Dr. Junguo Liu's presentation on water for the WRI IPCC report webinar session 2.

1. SIXTH ASSESSMENT REPORT
Water and Climate Change
[Credit: Toomas Tartes]
Working Group II –Impacts, Adaption and Vulnerability
The Sixth Assessment Report of IPCC
Junguo Liu
Southern University of Science and Technology,
Shenzhen, China

2. Sixth Assessment Report (AR6) of IPCC
• The Working Group I contribution was
released on 9 August 2021.
• The Working Group II contribution
was released on 28 February 2022.
• The Working Group III contribution will
be released in early April 2022.
• The Synthesis Report will be the last of
the AR6 products and is scheduled to be
released in September 2022.

3. Working Group II contribution
• 18 Chapters, 7 Cross-Chapter Papers,
and 2 Annexes
• 270 authors from 67 countries
• 34,000 + scientific papers
• 62,418 review comments

4. Chapter 4 Water
Farewell Meeting
March 16, 2022 (1.5 hours ago)
• 12 Coordinating Lead Authors/ Lead Authors
• 2 Review Editors

5. Chapter 4 assesses observed and projected
climate-induced changes in water cycle, their
current impacts and future risks on human and
natural systems and the benefits and effectiveness
of water-related adaptation efforts
4.2: observed changes in hydrological cycle
4.3: societal impacts of observed changes and
attribution to CC
4.4: projected risks of changes in hydrological cycle
4.5: projected sectoral risks
4.6 and 4.7: water-related adaptation responses
4.8: enabling principles for meeting water security,
SDGs and climate-resilient development.
Chapter 4: Water
Structure of Chapter 4

6. • Currently, ~4 billion people are
estimated to experience severe water
scarcity for at least one month per year
(medium confidence)
• Since the 1970s, 44% of all disaster
events have been flood-related
• ~60% adaptation interventions is
forged in response to water-related
hazards (high confidence)
The importance of water
Distribution of water scarcity
Global Water Security Index

7. Key Finding 1
Intensification of the hydrological cycle due to human-induced climate change is
affecting physical aspects of water security (high confidence), thereby exacerbating
existing water-related vulnerabilities caused by other socioeconomic factors

8. • There is a clear trend of increases in streamflow in the
northern higher latitudes (high confidence) !with climatic
factors being more important than direct human influence
• Nearly half a billion people live in unfamiliarly wet areas, and
~163 million people live in unfamiliarly dry areas now
• During last two decades, global glacier mass loss rate
exceeded 0.5 meters water equivalent year-1 (high confidence)
Gudmundsson L., …, Liu J., et al., 2021. Science 371: 1159-1162
Key Finding 1
Observed changes in river flows
and attribution
Intensification of the hydrological cycle due to human-induced climate change is
affecting physical aspects of water security (high confidence), thereby exacerbating
existing water-related vulnerabilities caused by other socioeconomic factors

9. Extreme weather events causing highly impactful floods and droughts have
become more likely and (or) more severe due to anthropogenic climate change
(high confidence)
• Anthropogenic climate change has
contributed to the increased
likelihood and severity of the impact
of droughts (high confidence)
• 7% of all disaster events worldwide
were drought-related from 1970 to
2019. They cause 34% of disaster-
related deaths
Key Finding 2
Current global drought risk
Hazard Vulnerability
Exposure Risk

10. • Between 1970 to 2019, 31% of all economic
losses were flood-related
• Several recent heavy rainfall events, such as
in western Europe, China, the United States,
Brazil and Australia that led to substantial
flooding, were made more likely by
anthropogenic climate change (high
confidence)
Key Finding 2
Risk of river flooding
Hazard
Vulnerability
Exposure
Risk
Projected
Historical
Extreme weather events causing highly impactful floods and droughts have
become more likely and (or) more severe due to anthropogenic climate change
(high confidence)

11. There is increasing evidence of observed changes in hydrological cycle on people
and ecosystems. A significant share of those impacts is negative and felt
disproportionately by already vulnerable communities (high confidence).
• Agriculture: approximately three-quarters of the
global harvested experienced yield losses
induced by meteorological drought from 1983
to 2009
• Energy production: thermoelectric and
hydropower production has been negatively
affected due to droughts (~4 to 5% reduction in
plant utilization rates during drought years)
Key Finding 3
Impacts of climate change on various sectors

12. Key Finding 3
• Ecosystems: loss and degradation of
freshwater ecosystems!also some culturally
significant terrestrial and freshwater species
and ecosystems in the Arctic, high mountain
areas (high confidence)
• Vulnerable communities: changes in water-
related hazards disproportionately impact
vulnerable, especially in the Global South
Impacts of climate change on various sectors
There is increasing evidence of observed changes in hydrological cycle on people
and ecosystems. A significant share of those impacts is negative and felt
disproportionately by already vulnerable communities (high confidence).

13. • Climate change impacts via water availability
changes are projected to increase
• Between 3 to 4 billion people are projected to be
exposed to physical water scarcity at 2℃ and
4℃ GWL, respectively (medium confidence)
• Streamflow in 42% to 79% of the world's
watersheds is projected to be affected by 2050
(medium confidence)
Water-related risks are projected to increase with every degree of global warming
(high confidence), and more vulnerable and exposed regions and peoples are
projected to face greater risks (medium confidence)
Key Finding 4
Streamflow changes at 1.5℃, 2℃ and 4℃ GWL

14. Key Finding 4
• Modified streamflow is projected to affect inflows
to urban storage reservoirs and increase the
vulnerability of urban water services to hydro-
meteorological extremes (high confidence)
• Expected impacts may be felt by roughly 1.5
billion people who are critically depend on run-off
from the mountains by the mid-21st century
(RCP6.0)
Regional synthesis of assessed changes
Water-related risks are projected to increase with every degree of global warming
(high confidence), and more vulnerable and exposed regions and peoples are
projected to face greater risks (medium confidence)

15. Key Finding 5
• Drought risks are projected to increase over the 21st century in many regions
• The global population exposed to extreme-to-exceptional total water storage drought
is projected to increase from 3% to 8% over the 21st century (RCP2.6-SSP2).
Pokhrel Y., … Liu J., et al., Nature Climate Change 11: 226–233
Population exposed
to extreme-to-
exceptional total
water storage drought
Area exposed to
extreme-to-exceptional
total water storage
drought
Drought and flood risks and societal damages are projected to increase with every
degree of global warming (medium confidence)

16. Key Finding 5
• Direct flood damages will increase by 4
to 5 times at 4 ℃ compared to 1.5 ℃
• At 4 ℃ GWL by the end of the century,
10 % of the global land area is
projected to face simultaneously
increasing high extreme streamflow and
decreasing low extreme streamflow,
affecting roughly over 2.1 billion people
Changes in river flooding under various scenarios
Drought and flood risks and societal damages are projected to increase with every
degree of global warming (medium confidence)

17. Key Finding 6
• Projected increases in hydrological extremes
pose increasing risks, with a potential
doubling of flood risk between 1.5 ℃ and 3
℃ of warming and an estimated 120% to
400% increase in population at risk of river
flooding at 2 ℃ and 4 ℃, respectively
• Extreme agricultural drought are projected to
be at least twice as likely at 1.5 ℃ GWL
Changes in likelihood of extreme agricultural drought
Limiting global warming to 1.5℃ would reduce water-related risks across regions
and sectors (high confidence)

18. Key Finding 6
• Projected losses include a 1.2 to 1.8-fold increase in GDP loss due to flooding
between 1.5 ℃ and 2 ℃ warming (medium confidence)
• Due to the combined effects of water and temperature changes, risks to agricultural
yields could be three times higher at 3 ℃ compared to 2 ℃ (medium confidence).
• In Mediterranean parts of Europe, hydropower potential reductions of up to 40% are
projected under 3 ℃ warming, while declines below 10% and 5% are projected
under 2 ℃ and 1.5 ℃ warming levels, respectively
• Climate-induced hydrological changes are projected to increase migration, with an
almost 7-fold increase in asylum seekers to the EU for RCP4.5 compared to RCP2.6
Limiting global warming to 1.5℃ would reduce water-related risks across regions
and sectors (high confidence)

19. Observed water adaptation responses have multiple benefits (high confidence), yet
evidence of effectiveness of adaptation in reducing climate risks is not clear due to
methodological challenges (medium confidence)
Key Finding 7
• A large share of adaptation interventions (~60%)
are shaped in response to water-related hazards
(high confidence)
• Adaptation responses in developing countries tend
to be autonomous
• Responses are more policy-oriented and urban-
focused in developed countries (high confidence)
Observed water-related adaptation response
Quality of evidence on water-related adaptation
response

20. Key Finding 7
• Water adaptation measures tend to have
positive economic and environmental outcomes
in developing and developed countries (high
confidence)
• A knowledge gap in knowing if observed
adaptation benefits also translate to climate risk
reduction, if so, by how much and under what
conditions (medium confidence).
Water-related adaptation response
Observed water adaptation responses have multiple benefits (high confidence), yet
evidence of effectiveness of adaptation in reducing climate risks is not clear due to
methodological challenges (medium confidence)

21. Future projected adaptations are effective in reducing risks to a varying extent
(medium confidence), but effectiveness falls sharply beyond 2 ℃, underscoring the
need for limiting warming to 1.5 ℃ (high confidence)
Key Finding 8
• Residual impacts remain for some options and
regions at all levels of warming, and the overall
effectiveness decreases at higher warming levels
• At warming levels beyond 1.5 ℃, the potential to
reach biophysical limits to adaptation due to limited
water resources are reported for Small Islands
(medium confidence) and regions dependent on
glaciers and snowmelt (medium confidence).
Effectiveness of water-related
Adaptation at different GWLs

22. Key Finding 9
• SDGs cannot be met without adequate and safe water
• Water is fundamental to all systems transition
• Water garners a significant share of public and private
adaptation funds, but barriers remain for low-income
countries to access funds
• Many mitigation measures, such as carbon capture and
storage, bio-energy, and afforestation and reforestation,
can have a high-water footprint (high confidence).
Liu et al. 2020. Resources, Conservation
and Recycling 154: 104565.
Water-Energy-Food Nexus
Water security is critical for meeting SDGs and climate-resilient development, yet
many mitigation measures have high water footprint which can compromise SDGs
and adaptation outcomes (high confidence)

23. Key Finding 10
• Many countries and social groups most threatened by climate change have contributed
the least to the problem and do not have the adequate resources to adapt (high
confidence)
• Water adaptation policies enabled through ethical co-production between holders of
Indigenous Knowledge, local knowledge and technical knowledge (medium confidence);
through cooperation and coordinated actions among multiple actors, including women
and all marginalized groups, at various levels of governance (medium confidence) is
needed for effective transitions towards Climate Resilient Development
A common set of enabling principles underpinned by strong political support can
help meet the triple goals of water security, sustainable and climate-resilient
development (high confidence)

24. @IPCC
Website: ipcc.ch
IPCC Secretariat: ipcc-sec@wmo.int
IPCC Press Office: ipcc-media@wmo.int
@IPCC_CH
linkedin.com/company/ipcc
F O R M O R E I N F O R M A T I O N : C O N N E C T W I T H U S :
Thanks!
Junguo Liu
liujg@sustech.edu.cn
SIXTH ASSESSMENT REPORT
Working Group II – Impacts, Adaptation, and Vulnerability
“The scientific evidence is unequivocal: climate change is a threat to
human wellbeing and the health of the planet”.
António Guterres, United Nations Secretary-General