are highly risk-
informative

27. The hydrological research agenda
The future is becoming unpredictable
Extremes intensify, freak events become normal,
seasons on the run.
Weather and climate are strongly connected
Setting events central in the analysis
We need to
Integrate the multiple drivers, impacts and options of
the earth system
Advanced digital twins and
earth system models for
climate impact assessment

28. More information
• 7 take-aways Deltares:
https://www.deltares.nl/en/news/seven-take-aways-
from-the-ipcc-wg-i-report-on-global-climate-change/
• Regional Factsheets:
https://www.ipcc.ch/report/ar6/wg1/#Regional
• Interactive Atlas:
https://interactive-atlas.ipcc.ch/
• Bart.vandenHurk@deltares.nl